Just Acquired an H-89A Not Powered Up for 20+ Years and Looking for Advice

[Jim Manley]

Hi everyone,

I just received an H-89A that hasn't been powered up for at least 20 years, it came with no boot disks, and I haven't even opened the case yet to see what the hardware configuration is.  I have downloaded the Usual Suspect user documentation, but haven't delved into looking for more advanced service-level docs until I know what's inside.

AIUI, the H-89A came with a hard-sectored, full-height floppy drive and, if this hasn't been upgraded to a soft-sectored drive, I'm gonna need to find some fresh bootable hard-sectored disks, and I hope others with applications and utilities beyond the stock set provided by Heathkit/Zenith.

I'm very experienced with hardware and software, including going back to 8-bit systems such as Altairs, IMSAIs, CompuPros, Osbornes, etc.  I can read schematics and solder very well and have the tools needed for advanced troubleshooting, such as multi-trace o-scopes, DVMs, freq counters, etc.  I'm very familiar with 8080 and Z-80 assembly language, CP/M, and the typical software development tools.  I just don't have any experience with these Heathkit/Zenith systems, HDOS, etc., and I describe my knowledge and experience as "Swiss cheesy" when it comes to them!

I do know to not power it up until I've opened it up and disconnected the power supply from the rest of the system, in case PS components may fail when subjected to full voltages and current.  I also know how to recondition large electrolytic capacitors starting with small voltage cycles at limited current.

I can verify that the PS is working to spec once I've taken those kinds of precautions, and expect to power up the other boards in sequence, starting with the motherboard.  I assume the assembly manuals have the usual outstanding Heathkit step-by-step troubleshooting sections for proceeding from first power all the way through booting the system.

As soon as I can get it opened up, do some disassembly, and take some photos, I'll upload them so that the experts can evaluate what's there and what recommendations you may have beyond what's in the assembly manuals.

Thanks in advance for any assistance that can be provided.  BTW, in addition to being a career Navy and Silicon Valley engineer with an MS in CS, I use 8-bit systems to teach CS hardware and software fundamentals to high school and college students.  In addition to using this system for that purpose, it will eventually be on loan as an operational, hands-on artifact to museums in the Southwest, starting in the Phoenix and Central Arizona areas.

All the Best,

Jim  KJ7JHE

[Jim Manley]

Some updates - after opening the shipping box, I discovered that it's actually a Heathkit/Zenith WH-89A.  It has a single H-17 double-density, full-height floppy drive, with a Z-89-37 floppy disk controller, so I understand that this is a 720K, soft-sectored, floppy drive (yay?).  I have NOS, blank, DS-DD, 5.25 disks in factory-sealed boxes, and I seem to recall that it's possible to write bootable H-17 disks in a 5.25-inch soft-sectored drive on a PC with the appropriate utility.

I'll provide more info after I open the computer up and photograph and examine the exact hardware inside.  I take it that the WH-89A was equipped with 64KB of DRAM, since it went for $1,695 in 1979 dollars (about $6,300 in 2020 dollars).

Thanks and All the Best,

Jim  KJ7JHE

[Mark Garlanger]

Hi Jim,

Welcome to the group.

On Sat, Dec 12, 2020 at 10:49 PM Jim Manley <jim.m...@gmail.com> wrote:

Some updates - after opening the shipping box, I discovered that it's actually a Heathkit/Zenith WH-89A.

Is there some label that says "WH-89A"? I would be surprised if that was the model number. The "W" part, means that it was "wired", and came assembled from the Heath Company. That was used before Zenith bought them. Once Zenith bought them, the assembled versions were called Z-89. The "-A" part was an updated version needed to meet FCC class-B rating. I thought the timing was that Zenith bought them out a while before the -A versions came out. Not a big deal, but it would be interesting to know if there was a WH-89A. 

All the various H-88/H-89/Z-90 were basically the same core, just different options for disk controllers/memory/etc.

 

  It has a single H-17 double-density, full-height floppy drive, with a Z-89-37 floppy disk controller, so I understand that this is a 720K, soft-sectored, floppy drive (yay?).  I have NOS, blank, DS-DD, 5.25 disks in factory-sealed boxes, and I seem to recall that it's possible to write bootable H-17 disks in a 5.25-inch soft-sectored drive on a PC with the appropriate utility.

I'll provide more info after I open the computer up and photograph and examine the exact hardware inside. 

Are you sure it's a Z-89-37? That last sentence sounds like you haven't opened it yet. Without opening it, there is no way to really know which controller it has. Heath sold 2 different drives for the H89 - the H-17-1 and H-17-4. The H-17-1 is single-sided, 40 track. The H-17-4 is double-sided, 80-track. The H-17-1 could be used with both the hard-sectored controller and the soft-sectored controller. With the hard-sectored, it could hold 100k. With soft-sectored, it can hold 160k. Officially the H-17-4 was only supported with the soft-sectored controller, but there was third-party software that allowed it to be used with the hard-sectored controller, and can hold 400k per disk. A catalog on my site shows both drives on page 3 of this catalog - https://heathkit.garlanger.com/catalogs/1982/Heathkit_Catalog_858.pdf

The H-17-1 is in the H-89, and the H-17-4 is in the external case to the left of the H-89.

If it does have the Z-89-37, you should be able to use Dave Dunfield's ImageDisk to create disks which will work on the H89.

I take it that the WH-89A was equipped with 64KB of DRAM, since it went for $1,695 in 1979 dollars (about $6,300 in 2020 dollars).

The WH-89 came with 48k, but upgradable to 64k, some versions of the Z-90 came with 64k standard, others were 48k.

Once you open and send some photos, we'll be able to identify what exactly you have.

Mark

 

Thanks and All the Best,

Jim  KJ7JHE

On Saturday, December 12, 2020 at 7:02:41 PM UTC-7 Jim Manley wrote:

Hi everyone,

I just received an H-89A that hasn't been powered up for at least 20 years, it came with no boot disks, and I haven't even opened the case yet to see what the hardware configuration is.  I have downloaded the Usual Suspect user documentation, but haven't delved into looking for more advanced service-level docs until I know what's inside.

AIUI, the H-89A came with a hard-sectored, full-height floppy drive and, if this hasn't been upgraded to a soft-sectored drive, I'm gonna need to find some fresh bootable hard-sectored disks, and I hope others with applications and utilities beyond the stock set provided by Heathkit/Zenith.

I'm very experienced with hardware and software, including going back to 8-bit systems such as Altairs, IMSAIs, CompuPros, Osbornes, etc.  I can read schematics and solder very well and have the tools needed for advanced troubleshooting, such as multi-trace o-scopes, DVMs, freq counters, etc.  I'm very familiar with 8080 and Z-80 assembly language, CP/M, and the typical software development tools.  I just don't have any experience with these Heathkit/Zenith systems, HDOS, etc., and I describe my knowledge and experience as "Swiss cheesy" when it comes to them!

I do know to not power it up until I've opened it up and disconnected the power supply from the rest of the system, in case PS components may fail when subjected to full voltages and current.  I also know how to recondition large electrolytic capacitors starting with small voltage cycles at limited current.

I can verify that the PS is working to spec once I've taken those kinds of precautions, and expect to power up the other boards in sequence, starting with the motherboard.  I assume the assembly manuals have the usual outstanding Heathkit step-by-step troubleshooting sections for proceeding from first power all the way through booting the system.

As soon as I can get it opened up, do some disassembly, and take some photos, I'll upload them so that the experts can evaluate what's there and what recommendations you may have beyond what's in the assembly manuals.

Thanks in advance for any assistance that can be provided.  BTW, in addition to being a career Navy and Silicon Valley engineer with an MS in CS, I use 8-bit systems to teach CS hardware and software fundamentals to high school and college students.  In addition to using this system for that purpose, it will eventually be on loan as an operational, hands-on artifact to museums in the Southwest, starting in the Phoenix and Central Arizona areas.

All the Best,

Jim  KJ7JHE

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[Douglas Miller]

Just to avoid some common points of confusion: The floppy drives, despite Heath's use of model numbers, are not restricted to a particular controller - they are just industry-standard floppy drives. The H17 *controller* was single-density only, but doesn't care if the drives are double-sided or 96tpi or even whether the diskettes are soft or hard sectored. The Z37 *controller* allowed either single or double density, but also did not care about number of sides or tracks. The Z37 controller chip (WD 1797) did not work with hard sectored diskettes. It then came down to the OS (drivers and utilities) to support things like double-sided and "double track", and in the H17 case hard sectored diskettes. For example, Magnolia Microsystems CP/M supported all drive types on the H17 controller, while I believe HDOS only supported single-sided single-track - at least for a long time.

So, how you create diskettes to use will depend on the *controller* as well as the capabilities of the OS. Z37-format diskettes can be created on a PC with the right kind of floppy drive, with some caveats. H17 diskettes can only be created on the Heath/Zenith computer, as far as I know. There is some special H/Z89 software/methods to download H17 diskette images and put them on H17 floppies.

[Glenn Roberts]

Jim: as Doug says, once we know exactly what drive/controller setup you have we can assess how to build bootable images for you. may or may not require hard sectored floppy disks…

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[Steven Feinsmith]

I suggest you be very careful with the power supply capacitors. The electrolytic capacitors tend to fail with blow the rubber lid. I may encourage you to use an autotransformer to start a very low voltage. You can increase the voltage by 10 volts per day until it reaches 120V. You happen to have an infra-red camera or laser thermometer to aim the capacitor cylinders to ensure that they do not develop heat build-up. It shows hot enough and then disconnects the power to avoid blow-up the capacitor and mess everything with an electrolytic chemical. Also, watch out for any tantalum capacitors too. You may see pretty dirty inside. Use air compressed to clean it. Sometimes, the connectors may tarnish. It will cause electrical contacts problem. In case if you see some option boards, remove them to the minimum as possible to avoid further damage. I hope my experience will help you to prevent components damage as possible when power is applied.

Good luck,

Steven

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[dwight]

Being that you have a 37 controller, your machine is soft sectored. Being that it has 64K, it likely also supports CP/M. Currently, the only way to create disk for soft sectored is to use an older computer that supports double density. It also needs a 360K drive ( 1.2Meg drives are not likely to work at creating 360K because of track width ).

Early on, I created code to bootstrap a hard sectored machine with a serial link. It required hand entering about 50 bytes of code to bootstrap with the ability to format and create hard sectored disk. It has been enhanced and expanded by others in this group ( Les Bird, mainly ).

It seems that as the number of, working, PCs with 360K capable drives is becoming rare. We might look at a similar serial method of creating a boot strap method for soft sectored. Soft sectored disk controllers are not all that hard to deal with. I'd think it is about time someone begins to look at a similar bootstrap for soft sectored disk. The system we have now can clearly be expanded to include soft sectored disk.

I'd work on such but at 73 years old, I have a number of other projects I'd like to complete that I think have higher priority. It is not that hard. Both Les and I understand the process and can help anyone that wants to take on such a project.

Dwight

---

From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Jim Manley <jim.m...@gmail.com>
Sent: Saturday, December 12, 2020 5:04 PM
To: SEBHC <se...@googlegroups.com>
Subject: [sebhc] Just Acquired an H-89A Not Powered Up for 20+ Years and Looking for Advice

 

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[Jim Manley]

Hi Mark, Douglas, Glenn, Steven, and Dwight,

Thanks for the quick responses - I wasn't sure how much anyone pays attention to Heathkit computers any more, given that I only saw 23 conversations here mostly going back at least 10 years, although the most recent was around June 2020.  I couldn't get any in-line photos within the post size limit, so if anyone needs the full-size photos, let me know and I'll e-mail them.

The original owner told me that it was a Heathkit H89A, and the docs that came with it include the "Model WH89 DIGITAL COMPUTER Operation/Service Manual 595-2272-01".  It has a beige cardstock cover with the "Zenith Data Systems" logo in the bottom 20% of the cover printed on it.  It has a cutout where the "Model WH89 DIGITAL COMPUTER" is printed on the first paper page underneath.  No assembly manuals are in the docs I was provided, further indicating that this is a WH-89 and it has a serial number tag that reads "H89A".

Although I have the original, full-size schematics, I would really like to get the H89 kit assembly manual(s), as the Operation/Service manual doesn't show how anything is put together, where the various interface boards are installed in a standard configuration, and other such very useful details, including drawings/photos.  I haven't been able to find an assembly manual anywhere on-line, although I suspect that Herb Johnson may have at least one original print version, as he's said that he has some docs in large black (Heathkit?) binders that have some mold on them, but the pages are intact.  I've dealt with Herb to acquire 8-inch floppies for my S-100 systems, and I've read his travails in bringing his H89s back to operating condition.

Now that I've looked closely at the other docs, one is the "Heathkit Manual for the 48 TPI, 5-1/4" FLOPPY DISK DRIVE Model H-17-1 595-2716" Copyright 1981 Heath Company.  However, another is the "Instructions for the HEATH ZENITH 96TPI, 5-1/4" FLOPPY DISK DRIVE Model H-17-5 Part No. 150-158" 597-3179-02 Copyright 1983 Heath Company.  The installed floppy drive has a Heath factory inspection date of 1985, so I strongly suspect this was purchased at a significant discount as the H/Z89 line was being discontinued after that date, and installed by the owner.

I haven't figured out how to get the floppy drive out, as the bezel on the front to the right moves back with the drive, but the bezel to the left seems to be retained in place by something behind it.  Opening the drive door partially or fully doesn't seem to have any effect.  Since the back of the drive is almost touching a vertical board to the left of the (main?) horizontal power supply board, it seems that the vertical board might need to be removed in order to allow the drive to move back sufficiently.  Only then will I be able to get to the interface boards plugged into the right side of what I assume is the motherboard.

There's also the "Installation Instructions for the  ZENITH | data systems DOUBLE-DENSITY DISK CONTROLLER Model Z-89-37" 595-2707-04" Copyright 1981 ZENITH DATA SYSTEMS.  At the moment, I've only been able to get in-situ photos of what I believe is the floppy controller board, but it seems to have later-series Western Digital ICs on it.  Oh, and there's also the words "DOUBLE DENSITY" silk screened on the board :)

Some additional great news is the installed 16K RAM expansion board, which means this system does have 64K of RAM.

If I had to guess, this system was built during the transition from the Heath Company to ZENITH DATA SYSTEMS.  It's clear that ZENITH slapped the cover on the original Heath Company Operations/Service document.  It's not obvious why there are Installation Instructions for both the H-17-1 and the H-17-5 drives, unless the system was upgraded to the H-17-5 by the owner.  Per the photo, the drive is full-height - well, width, I suppose, given the disk slot is oriented vertically - and the big door, which covers about half of the drive on the left side, extends and pivots along the full height of the disk slot.

Since it appears to have the -37 controller, I assume that a pair of double-density (double-sided?) half-height 5.25-inch drives could replace the single full-height drive, if a two drive cable is already in place, but one could be obtained/built, if needed.  I do have some old full-height 360K single-density PC drives ... somewhere.  I also have some Apple ][ 5.25-inch floppy drives, but I seem to recall (early versions of?) those have atypical ROMs that make them difficult/impossible to use for this kind of task.

Modulo a quarter-inch chunk gouged out of the lower-left edge of the case toward the rear, the system appears to be in very good shape and clean, as I think it was stored in a box behind/under many other artifacts from the same eras as those in the warehouse at the end of the "Indiana Jones" movie.  I'm an engineer, so I cast a jaundiced eye at the altar of the Devil's acolyte, Murphy, who is always sneaking around looking for ways to screw with everything and anything.  I'm a witness to exploding electrolytic and tantalum capacitors, not due to my malfeasance, but that of others (e.g., accidental shorting-out).

I'm also very aware of how brittle the kinds of plastics used in these systems can be as they age, as I've been a volunteer senior docent and restoration engineer at the Computer History Museum in Mountain View for going on 20 years.  I operated, maintained, and presented Babbage Difference Engine Version 2, Serial Number 2 when it was there for about eight years, where the operator isn't just the power supply, but the clock!  Mechanical inertia is critical to the timing of the movements of its parts - if you thought that was mostly the case for disk drives, you ain't seen nothin'!

Soooooo, it looks like if I can get some soft-sectored book disks, I can get started (following the power supply and other electrical checkouts being performed, of course).  A full set of utilities and applications not included on the boot disks would also be greatly appreciated, or at least the means for transferring files through the serial port, which I understand is available per one of the replies.

I'm a verrrrry happy camper but have had to lash myself to the mast, lest the siren songs and urgings of Scylla and Charybdis tempt me to just plug it into the wall ... and then have to call the fire department!  I'm also not so tempted since I don't have any boot disks, and it doesn't appear from on-line docs that the monitor is any more exciting than those on other contemporaneous late 1970s 8-bit systems.

Dwight - I might just be interested in your proposed project, after I've got this little gem glowing an emerald hue with recognizable characters in response to tippy-tapping on the keyboard.

All of the sage advice provided and yet to come is very much welcome and appreciated.  I think this is going to be a very straightforward mostly matter of testing, and it should just come up once it's been proven able to handle a heapin' helpin' of hospitality in the form of 120 VAC.

[Douglas Miller]

OK, so seems pretty certain you have the H/Z37 controller. The H17 controller does not have a Western Digital controller chip (only a synchronous serial chip) - and would not say "double density".

Note, this vintage of floppy drives have no ROM, or any sort of controller, on them. They simply pass-through the read/write signals with very little, generic, processing. And they have simple control signals for stepping the heads and motor on, and drive select, and status. So, most drives of that vintage are compatible, in the basic sense. I have heard rumors of incompatibilities with Apple ][ drives, though. Can't confirm that.

I guess there are lots of possibilities to explain the 96tpi drive manual. Likely the unit had more than one drive, and that could have been an external drive. It's even possible the drive in there now was simply a filler when the unit was sold, with 96tpi drive(s) being sold separately or re-purposed by the owner. A one-drive system is pretty cumbersome.

Beware that this vintage of drives does not use the IBM PC "cable twist" for drive select. Each drive must have a unique unit number set in the jumpers, and the cable must be straight-through. Good news is, that supports up to 4 drives. I'm not sure of the power supply implications of running two drives in the main cabinet. Others will need to comment on that. I know we ran a SASI HDD and controller, and some other power-hungry boards, but I don't recall all the limitations.

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[Jim Manley]

Hi Douglas,

Yep, I'm familiar with the vagaries of early disk drives, although I've never played with the signals down to the drive level on these models.  The jumpers that need to be set are on each drive, correct?

In addition to what Dwight mentioned, I've read some of the other threads where solid-state replacements for rotating disks for these systems have been adapted/developed, or at least attempted.  I would very much like to build/buy something like that, as the days for electro-magna-mechanical storage are numbered, and the count until end-of-life is decrementing at an accelerating rate, unfortunately.

I bought a 512K ("Fat") Mac when they came out, but I didn't buy an external drive.  I'd already witnessed the "floppy swappy" routine others with 128K of RAM in the Original Flavor Macs had to go through to do just about anything useful.  Instead, I bought RAM disk software that allowed me to establish virtual disks that were much faster than the physical ones.  I put the OS and applications on the RAM disk, since they didn't change (modulo version updates), as application data files did, so the latter were written to the physical drive.  As long as I didn't power down the Mac, I didn't have to reload the OS and applications during each work session.

Anywaaaaay, I'm looking forward to an H: prompt in the near future, and some A> prompts soon after that.  For now, I'm fooling around with Mark's H89 emulator.

Thanks and All the Best,

Jim  KJ7JHE

[dwight]

Hi Jim

Half height drives have the same 360K capabilities as the full height. Two drives are better than one.

The drive closer to the yoke does need better magnetic isolation, if modifying a machine with full height. Those that came with dual drives should be fine.

What other machines do you have? Do any have a 360K drive?

Dwight

---

From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Jim Manley <jim.m...@gmail.com>

Sent: Sunday, December 13, 2020 4:44 PM
To: SEBHC <se...@googlegroups.com>
Subject: Re: [sebhc] Re: Just Acquired an H-89A Not Powered Up for 20+ Years and Looking for Advice

 

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[Norberto Collado]

Power-up such system and replace any caps that failed (they will blow or burn out). As you have the Z37, just buy the Gotek controller and get some images from this team, boot up HDOS/CPM, and call it good for the day. Then add the floppy drives and test them with HDOS (TEST37).

GOTEK file attached to get you started.

Thanks,

Norberto

-------- Original Message --------
Subject: [sebhc] Just Acquired an H-89A Not Powered Up for 20+ Years and
Looking for Advice

From: Jim Manley <jim.m...@gmail.com>
Date: Sat, December 12, 2020 5:04 pm
To: SEBHC <se...@googlegroups.com>

Hi everyone,

I just received an H-89A that hasn't been powered up for at least 20 years, it came with no boot disks, and I haven't even opened the case yet to see what the hardware configuration is.  I have downloaded the Usual Suspect user documentation, but haven't delved into looking for more advanced service-level docs until I know what's inside.

AIUI, the H-89A came with a hard-sectored, full-height floppy drive and, if this hasn't been upgraded to a soft-sectored drive, I'm gonna need to find some fresh bootable hard-sectored disks, and I hope others with applications and utilities beyond the stock set provided by Heathkit/Zenith.

I'm very experienced with hardware and software, including going back to 8-bit systems such as Altairs, IMSAIs, CompuPros, Osbornes, etc.  I can read schematics and solder very well and have the tools needed for advanced troubleshooting, such as multi-trace o-scopes, DVMs, freq counters, etc.  I'm very familiar with 8080 and Z-80 assembly language, CP/M, and the typical software development tools.  I just don't have any experience with these Heathkit/Zenith systems, HDOS, etc., and I describe my knowledge and experience as "Swiss cheesy" when it comes to them!

I do know to not power it up until I've opened it up and disconnected the power supply from the rest of the system, in case PS components may fail when subjected to full voltages and current.  I also know how to recondition large electrolytic capacitors starting with small voltage cycles at limited current.

I can verify that the PS is working to spec once I've taken those kinds of precautions, and expect to power up the other boards in sequence, starting with the motherboard.  I assume the assembly manuals have the usual outstanding Heathkit step-by-step troubleshooting sections for proceeding from first power all the way through booting the system.

As soon as I can get it opened up, do some disassembly, and take some photos, I'll upload them so that the experts can evaluate what's there and what recommendations you may have beyond what's in the assembly manuals.

Thanks in advance for any assistance that can be provided.  BTW, in addition to being a career Navy and Silicon Valley engineer with an MS in CS, I use 8-bit systems to teach CS hardware and software fundamentals to high school and college students.  In addition to using this system for that purpose, it will eventually be on loan as an operational, hands-on artifact to museums in the Southwest, starting in the Phoenix and Central Arizona areas.

All the Best,

Jim  KJ7JHE

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[Steven Hirsch]

On 12/13/20 8:08 PM, Norberto Collado wrote:
> Power-up such system and replace any caps that failed (they will blow or burn
> out). As you have the Z37, just buy the Gotek controller and get some images
> from this team, boot up HDOS/CPM, and call it good for the day. Then add the
> floppy drives and test them with HDOS (TEST37).
>
> GOTEK file attached to get you started.

Seconded on the Gotek. For soft-sector floppy drive emulation it's a
reliable, cheap solution.

You can either purchase an install of HxC firmware for 10-Euro or use the
free-software FlashFloppy firmware. We can help you get that going if you
experience any problems.

[Mark Garlanger]

Hey Jim,

On Sun, Dec 13, 2020 at 5:09 PM Jim Manley <jim.m...@gmail.com> wrote:

Hi Mark, Douglas, Glenn, Steven, and Dwight,

Thanks for the quick responses - I wasn't sure how much anyone pays attention to Heathkit computers any more, given that I only saw 23 conversations here mostly going back at least 10 years, although the most recent was around June 2020.  I couldn't get any in-line photos within the post size limit, so if anyone needs the full-size photos, let me know and I'll e-mail them.

Not sure where you were looking, there is a lot of activity on the list. There is usually just a few day gap between messages on the list - https://groups.google.com/g/sebhc and sometimes many messages in a day. You should have been able to attach a few photos, provided the photos weren't too big. Feel free to send me photos directly, if you have any questions or want any feedback on what you have.

 

The original owner told me that it was a Heathkit H89A, and the docs that came with it include the "Model WH89 DIGITAL COMPUTER Operation/Service Manual 595-2272-01".  It has a beige cardstock cover with the "Zenith Data Systems" logo in the bottom 20% of the cover printed on it.  It has a cutout where the "Model WH89 DIGITAL COMPUTER" is printed on the first paper page underneath.  No assembly manuals are in the docs I was provided, further indicating that this is a WH-89 and it has a serial number tag that reads "H89A".

Although I have the original, full-size schematics, I would really like to get the H89 kit assembly manual(s), as the Operation/Service manual doesn't show how anything is put together, where the various interface boards are installed in a standard configuration, and other such very useful details, including drawings/photos.  I haven't been able to find an assembly manual anywhere on-line, although I suspect that Herb Johnson may have at least one original print version, as he's said that he has some docs in large black (Heathkit?) binders that have some mold on them, but the pages are intact.  I've dealt with Herb to acquire 8-inch floppies for my S-100 systems, and I've read his travails in bringing his H89s back to operating condition.

There are scans of the assembly manuals here - https://bitbucket.org/HeathkitGuy/heathkitinformation/src/master/

 

 

Now that I've looked closely at the other docs, one is the "Heathkit Manual for the 48 TPI, 5-1/4" FLOPPY DISK DRIVE Model H-17-1 595-2716" Copyright 1981 Heath Company.  However, another is the "Instructions for the HEATH ZENITH 96TPI, 5-1/4" FLOPPY DISK DRIVE Model H-17-5 Part No. 150-158" 597-3179-02 Copyright 1983 Heath Company.  The installed floppy drive has a Heath factory inspection date of 1985, so I strongly suspect this was purchased at a significant discount as the H/Z89 line was being discontinued after that date, and installed by the owner.

I haven't figured out how to get the floppy drive out, as the bezel on the front to the right moves back with the drive, but the bezel to the left seems to be retained in place by something behind it.  Opening the drive door partially or fully doesn't seem to have any effect.  Since the back of the drive is almost touching a vertical board to the left of the (main?) horizontal power supply board, it seems that the vertical board might need to be removed in order to allow the drive to move back sufficiently.  Only then will I be able to get to the interface boards plugged into the right side of what I assume is the motherboard.

It's been a while since I took one out, but I believe the drive gets pushed out the front.  

 

There's also the "Installation Instructions for the  ZENITH | data systems DOUBLE-DENSITY DISK CONTROLLER Model Z-89-37" 595-2707-04" Copyright 1981 ZENITH DATA SYSTEMS.  At the moment, I've only been able to get in-situ photos of what I believe is the floppy controller board, but it seems to have later-series Western Digital ICs on it.  Oh, and there's also the words "DOUBLE DENSITY" silk screened on the board :)

Some additional great news is the installed 16K RAM expansion board, which means this system does have 64K of RAM.

If I had to guess, this system was built during the transition from the Heath Company to ZENITH DATA SYSTEMS.  It's clear that ZENITH slapped the cover on the original Heath Company Operations/Service document.  It's not obvious why there are Installation Instructions for both the H-17-1 and the H-17-5 drives, unless the system was upgraded to the H-17-5 by the owner.  Per the photo, the drive is full-height - well, width, I suppose, given the disk slot is oriented vertically - and the big door, which covers about half of the drive on the left side, extends and pivots along the full height of the disk slot.

Since it appears to have the -37 controller, I assume that a pair of double-density (double-sided?) half-height 5.25-inch drives could replace the single full-height drive, if a two drive cable is already in place, but one could be obtained/built, if needed.  I do have some old full-height 360K single-density PC drives ... somewhere.  I also have some Apple ][ 5.25-inch floppy drives, but I seem to recall (early versions of?) those have atypical ROMs that make them difficult/impossible to use for this kind of task.

Old 360K drives should work, but the H-17-4/-5 drives were 720K (or a bit higher depending on the sector size/number of sectors). So if you do find software on 96 tpi disks, you would not be able to read them.

 

Modulo a quarter-inch chunk gouged out of the lower-left edge of the case toward the rear, the system appears to be in very good shape and clean, as I think it was stored in a box behind/under many other artifacts from the same eras as those in the warehouse at the end of the "Indiana Jones" movie.  I'm an engineer, so I cast a jaundiced eye at the altar of the Devil's acolyte, Murphy, who is always sneaking around looking for ways to screw with everything and anything.  I'm a witness to exploding electrolytic and tantalum capacitors, not due to my malfeasance, but that of others (e.g., accidental shorting-out).

I'm also very aware of how brittle the kinds of plastics used in these systems can be as they age, as I've been a volunteer senior docent and restoration engineer at the Computer History Museum in Mountain View for going on 20 years.  I operated, maintained, and presented Babbage Difference Engine Version 2, Serial Number 2 when it was there for about eight years, where the operator isn't just the power supply, but the clock!  Mechanical inertia is critical to the timing of the movements of its parts - if you thought that was mostly the case for disk drives, you ain't seen nothin'!

Soooooo, it looks like if I can get some soft-sectored book disks, I can get started (following the power supply and other electrical checkouts being performed, of course).  A full set of utilities and applications not included on the boot disks would also be greatly appreciated, or at least the means for transferring files through the serial port, which I understand is available per one of the replies.

I have IMD images on my site: HDOS - https://heathkit.garlanger.com/software/library/Heath/HDOS/ and CPM - https://heathkit.garlanger.com/software/library/Heath/CPM/ If you a system that supports ImageDisk, you should be able to write them to new disks. 

 

I'm a verrrrry happy camper but have had to lash myself to the mast, lest the siren songs and urgings of Scylla and Charybdis tempt me to just plug it into the wall ... and then have to call the fire department!  I'm also not so tempted since I don't have any boot disks, and it doesn't appear from on-line docs that the monitor is any more exciting than those on other contemporaneous late 1970s 8-bit systems.

Dwight - I might just be interested in your proposed project, after I've got this little gem glowing an emerald hue with recognizable characters in response to tippy-tapping on the keyboard.

All of the sage advice provided and yet to come is very much welcome and appreciated.  I think this is going to be a very straightforward mostly matter of testing, and it should just come up once it's been proven able to handle a heapin' helpin' of hospitality in the form of 120 VAC.

All the Best,

Jim  KJ7JHE

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[Jim Manley]

Hi Dwight,

I have an ancient Compaq "haulable" with two 360 K drives, an Osborne 1 with two full-height 360K drives, a few 286 and 386 PCs, half-a-dozen, or so, loose 360K drives in boxes somewhere (I recently moved 8,000+ pounds of household goods 1,200 miles myself), and some Apple ][ "130K" drives that are electro-mechanically the same as the earlier PC 360K drives, but are effectively "dumbed down" to 130K by the Original Flavor Apple DIsk ][ controller board.  Of course, it's how the bits are laid down on the floppies that counts, not their theoretical maximum capacity.

Not many people know that, once we got to 1.44 MB 3.5-inch floppies and the hard drives of that same vintage, the magnetic flux densities that could be written were so intense that they can't be completely erased through bulk degaussing.  I can't talk about the details here, but it's possible to recover multiple generations of writes to magnetic media at that level of flux densities (and above, of course).  Such media has to be physically destroyed to ensure data on it is completely inaccessible.

I guess mu-metal (nickel-iron) is used to shield large-strength fields, so I may need to find some of that, probably in some old highly-integrated electronic systems (e.g., "luggable" computers and other field equipment).

I found the pages for the Semi-Virtual Drive, but it appears that Eric is no longer offering it, even though the ordering page still exists (although the secret words aren't displayed, so orders can't be submitted).

Thanks and All the Best,

Jim  KJ7JHE

[dwight]

I'm curious, did you ever erase disk with a super magnet. I've looked at the output of the read amp after doing that and I can't see anything except background noise. I do agree that erasing with a drive is not complete but once the media is all previous data is gone.

Dwight

---

From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Jim Manley <jim.m...@gmail.com>

Sent: Sunday, December 13, 2020 7:17 PM

To: SEBHC <se...@googlegroups.com>
Subject: Re: [sebhc] Re: Just Acquired an H-89A Not Powered Up for 20+ Years and Looking for Advice

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[Jim Manley]

Back in the first season or two of Mythbusters, they investigated whether eelskin wallets were scrambling the mag stripes on credit/etc. cards, and they proved that no eel, even electric eels, could generate enough of an EM field to affect them.  They then checked to see if the magnetic clasps typically used in those wallets could be responsible, but they weren't even close to being powerful enough to cause any read errors.  So, they kept going and had to use a very powerful electromagnet to start creating read errors.  That was about 30 years ago, and a lot has happened since then.

I did lots of R&D work in the Navy with DARPA and in SillyCon Valley in all sorts of interesting areas.  The National Institute of Standards and Technology and a certain TLA (Three Letter Acronym :) agency have extreme interests in this area, and have done a bunch of experiments (through particular labs via highly classified contracts) over time, and they use the most powerful magnets on the planet for their work.  They also use the equivalent of scanning probe microscopy (similar to atomic force microscopy used to move individual atoms around to build atomic scale nanomachines, and originally spell IBM and THINK in atoms) that works in the magnetic domain to measure and manipulate fields down towards that scale.

The last I read, they still don't know what the limit for magnetic flux density for data storage is, and could theoretically keep building rotating electromagnetic storage (RES) with higher-and-higher numbers of bit bits per area.  However, the cost advantage of SSDs (especially wrt mechanical reliability and redundancy/maintenance/replacement costs) has been steadily eroding the density advantages of RES, starting at the low-cost end.

All the Best,

Jim  KJ7JHE

[Jim Manley]

Hi Mark,

On Sunday, December 13, 2020 at 7:22:57 PM UTC-7 Mark Garlanger wrote:

Not sure where you were looking, there is a lot of activity on the list. There is usually just a few day gap between messages on the list - https://groups.google.com/g/sebhc and sometimes many messages in a day. You should have been able to attach a few photos, provided the photos weren't too big. Feel free to send me photos directly, if you have any questions or want any feedback on what you have.

I was looking for posts about H89s, and this series of conversations seemed to be the only show in town.  I haven't looked at every series, so if there are others, I'll scan through them.

I got tired of shrinking the photos multiple times, and at that point, the details desired to be displayed weren't visible.

 

There are scans of the assembly manuals here - https://bitbucket.org/HeathkitGuy/heathkitinformation/src/master/

Thanks - sometimes, Google just sucks!

 

It's been a while since I took one out, but I believe the drive gets pushed out the front.  

When I was able to look at the assembly manual, I realized that the two screws on top of the drive that hold the mu-metal shield down are also holding the drive from moving out of the frame ... and the case.  One had worked most of its way out of its hole during transport and I screwed it back down!

Old 360K drives should work, but the H-17-4/-5 drives were 720K (or a bit higher depending on the sector size/number of sectors). So if you do find software on 96 tpi disks, you would not be able to read them.

 

OK, that makes sense and is good to know.

I have IMD images on my site: HDOS - https://heathkit.garlanger.com/software/library/Heath/HDOS/ and CPM - https://heathkit.garlanger.com/software/library/Heath/CPM/ If you a system that supports ImageDisk, you should be able to write them to new disks. 

I'm familiar with those and have a system somewhere in storage that can handle them, or if I can't find it soon enough, I can build another one.

Thanks and All the Best,

Jim  KJ7JHE

[Steven Hirsch]

On 12/13/20 10:17 PM, Jim Manley wrote:

> I found the pages for the Semi-Virtual Drive, but it appears that Eric is
> no longer offering it, even though the ordering page still exists (although
> the secret words aren't displayed, so orders can't be submitted).

Hi, Jim.

The SVD is a handy piece of equipment, but you would strictly need it only if
you want to emulate hard-sector H17 diskettes. For soft-sector formats take a
look at Gotek (HxC or FlashFloppy firmware) or HxC hardware (a bit dated now).
For current solution to hard-sector emulation there is DREM.

For HDD emulation there is mfmemu or DREM.

[Jim Manley]

Hi Steven and Norberto,

Thanks for the Gotek pointers and there's one en route (I already have the cable) and it should be here by Wednesday ... or Thursday ... or Friday ... or Saturday.  I've detected a strong disturbance in The Force ... and it looks like it's due to The Late Christmas Shopping/Shipping Effect.  I'm about halfway between Phoenix and the Grand Canyon, and we're still served by stagecoaches ... occasionally.  I think the burros in The Big Ditch get stuff before we do here.

All the Best,

Jim  KJ7JHE

[Norberto Collado]

As the Gotek weights less than 150 pounds, at least the Burros should be able to bring them to your home before the weekend. Make sure you have a nice cold beer ready to drink before starting to debug the system to clear-up the mind. I went to the Grand Canyon, and never saw any Burros in the wild. Next time, I need to check Beatty’s “Happy Burro Chili and Beer” to try their acclaimed chili recipe.

 

Thanks,

Norberto

 

From: "se...@googlegroups.com" <se...@googlegroups.com> on behalf of Jim Manley <jim.m...@gmail.com>
Reply-To: "se...@googlegroups.com" <se...@googlegroups.com>
Date: Monday, December 14, 2020 at 9:10 AM
To: "se...@googlegroups.com" <se...@googlegroups.com>
Subject: Re: [sebhc] Re: Just Acquired an H-89A Not Powered Up for 20+ Years and Looking for Advice

 

Hi Steven and Norberto,

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[Jim Manley]

So, in looking at the H89 Operation Manual, it looks like the motherboard has to be pulled in order to set the primary and secondary power-up configurations.  Any particular values for switches S401 and S402 that are the best to use starting out, since I won't be able to boot from a floppy for a while?  It looks like the initial settings for the serial port are 9600N full-duplex.

SW501 should be OK, since it's set up based on the disk drive, the same for JJ501 - 503 for RAM, and for JJ504 - 507 for system PROM.  The serial port interrupt jumpers for RST3/4/5 seem like they should all be disconnected. 

Norberto - is there any truth to the rumor that you created a USB interface for the H-89 that allows it to be booted from, or at least access, USB floppy, hard disk, and/or thumb drives?  Enquiring burros want to know! :D

Thanks and All the Best,

Jim  KJ7JHE

[Glenn Roberts]

Norberto built a version of a serial/USB interface for the H89

 

http://koyado.com/Heathkit/H-89_USB_Serial.html

 

Unfortunately it appears Norberto doesn’t have any more blank boards (?)

 

Like all of Norberto’s USB interfaces, this uses the FTDI VDIP-1 USB Host Controller breakout board

 

https://www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_VDIP1.pdf

 

This board knows all the “smarts” of the USB I/O protocols and presents a simple command language for accessing them, which I’ve built an API front end for on the H8/89 side.  I’ve written a number of utilities to copy files to/from the machine using this interface. See “VDIP1 Utilities for HDOS - By Glenn” on that page, so YES you can definitely move files in and out using USB thumb drives (or any USB-compatible drive for that matter).

 

I believe I need to go back and clean these programs up. Steven Hirsch, George Farris and I were working on some improvements to the CP/M version and I need to make sure we have versions that work for the different port configurations we have.  This all got back-burnered over the summer… ☹

 

I believe Douglas Miller has worked on some new ROM features that will allow the new Z80 Rev 4.0 board boot from a USB device using the VDIP interface??  If so that’s forthcoming (but presumably not backward compatible with the H89…?)

 

 

 

From: se...@googlegroups.com <se...@googlegroups.com> On Behalf Of Jim Manley
Sent: Monday, December 14, 2020 6:15 PM
To: SEBHC <se...@googlegroups.com>
Subject: Re: [sebhc] Re: Just Acquired an H-89A Not Powered Up for 20+ Years and Looking for Advice

 

So, in looking at the H89 Operation Manual, it looks like the motherboard has to be pulled in order to set the primary and secondary power-up configurations.  Any particular values for switches S401 and S402 that are the best to use starting out, since I won't be able to boot from a floppy for a while?  It looks like the initial settings for the serial port are 9600N full-duplex.

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[Douglas Miller]

Note that the VDIP-1 module easily supports FAT filesystems on USB-connected storage, for file transfers. There are variations of VDIP-1 firmware to support certain other USB peripherals, but I'm not aware of the OS support for those (yet). The new H8-Z80 board with expanded ROM can run stand-alone utilities, and can boot, off the USB storage as well. I owe the group a stand-alone version of the H8D utility to image hard-sectored diskettes without requiring a host PC (other than to create files on the USB storage). That should simplify the process of creating H17 diskettes - for those that generously offer to do it for the rest.

While these expanded features are not yet available on the H89, Norberto and I did discuss a scheme to do that (see attached). However, it's just in concept stage at this time. If there were a simple way to expand the H89 ROM (some sort of small daughter board), we might be able to provide some of these features sooner.

To view this discussion on the web visit https://groups.google.com/d/msgid/sebhc/030a01d6d280%24ffff0c00%24fffd2400%24%40gmail.com.

[Jim Manley]

Hi Glenn,

What a coinky-dink, I just read an article by someone named Dr. Glenn Roberts on the Jameco.com site, relating his Love H8 relationship with his Heathkit computer of Ancient Lore! :D  BTW, I'm a pilot and am very interested in the FAA ATC modernization program with which you were associated (led?) when you wrote the Jameco article (and still are?).

I can have more boards made for Norberto's USB interface.  In any case, I look forward to whatever updates may be forthcoming on the software side of the project, and perhaps someday I can contribute after I get my H-89 up and running.

Thanks and All the Best,

Jim  KJ7JHE

[Norberto Collado]

Norberto - is there any truth to the rumor that you created a USB interface for the H-89 that allows it to be booted from, or at least access, USB floppy, hard disk, and/or thumb drives?  Enquiring burros want to know! :D

 

Glenn and Douglas are the experts on the H8/H89 USB interface, I will defer to them for guidance. I think what makes more sense is to get you the H89-Z67 board, so that you can boot from the hard drive as you have the Z37 already installed. Let me see if I do have some spares.

 

Douglas and I have did work on adding the H89 the same capabilities that we have in the H8. I did work on it to get the mechanical alignment and what is pending is the actual board layout. I’m still debating if it will be better to design a new H89 board using the H8 Z80 board design as it has the EEPROM flash capabilities + USB + Network… As I’m refreshing now the H8, then we can go back to the H89 when done.

 

Also Terry as been refreshing the H89, so check with him as well on what is available.

 

Thanks,

Norberto

 

From: "se...@googlegroups.com" <se...@googlegroups.com> on behalf of Jim Manley <jim.m...@gmail.com>
Reply-To: "se...@googlegroups.com" <se...@googlegroups.com>
Date: Monday, December 14, 2020 at 3:15 PM
To: "se...@googlegroups.com" <se...@googlegroups.com>
Subject: Re: [sebhc] Re: Just Acquired an H-89A Not Powered Up for 20+ Years and Looking for Advice

 

So, in looking at the H89 Operation Manual, it looks like the motherboard has to be pulled in order to set the primary and secondary power-up configurations.  Any particular values for switches S401 and S402 that are the best to use starting out, since I won't be able to boot from a floppy for a while?  It looks like the initial settings for the serial port are 9600N full-duplex.

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[Glenn Roberts]

Ah yes. I posted that article here when I wrote it but we have many new members, heres’ the link

 

https://www.jameco.com/Jameco/workshop/MyStory/heathkit.html

 

As for my connection to aviation, I served as Chief Engineer for an organization called the Center for Advanced Aviation System Development (CAASD), a Federally-Funded R&D center operated by The MITRE Corporation in McLean VA and sponsored by the Federal Aviation Administration. CAASD serves as an R&D laboratory for future technologies and procedures in air traffic management. I oversaw the development of a human-in-the-loop simulation laboratory that tested new concepts with live pilots and controllers. Later I led our independent R&D work and technology transfer functions. Many of the technologies and procedures we developed have gone on to be widely implemented. We played a big part, for example, in developing and fielding Automatic Dependent Surveillance-Broadcast (ADS-B). Autonomous flight (and ground transportation) also were a big part of what I was involved in. I began a phased retirement in February 2018 and am now fully retired. In 2019 my wife and I moved from Northern Virginia to Lewes Delaware, a beach town on the DelMarVa peninsula.

 

On the Heathkit front, this summer I seem to have been preoccupied with hardware activities having built out an SVD and Norberto’s 8080 64K RAM board, plus finally getting a Z80 (Rev. 2.6) board working that had been 95% done. Also restored an H9 terminal to like-new and worked on distributing software and disks from my Virginia rescue” trip in June. Right now, as you’ve seen from my posts, I’m building out some of the new I/O boards (and probably the Wiznet board next!)

 

But I do have an IOU to the group to clean up, baseline and document the software utilities for the USB/VDIP interface, which is a prominent feature of the new boards that Norberto and Douglas have put together. I will do that…

 

• Glenn

 

 

From: Jim Manley <jim.m...@gmail.com>
Sent: Monday, December 14, 2020 11:07 PM
To: se...@googlegroups.com; glenn.f...@gmail.com
Subject: Re: [sebhc] Re: Just Acquired an H-89A Not Powered Up for 20+ Years and Looking for Advice

 

Hi Glenn,

[Jim Manley]

Hi Guys,

I found my autotransformer, so I will be starting reconditioning of the power supply capacitors today.  The Gotek will allegedly be arriving by Friday, so that will be good timing, as the power supply and other boards should have passed power-up testing by then (or, I'll have a passel of dead caps to replace, some of which I won't have a replacement for and would need to order, of course).

In the meantime, there's an H-89 on ePrey for about $350 including shipping, and it looks pretty clean (item number 164280112702).  It can't be powered up for testing, supposedly because the fuse and holder cap are missing, but I don't know whether that's just a ruse where they tested it, found problems, and then "lost" the fuse and holder cap.

It doesn't appear to have a 16K expansion board, so should just have 48K, and I can't see which boards are in the right-side card cage, other than the serial interface.  It does have a floppy drive of unknown type, but it looks like an H-17 style with the large door.  There aren't any photos to suggest which controller board it has, or whether it even has one.  I can ask for additional photos, of course.

Is that a reasonable price, considering the possibilities, one of which is that everything is dead and I'd need to repair/replace all of the electronics?

Thanks and All the Best,

Jim  KJ7JHE

On Sat, Dec 12, 2020 at 7:02 PM Jim Manley <jim.m...@gmail.com> wrote:

Hi everyone,

I just received an H-89A that hasn't been powered up for at least 20 years, it came with no boot disks, and I haven't even opened the case yet to see what the hardware configuration is.  I have downloaded the Usual Suspect user documentation, but haven't delved into looking for more advanced service-level docs until I know what's inside.

AIUI, the H-89A came with a hard-sectored, full-height floppy drive and, if this hasn't been upgraded to a soft-sectored drive, I'm gonna need to find some fresh bootable hard-sectored disks, and I hope others with applications and utilities beyond the stock set provided by Heathkit/Zenith.

I'm very experienced with hardware and software, including going back to 8-bit systems such as Altairs, IMSAIs, CompuPros, Osbornes, etc.  I can read schematics and solder very well and have the tools needed for advanced troubleshooting, such as multi-trace o-scopes, DVMs, freq counters, etc.  I'm very familiar with 8080 and Z-80 assembly language, CP/M, and the typical software development tools.  I just don't have any experience with these Heathkit/Zenith systems, HDOS, etc., and I describe my knowledge and experience as "Swiss cheesy" when it comes to them!

I do know to not power it up until I've opened it up and disconnected the power supply from the rest of the system, in case PS components may fail when subjected to full voltages and current.  I also know how to recondition large electrolytic capacitors starting with small voltage cycles at limited current.

I can verify that the PS is working to spec once I've taken those kinds of precautions, and expect to power up the other boards in sequence, starting with the motherboard.  I assume the assembly manuals have the usual outstanding Heathkit step-by-step troubleshooting sections for proceeding from first power all the way through booting the system.

As soon as I can get it opened up, do some disassembly, and take some photos, I'll upload them so that the experts can evaluate what's there and what recommendations you may have beyond what's in the assembly manuals.

Thanks in advance for any assistance that can be provided.  BTW, in addition to being a career Navy and Silicon Valley engineer with an MS in CS, I use 8-bit systems to teach CS hardware and software fundamentals to high school and college students.  In addition to using this system for that purpose, it will eventually be on loan as an operational, hands-on artifact to museums in the Southwest, starting in the Phoenix and Central Arizona areas.

[geneb]

On Wed, 16 Dec 2020, Jim Manley wrote:

> Hi Guys,
>
> I found my autotransformer, so I will be starting reconditioning of the
> power supply capacitors today. The Gotek will allegedly be arriving by
> Friday, so that will be good timing, as the power supply and other boards
> should have passed power-up testing by then (or, I'll have a passel of dead
> caps to replace, some of which I won't have a replacement for and would
> need to order, of course).
>

Before powering it up, I'd really recommend you replace all the 2.2uF &
4.7uF tantalum capacitors on both the TLB & CPU boards. After you've done
that, you can boot the machine into the RAM test by setting SW 5 to on (I
think). That will kick off the RAM test that's built into the monitor
ROM. If memory serves, 64k is going to count to 377777 (octal). If it
passes the RAM test a few times, you should be good to go.

I'd also set the machine to local mode and test to make sure all the keys
work.

g.



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[Bob Groh]

Re: eBay H-89

Does seem like a good deal - but, in today's somewhat hyper prices, somewhat suspiciously underpriced? It is a somewhat later H-89 in that the bottom enclosure is a later version with a separate aluminum panel for the IO, etc. As you indicated, most likely does not work. No documents either or disks, etc.

Re: powering up your H-89.

As others have indicated, if a tantalum cap hasn't blown up yet, it will, most likely, do so.  So I would certainly get a supply of 2.2 uF and 10 uF modern electrolytic (someone must have a list someplace) and plan on a happy day or so replacing ALL of the tantalum. The power supply caps should also be replaced and I would turn on the PS with none of the boards connected to just make sure everything is up and running.  Putting a bit of a load on each of the major voltage outputs might also be a wise thing.  You would hate to have a bad power supply and have it take out stuff on the big boards.

Bob Groh, Blue Springs, MO. 

Old Heathkit guy from back in the day.

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[Steven Hirsch]

On 12/16/20 4:08 PM, Bob Groh wrote:

> Re: powering up your H-89.
> As others have indicated, if a tantalum cap hasn't blown up yet, it will,
> most likely, do so. So I would certainly get a supply of 2.2 uF and 10 uF
> modern electrolytic (someone must have a list someplace) and plan on a
> happy day or so replacing ALL of the tantalum.

This indeed. There are two types of early-80s tantalum caps: those that have
failed and those that are about to.

[Glenn Roberts]

IMO “free shipping” isn’t always necessarily such a good thing. It means the seller is paying for shipping out of their profit so they are incentivized to go the cheapest route.

Shipping an H89 properly is neither trivial nor cheap so make sure you agree up front on how it will be packed and shipped

Sent from my iPad

> On Dec 16, 2020, at 5:04 PM, Steven Hirsch <snhi...@gmail.com> wrote:

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[Mark Garlanger]

That H89 has been listed at least since July, based on the revision history. Not in good condition, and at $275, definitely not worth it to me, even though it is local for me and I could avoid the shipping cost. Fixing the fuse would also be a big hassle. 

BTW, Jim, I tried to respond to your direct message, but google returned it with an "The email account that you tried to reach does not exist." error.. even though I just did a reply to your email. No idea why.

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[Jim Manley]

Thanks for the responses, everyone!

I did note that I was going to disconnect the PS from everything else before I did any reconditioning and testing with it.

In general, the number one sin committed with capacitors is using components at more than half of their rated voltage.  As with many circuit design (as well as in other engineering disciplines) maxims, more headroom is always better.  The British Comet airliner disasters , where windows blew out at altitude, were due to civil engineering margins of safety (4:1) being applied to the much-higher cyclic stress environment of aeronautical engineering, where 10:1 is the acceptable minimum margin (too-sharp corners in the windows that concentrated airframe and skin stresses also contributed to failure).

Electrolytic capacitors can generally be reconditioned with a slow-enough increases in cyclic voltage and current values.  At the risk of preaching to the choir, they have an electrolyte "skin" that's formed during manufacturing and is retained through normal use.  The rate at which reconditioning can be performed is determined by monitoring charge current (effectively, internal resistance, which increases with skin formation, IIRC), and as long as you don't proceed faster than indicated by the charge rate, it usually succeeds.

If you can't eventually get to the rated voltage because the charge current it wants remains too high, then the cap is unrecoverable, but I've seen cases where a week, or more, resulted in a satisfactory reconditioning.  It comes down to how much someone's time is worth, and right now, my rate's pretty cheap!  Besides, it takes so long for stuff to get here that I might as well have something to do while waiting.  It would normally be the kind of busy work that students would be given to see how serious they are about learning electronics, but COVID-19 currently requires that we invent transporter and replicator technologies in order for them to get their hands on equipment while we can't meet for classes and labs.

Tantalums are a whole 'nother story, but like all things, where you stand depends on where you sit.  Tantalums can be used in applications such as audio with impunity, but when they're used in power applications, the words "Abandon All Hope Ye Who Enter Here" can be prophetic.  However, I've observed the voltage overhead rule violated frequently with these kinds of parts.

Thanks for the data point on the ePrey H-89 being Out There since July.  The fuse holder cap missing is an easy fix, even if I just replace the holder, for which I'd probably have to buy an entire one just to get a cap anyway.  With a second (working soon, maybe?) H-89 next to it, it should be pretty easy to isolate issues, assuming killer things (like old tantalums shorting) are dealt with first.  Just out of curiosity, has anyone attempted to reverse-engineer the PCBs in the H-89?  They're two-layer, AIUI, and I know a lot's been done to develop H8 boards, albeit with new features not in the Original Flavor systems.

If you haven't seen it on the news, Google has been having outages for several days worldwide that they haven't said anything about as to why, but it's making some accounts inaccessible, appear to not exist, etc., for varying periods of time.

More to Come, So Stay Tuned ...

Jim  KJ7JHE