some new challenges

[Glenn Roberts]

I'll step out of the shadows... i'm the buyer of Bill Loguidice's heathkit collection announced here recently.  I drove up to NJ yesterday to pick it up.  I wanted to thank Bill publicly for offering it for sale here first and for his professionalism in working with me.

 

One project that I hope to bring to conclusion is his H8-2000.  He worked with Jack Rubin and Les Bird to assemble a set of boards and these hopefully are nearly complete and operational (Jack says most are smoke tested but not functionally tested yet).  I'll attempt to bring that project home.  Also in the collection is a bare board for Norberto's Z67 IDE.

 

He also included a non-operational H89 that I'm trying to diagnose.  It gives a single beep when powered up and i get raster and a blinking cursor but no prompt or keyboard response.  any thoughts on how to walk through the troubleshooting process would be appreciated. 

 

Thanks all, especially Bill!

 

- Glenn

 

 

[Kenneth L. Owen]

Hi Glenn,

On the H-89, power it up with the on/off Line key pressed.  If the terminal is working properly, you should get just one beep.  While still Off-Line, typing on the keyboard should give what you type on the screen.  If all of this works, then the terminal is working.

With the off-line key up, you should get TWO beeps on power up.  If all of the tests on the terminal were good, then just one beep probably means the problem is on the CPU board and it is not initializing to send the second beep.

A quick check is:
Power:
Check output on the three regulators at the power supply (+5, +5 and +12.
Next check the power plug to CPU card.
IF the above are good, check the output of the regulators on the CPU card (across the top of the card and mounted on the metal head piece).  If one of these is reading bad, then you probably have a bad tantrum capacitor (I know it is tantalum, but in a Heath they are tantrums).

-- ken

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[Glenn]

tx ken. i forgot to mention, no keyboard response regardless of on line vs off line.

 

i agree first thing to look at is the power and the "tantrums" - good advice (though no visible damage to them that I could see).  thanks!

 

- glenn

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[Lee Hart]

On 7/25/2012 5:49 AM, Glenn Roberts wrote:
> I'll step out of the shadows... i'm the buyer of Bill Loguidice's
> heathkit collection announced here recently. I drove up to NJ yesterday
> to pick it up. I wanted to thank Bill publicly for offering it for sale
> here first and for his professionalism in working with me.

You have my thanks and appreciation as well! These computers are a piece
of history. If we don't know where we came from, it will become
impossible to move forward!

> He also included a non-operational H89 that I'm trying to diagnose. It
> gives a single beep when powered up and i get raster and a blinking
> cursor but no prompt or keyboard response.

If you push the OFF-LINE key and type on the keyboard, do you see the
characters? If so, the TLB, keyboard, video board, and power supplies
are all working. That narrows the problem down to the CPU board.

If you don't get characters with OFF-LINE down, then there is a problem
on the TLB or keyboard. It may be as simple as the keyboard is unplugged.

--
Results! Why man, I have gotten a lot of results. I know several
thousand things that won't work. -- Thomas A. Edison
--
Lee A. Hart http://www.sunrise-ev.com/LeesEVs leea...@earthlink.net

[Glenn Roberts]

Well I made some progress… before the smoke started!  have never dealt with an ’89 before so I’m already learning…

 

I removed the three wire plug that serves as one of the power supplies to the CPU board on the H89 (red/black/orange, plugs into P516) and turned the unit on.  Miraculously the terminal side started to work.  I can go off line and type to my heart’s content; good solid display.  I measured the voltages on the power supply and found the +5 and +18 V as expected.  I then powered down, plugged the plug back in (essentially re-enabling the CPU board) and a few things happened.

 

There was communication between the terminal and cpu but it was garbled – it is as if the terminal and CPU weren’t set to the same baud rate?? (seems unlikely!)  Or maybe there’s a faulty connection??   The good news is this means both boards are at least coming alive, just that one or both are misbehaving.

 

At some point I saw smoke and immediately shut down.  I think it came from the black cylindrical piece on the CPU board in the center of the attached picture.  It’s a polarized device, is this a zener diode?  The part itself obscures the part number.  It seemed hot to the touch.

 

The tantalums (at least what I can see) all look OK.  Not sure how to test (when these fail they short out?)

 

Looking at the schematic I see there is a second source of power to the board.  So I probably need to test that power as well.  If there’s a step by step diagnostic process somewhere in the library let me know.

 

I see Les has the assembly instructions for the H88 including procedure for testing the power supply.  Maybe I’ll start there next…

 

-          Glenn

[Kenneth L. Owen]

Hi Glenn,

Yep, you DO HAVE a TANTRUM Capacitor!!

Attached is the scematic for the area in your picture and a list of H89-CAPS.PDF.

[Glenn Roberts]

Ah. A tubular cap?!   hadn’t seen that before.  I only know about the orange or blue ones.  I’ll keep digging. Thanks!

[Glenn]

how many of you have just gone in and replaced all the tantalum cap's in the '89?  From Ken's list it looks like there are 28?  sounds like a lot of work, on the other hand it sounds like i could fix one, get everything put back together, and then have another one blow...  any consensus on best practice here?  Is it worth the effort?  risks, difficulty with getting the old ones de-soldered?

 

- Glenn

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[Mark Garlanger]

The ones that seem to be the biggest issue, are the ones around the
power supply. There are 3 across the top of the CPU board. When one
went, I replaced those three. If you do those three, be careful, 1 has
the opposite parity than the other two. And you will get a nice pop if
you don't get it right ;-)

One of the comments that was given to me by some members of the group,
is that you don't have to replace it with a tantalum. If I remember
the logic correctly, the other types of capacitors have much better
tolerances than they did 30 years ago.

Mark

On 7/26/12, Glenn <glenn.f...@gmail.com> wrote:
> how many of you have just gone in and replaced *all* the tantalum cap's in

>> *From:* se...@googlegroups.com [mailto:se...@googlegroups.com] *On
>> Behalf Of *Kenneth L. Owen
>> *Sent:* Wednesday, July 25, 2012 7:10 AM
>> *To:* se...@googlegroups.com
>> *Subject:* Re: [sebhc] some new challenges

>> sebhc+un...@googlegroups.com.

>> For more options, visit https://groups.google.com/groups/opt_out.
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[Terry Gulczynski]

I used standard electrolytics - works fine.

>>> Well I made some progress� before the smoke started! have never dealt
>>> with an �89 before so I�m already learning�

>>>
>>>
>>>
>>> I removed the three wire plug that serves as one of the power supplies to
>>>
>>> the CPU board on the H89 (red/black/orange, plugs into P516) and turned
>>> the
>>> unit on. Miraculously the terminal side started to work. I can go off

>>> line and type to my heart�s content; good solid display. I measured the

>>> voltages on the power supply and found the +5 and +18 V as expected. I
>>> then powered down, plugged the plug back in (essentially re-enabling the
>>> CPU board) and a few things happened.
>>>
>>>
>>>

>>> There was communication between the terminal and cpu but it was garbled �
>>>
>>> it is as if the terminal and CPU weren�t set to the same baud rate??
>>> (seems
>>> unlikely!) Or maybe there�s a faulty connection?? The good news is this

>>>
>>> means both boards are at least coming alive, just that one or both are
>>> misbehaving.
>>>
>>>
>>>
>>> At some point I saw smoke and immediately shut down. I think it came from
>>>
>>> the black cylindrical piece on the CPU board in the center of the attached
>>>

>>> picture. It�s a polarized device, is this a zener diode? The part itself

>>>
>>> obscures the part number. It seemed hot to the touch.
>>>
>>>
>>>
>>> The tantalums (at least what I can see) all look OK. Not sure how to test
>>>
>>> (when these fail they short out?)
>>>
>>>
>>>
>>> Looking at the schematic I see there is a second source of power to the

>>> board. So I probably need to test that power as well. If there�s a step

>>>
>>> by step diagnostic process somewhere in the library let me know.
>>>
>>>
>>>
>>> I see Les has the assembly instructions for the H88 including procedure

>>> for testing the power supply. Maybe I�ll start there next�

[Lee Hart]

On 7/26/2012 11:06 AM, Glenn wrote:
> how many of you have just gone in and replaced _all_ the tantalum cap's

> in the '89? From Ken's list it looks like there are 28? sounds like a
> lot of work, on the other hand it sounds like i could fix one, get
> everything put back together, and then have another one blow... any
> consensus on best practice here? Is it worth the effort? risks,
> difficulty with getting the old ones de-soldered?

I've never replaced them all in an H89. I usually replace the ones that
blow; it's pretty obvious!

But I have replaced them all in other equipment. I had an S-100 computer
that used a dozen or so of them. After a few *bangs*, I gave up and
replaced them all.

--
Ring the bells that still can ring
Forget your perfect offering
There is a crack in everything
That's how the light gets in.
-- Leonard Cohen, from "Anthem"

[Lee Hart]

On 7/26/2012 11:18 AM, Mark Garlanger wrote:
> The ones that seem to be the biggest issue, are the ones around the
> power supply.

This is because when a tantalum capacitor fails, it typically fails
*shorted*. This shorts the power supply, causing a huge current. The
capacitor can't handle amps, and it *explodes*!

Tantalums in parts of the circuit where they can't get a high current if
they short will just silently fail shorted. For example, the little
TO-92 regulators on the CPU board can only deliver about 0.5 amps into a
short. That's not enough to make a shorted tantalum blow. So it silently
sits there shorted, and the regulator runs flaming hot.

> One of the comments that was given to me by some members of the group,
> is that you don't have to replace it with a tantalum. If I remember
> the logic correctly, the other types of capacitors have much better
> tolerances than they did 30 years ago.

Tantalums still have better performance than aluminum electrolytics.
They have about 10:1 lower ESR (equivalent series resistance), and
filter well to at least 10 times higher frequencies. An electrolytic
needs to have at least 10 times the capacitance (and so is 10 times
bigger) to do the same job.

However, aluminum electrolytics typically fail *open* instead of
shorted. :-)

--
Don't worry about people stealing your ideas. If your ideas are any
good, you'll have to ram them down people's throats. -- Howard Aiken

[Lee Hart]

On 7/26/2012 11:27 AM, Terry Gulczynski wrote:
> I used standard electrolytics - works fine.

Standard electrolytics will still work; just not as well. The ripple and
noise will be higher, but that doesn't really matter much in digital
applications like this.

It might matter to the AM radio you have sitting next to the computer,
though! :-)
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exup�ry

[Kenneth L. Owen]

Hi Glenn,

I generally replace the ones that have failed (duh!) but don't change the ones still working OK unless it is a bad place to get into and I don't want to go back.

-- ken

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[Dave McGuire]

On 07/26/2012 12:47 PM, Lee Hart wrote:
> Tantalums still have better performance than aluminum electrolytics.
> They have about 10:1 lower ESR (equivalent series resistance), and
> filter well to at least 10 times higher frequencies. An electrolytic
> needs to have at least 10 times the capacitance (and so is 10 times
> bigger) to do the same job.

They do. There are some interesting newer technologies, though, that
you might want to look at if you haven't already. My local friend Dan
turned me on to these a few months ago when I had a really stringent
capacitor requirement (ESR and physical size) in a new design for work.

I've started using "aluminum organic polymer" capacitors. The ones
I'm using are Nichicon "CG" series. 2700uF @ 6.3V in a 10mm x 12.7mm
can, with an ESR of 12 milliohms and a rated ripple current of 5.1A.
Their innards are solid, not liquid, so they don't boil and burst, hence
they are non-vented...no "K" scores on the top. These are really,
really nice capacitors. These are less than $2/ea in qty. 1.

My new controller design has just gone into volume production
(woohoo!) with these capacitors.

Materials science is giving us some great new stuff to work with lately!

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

[Jack Rubin]

Very nice - I've found chip form factor and radial cans. Have you found (or
decoded) an axial version?
Jack

[mcg...@neurotica.com]

Unfortunately not. I work exclusively in surface-mount, except when through-hole absolutely cannot be avoided.

One should be able to rig one of these packages in a radial through-hole site at least, though. They have flat pins coming from the bottom of the cans; they effectively become radial through-hole parts when those leads are bent out.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

[Chris Elmquist]

Don't forget about the tants on the floppy drive PCB too. Those fail
with a spectacular "Mission Impossible" like scene with a puff of smoke
billowing out of the drive door-- Something is self-destructing :-)

This is probably getting old now but I always warn about that darn AC
line filter in the H89 too. They used one in a plastic enclosure and
when the caps in it fail, the whole thing lights on fire. Since that
line filter is live any time the cord of the '89 is plugged in the wall,
no matter whether the power switch is on or not, this could be a fire
hazard if you are not around when it decides to rapidly disassemble.
Therefore, until you replace the line filter, best not to leave the H89
plugged in and unattended.

Chris

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[Kenneth L. Owen]

Glenn,

I have a replacement line filter if you need one.

-- ken

[Glenn Roberts]

Following Ken's advice I found the bad tant on the CPU board and when I
remove it the system works!!, BUT only if the drive is unplugged from the
controller board, so it sounds like I'll be pulling the floppy drive to look
for the one that "self destructed in 5 seconds..."

- glenn

-----Original Message-----
From: se...@googlegroups.com [mailto:se...@googlegroups.com] On Behalf Of

[Kenneth L. Owen]

Hi Glenn,

Before troubleshooting the floppy drive, substitute a known good drive to see if it does the same thing.  If so, the problem is probably on the CPU card.

-- ken

[Glenn Roberts]

Ok

 

 

From: se...@googlegroups.com [mailto:se...@googlegroups.com] On Behalf Of Kenneth L. Owen
Sent: Friday, August 10, 2012 8:39 PM
To: se...@googlegroups.com
Subject: RE: [sebhc] some new challenges

 

Hi Glenn,

[Glenn Roberts]

I had only a few minutes to play with it last night.  Substituted one of my original H-17 drives; jumpers were set the same way as the one I removed (drive 0 I presume, though I’ll need to verify that).  Powered up; double beep and H: prompt.  I presume you type “b” and then 0 to boot from the drive? (sorry, H89 newbie). Nothing happened (but at least the system ran!).  I’ll have to look at the old drive I pulled out for problems…

 

From: se...@googlegroups.com [mailto:se...@googlegroups.com] On Behalf Of Kenneth L. Owen
Sent: Friday, August 10, 2012 8:39 PM
To: se...@googlegroups.com
Subject: RE: [sebhc] some new challenges

 

Hi Glenn,

[SKWebb]

Hi Glenn,

You said you were an H89 newbie, so for what it's worth, you should press the space bar a few times if the boot seems to hang. The boot code wants to determine baud rate between the Terminal and CPU boards. If the boot disk is newly inited or has been write protected all the time like a distribution disk this problem can arise. Once the baud rate has been determined, the boot code tries to write it back to the diskette, so you won't need to do this again.

~ Stanley

On Saturday, August 11, 2012 5:08:20 AM UTC-6, Glenn wrote:

I had only a few minutes to play with it last night.  Substituted one of my original H-17 drives; jumpers were set the same way as the one I removed (drive 0 I presume, though I’ll need to verify that).  Powered up; double beep and H: prompt.  I presume you type “b” and then 0 to boot from the drive? (sorry, H89 newbie). Nothing happened (but at least the system ran!).  I’ll have to look at the old drive I pulled out for problems…

 

From: se...@googlegroups.com [mailto:se...@googlegroups.com] On Behalf Of Kenneth L. Owen
Sent: Friday, August 10, 2012 8:39 PM
To: se...@googlegroups.com
Subject: RE: [sebhc] some new challenges

 

Hi Glenn,

Before troubleshooting the floppy drive, substitute a known good drive to see if it does the same thing.  If so, the problem is probably on the CPU card.

-- ken


On Fri, 2012-08-10 at 20:37 -0400, Glenn Roberts wrote:

Following Ken's advice I found the bad tant on the CPU board and when I

remove it the system works!!, BUT only if the drive is unplugged from the

controller board, so it sounds like I'll be pulling the floppy drive to look

for the one that "self destructed in 5 seconds..."

- glenn

-----Original Message-----

[Mark Garlanger]

Glenn,

   Even though the jumpers appear the same, you can try B(oot) 1, and B(oot) 2, just to make sure of the drive ID. Also, unit 0 is implied, so B(oot) is the same as B(oot) 0.

Mark

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[Glenn Roberts]

Yep got it.  That's the same as the h8.  Haven't gotten that far yet.  Thanks!

Sent from my iPad

To view this discussion on the web visit https://groups.google.com/d/msg/sebhc/-/QdTdmCkOXegJ.

[Glenn Roberts]

Well I go the old H89 to boot!  I consulted the manual and it says the disk controller needs to be in P506/P512?  Anyway I had it in a different slot but when I moved it I was able to boot from one of my H17 drives (the drive that came with the ’89 is having some problems; won’t boot).  So it’s limping to life.  Now I need to permanently replace that bad Tant Cap and then do some more testing.  Thanks all.

 

-          Glenn

[Mark Garlanger]

Due to the shortage of pins in the H89 (compared to the H8), not all address lines are routed to the slots, so each slot has an implied value for some of the address lines. If the hard-sectored controller is not in the right most slot, it will not have the right address.

Mark