H-8 one remaining bug to resolve - multiple tone when starting cold

[Mike Cassidy]

When I do a cold start of my H-8 I get multiple tones (versus just one when it has been turned on for awhile).  The multiple tones last only a couple of seconds then in settles in and everything is normal.  Guessing heat related and probably a cold solder joint but nothing obvious so far.  I have narrowed this down to one of my two installed H8-1 memory cards.  No issues when I remove it from the bus.   

I plan to start re-soldering but any thoughts on ways to troubleshoot this?

Thanks

[Randy E (OoMOR)]

How about when the suspect card is placed in a different slot? (to rule out cold solder joints at the backplane pins)

Are the pics/sockets at the backplane Tin, or Gold Plated? Have you tried cleaning the pins/sockets and using a little DeOxIt?

Randy

[Mike Cassidy]

Thanks Randy

I did move the memory card around to different slots.  No change.  Backplane Pins look to be tin.   I plan to DeOxit the sockets next.  

Regards,

Mike Cassidy

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[Randy E (OoMOR)]

Yeah, I figured you had already or were about to, but sometimes the obvious needs to be stated. (Oh Yeah! I forgot about that! syndrome)

Randy

[Tim R]

Mike, I may be headed down a rabbit hole with this story, but I too had sound issues on the H8.  In my case, the tone was more of a squawk than a beep, and I eventually tracked it down to IC103 on the front panel board. I hit the socket with DeOxit and reseated the chip which fixed my issue. I don't think you have the same issue, but I learned some things about how tones are generated via front panel IC103. That IC is a 14040 12-bit counter that is used to create a couple of different tones for the sound circuit based off the system clock. One of the interesting things is that sound circuitry also generates a beep when a system reset is detected on IC103, pin 11 (the 14040).  It sounds like you have two different devices/cards that are triggering a reset on system boot. 

I wonder if this would happen if both H8-1 cards are configured for the same memory address block, or one is jumpered for the 0K block? You have probably checked that already, but if not there are jumper links in the upper right side of the H8-1 card. If the two H8-1 memory cards are the only ones in the system, I think a proper configuration would be to set one with the 8K jumper in place, and the other with the 16K jumper in place.

None of this may apply to your issue, but hopefully is helpful,

Tim

On Wednesday, March 5, 2025 at 4:36:37 PM UTC-8 cmc...@gmail.com wrote:

[Glenn Roberts]

Also, when initially debugging a new system it’s best to start with as minimal a system as possible, so just a single 8k (or even 4K) board should be enough to bring up the monitor. Then you can use the memory test routine (in the H8 operations manual) to test the RAM boards…

Sent from my iPad

On Mar 6, 2025, at 9:32 PM, Tim R <t...@primal-bits.com> wrote:

Mike, I may be headed down a rabbit hole with this story, but I too had sound issues on the H8.  In my case, the tone was more of a squawk than a beep, and I eventually tracked it down to IC103 on the front panel board. I hit the socket with DeOxit and reseated the chip which fixed my issue. I don't think you have the same issue, but I learned some things about how tones are generated via front panel IC103. That IC is a 14040 12-bit counter that is used to create a couple of different tones for the sound circuit based off the system clock. One of the interesting things is that sound circuitry also generates a beep when a system reset is detected on IC103, pin 11 (the 14040).  It sounds like you have two different devices/cards that are triggering a reset on system boot. 

To view this discussion visit https://groups.google.com/d/msgid/sebhc/de2d2933-c0d4-48dc-bbb6-e08095274fban%40googlegroups.com.

[Mike Cassidy]

Thanks for this info Tim.  Interesting to know about the sound circuit.  I do believe that something on the suspect memory card is throwing system resets. But only for a few seconds until the something warms up.   The memory card that is causing the error is set for 16K.  Neither the 8K memory card or the installed H8-5 cause any issues.  I tried de-oxit on the socket as suggested by Randy (thanks) but no change.  I guess I'm going to be left with popping out the IC's and resoldering any suspect looking IC socket pins.  I note there are three tantalum caps on the board (C101, C102, C113) - I replaced a few of these on the processor board as they smoked when I started bringing the H8 back to life.  Maybe one of these is getting ready to go.    (I assembled the H8 back in the late 70's - played with it until PC's came along - been sitting in storage since then).

Thanks again for your insights.  Glad I found this group.  Miss the old Heathkit days.  

Mike

To view this discussion visit https://groups.google.com/d/msgid/sebhc/de2d2933-c0d4-48dc-bbb6-e08095274fban%40googlegroups.com.

--

Regards,

Mike Cassidy

[Glenn Roberts]

Great to see you restoring the same machine you built all those years ago!

Sent from my iPad

On Mar 7, 2025, at 4:45 PM, Mike Cassidy <cmc...@gmail.com> wrote:



To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAHs3Uu1WXRZO780HpcP%2BqTmsW%3DYWgxVTHs_xnd442NO2BbXA3g%40mail.gmail.com.

[Mike Cassidy]

Any recommendations on sourcing IC's?  Rochester has everything I'm looking for but $250 minimum order.  Seems like e-bay might be only way to go.

[Glenn Roberts]

I use Mouser and DigiKey, sometimes Jameco.

Are you looking for something unusual that the main vendors don’t stock?

Sent from my iPad

On Mar 9, 2025, at 6:50 PM, Mike Cassidy <cmc...@gmail.com> wrote:

Any recommendations on sourcing IC's?  Rochester has everything I'm looking for but $250 minimum order.  Seems like e-bay might be only way to go.

To view this discussion visit https://groups.google.com/d/msgid/sebhc/81cdec47-0931-47b8-9b85-f165508c7789n%40googlegroups.com.

[Mike Loewen]

Like Glenn, I get most of my parts from Mouser, then Digikey. For older
stuff, I occasionally use Anchor Electronics in CA, or Unicorn Electronics in
PA.

https://anchor-electronics.com/price-list.pdf

https://www.unicornelectronics.com/

Anchor is phone order only, but they're very friendly. Unicorn has a $30
minimum, but they often have old stock that no one else does.

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>
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Mike Loewen mlo...@cpumagic.scol.pa.us
Old Technology http://q7.neurotica.com/Oldtech/

[Mike Cassidy]

Delayed this project a bit but finally got back to it.  The bug was multiple system resets at power on but after warm up problem disappeared.  I had it narrowed down to one of the two H8-1 memory cards - the one jumpered for 16K.  After checking what looked to be cold solder joints I bought a few 4044' IC's figuring I'd just swap a few at a time to see what happens.  Sure enough, the last one I swapped was the problem.  But it wasn't the chip.  It was its contact with the socket.  Reseating it did the trick.   I would now like to run the Heathkit memory test routine.  In the test routine the size of memory gets loaded into memory address 040 105.  Supposed to use 057 for 4K or 077 for 8K.  This split octal stuff has me completely confused.   How do I figure out what contents to input for 16K?

Thanks

Mike  

[glenn.f...@gmail.com]

Congrat’s!

 

The RAM test in the book is set up such that it tests the same bank of RAM where the program itself resides so it has to avoid overwriting two things: 1) the test program itself and 2) the stack.  As listed in the manual (P. 61) it is set up to test a 4K RAM board starting at the 8K boundary.  Normally this would be 040.000 through 057.377 (or 0x2000 through 0x3000-1)… BUT… in order to avoid clobbering the program or the stack the start is set at 040.160 and the end at 057.260.

 

The good news is you have two RAM boards (I presume these have both been upgraded to a full 8K RAM each) so you can arrange things for a complete test of each board. The first thing to know is that when the H8 comes on the PAM-8 monitor searches (starting at 040.000) for the first 4K boundary where there is no RAM and sets the stack pointer to the top of continuous RAM (i.e. the top of the most recent 4K RAM bank.  So if you want to test an entire memory board you must leave a GAP between the two RAM boards so that the stack won’t end up being in the range of your test board.

 

So set the first one to start at the 8K boundary (i.e. 040.000) and set the second one somewhere higher. For example set the second board to start at 32K (200.000). Then you can set the start test address to 200.000 (i.e. put 000 200 at locations 040.101 and 040.102) and the end of the test range would be 237.377 (0xA000-1) so put 377 and 237 at locations 40.104 and 40.105 respectively.

 

I know split octal can be confusing. Hope this helps!

 

Let me know if you have any questions…

To view this discussion visit https://groups.google.com/d/msgid/sebhc/8fa7dd77-452f-48df-8266-984736b7014bn%40googlegroups.com.

[Glenn Roberts]

Just reread this…. So (duh) a simpler approach would be to just set the stack pointer yourself (via front panel or by adding the instructions at the start of the program) to something not in the range under test. 

Sent from my iPad

On May 3, 2025, at 3:40 PM, glenn.f...@gmail.com wrote:



[Joseph Travis]

If you have one, there is a memory test built into the H17 floppy disk controller board for the H8.  Enter in the following incantation to conjure it up:

REG PC ALTER 030003 ALTER REG BC GO GO

The left side display will increment from 000 to 377, displaying the current pattern being written / read from each address.  You should hear a beep if a failure is detected and the value is displayed.  Press REG DE to see the address of the failure.

Joe

To view this discussion visit https://groups.google.com/d/msgid/sebhc/F96BE025-C7E8-467D-A1A1-C8A67F429554%40gmail.com.

[Mike Cassidy]

Thanks Joe,  This is helpful info.  I never made the investment in the floppy disk accessory back in the day - IBM PC & clones got my attention.  But now thinking about acquiring an H17 controller card then getting a Semi Virtual Disk or something similar.  Any thoughts on that?   This Google Group is really helpful and inspiring me to get back with my H8 from a hobby perspective.

Thanks

Mike  

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAGQDgBA%3DwKUeGMQnv-ayF6%3Dyq%2Bd0ODOes0EPHjRDTKM6Xa_kMg%40mail.gmail.com.

--

Regards,

Mike Cassidy

[Joseph Travis]

'A few questions for you:
1.  What boards do you currently have?
2.  What are your ambitions for the H8 (hardware / software)?
3.  What OS' do you plan to use (CP/M, HDOS2, HDOS3)?
4.  What terminal are you using / plan to use?

Joe

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAHs3Uu3zrYO89Hx6MZeJ_eQ86cfk8ouV%3D65%2B-JeAoEnojYjyhQ%40mail.gmail.com.

[glenn.f...@gmail.com]

Great point joe! FYI by default the memory test in the H17 ROM tests everything from 040.100 to top of RAM minus 64 (040.000 to 040.077 is working storage for the front panel monitor so that’s excluded from the test range and the top 64 bytes are excluded since they’re the working stack space.)

 

Note that there’s a HLT instruction which pops you back to the front panel monitor where you can adjust the starting address (HL) and ending address (DE), then hit GO (key 4).

 

 

As joe says, this will only work if you have an H17 or a more modern monitor ROM that includes the H17 code (e.g. XCON-8).

 

Good capability to know about!

 

• Glenn

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[Mike Cassidy]

Thanks Joe,

My H8 includes the CPU board, two H8-1 memory boards with 8K each, and H8-5 Serial I/O.  It's operating fine now.  I recapped the power supply a year ago.   

In the beginning (1979) I originally had an H-9 terminal.  It has not survived the years.  Keeping an eye out for an H-19.  

My goal is simply to be able to run BASIC (maybe assembler) and just play around with it from a sentimental standpoint.    

At the time I ran the BASIC software from a cassette.  I want to figure out what to do about a disk as I move forward.  I've been looking through the sebhc group trying to figure out an approach.  Sounds like trying to find an operational H-17 maybe not worth the effort.  But that's where I am currently.  Long way to go.  Open to any and all advice.

Mike  

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAGQDgBCx%3DXcux68EpN-zZKkhaT8E7kOvZOCOK8grJ28Jbxfbpg%40mail.gmail.com.

--

Regards,

Mike Cassidy

[glenn.f...@gmail.com]

Mike: with what you’ve got you should be able to run BASIC and/or do some simple assembly work. Take a look at this REMarks article I wrote a while back:

REMarks Issue 5 - 24 January 2022.pdf

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAHs3Uu0ZxUJXX8S9_p6JLtGcBr7X%3DKb6GBV0M9jChdC6r%2BvP4g%40mail.gmail.com.

[norberto.collado koyado.com]

Sounds like trying to find an operational H-17 maybe not worth the effort. 

 

You can build out your own H17 board and use 3.5” floppy drives to boot HDOS2/HDOS3 and CP/M.

 

Link here: https://koyado.com/heathkit/New-H8-Website/h8-h17-vdip1-fsb.html

 

Norby

 

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAHs3Uu0ZxUJXX8S9_p6JLtGcBr7X%3DKb6GBV0M9jChdC6r%2BvP4g%40mail.gmail.com.

[norberto.collado koyado.com]

Better off to just build out the CF card controller to do the same.

 

 

https://koyado.com/heathkit/New-H8-Website/h8-dual-cf-controller.html

 

Norby

 

To view this discussion visit https://groups.google.com/d/msgid/sebhc/SA3PR01MB79189E6FFDA93B3D0649400DF78F2%40SA3PR01MB7918.prod.exchangelabs.com.

[Joseph Travis]

I'm betting that you have an 8080 CPU board since you have the H8-5.  There are many different CPU boards that have been produced, most of which are Z80 based but, the 8080 CPU board will serve you well.  One thing I did with my H8-5 board was to mount a USB-Serial board on top of the 8251 used for the tape interface to allow me to download tape based software from my PC.  It is much faster (9600 baud) and more reliable.

I also would recommend getting the H8 Dual CF board.  You would have to upgrade your monitor ROM to XCON8 which requires some simple mods to the CPU board.  You could use a 2732 for XCON8 or get the 28C256 adapter board which can hold up to 4 different monitor ROMs.  You would also have to get a HA8-8 (aka ORG 0 or equivalent) board to run CP/M and HDOS3.

Norberto's website has many offerings as does Les Bird's.  Checkout the SEBHC github page, there's lotsa stuff available.  And of course, feel free to ask questions.  There are many in the group willing to help.

Joe

To view this discussion visit https://groups.google.com/d/msgid/sebhc/SA3PR01MB7918A4C4F4D6AC945E9C3DA4F78F2%40SA3PR01MB7918.prod.exchangelabs.com.

[norberto.collado koyado.com]

The 8080A  64KB board has the build in ORG 0. I think I still have one board left that I need to build to check out the layout. The same for the 512KB board.

 

Link: https://koyado.com/heathkit/New-H8-Website/h8-8080a-64kb-board.html

 

Thanks,

Norberto

 

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAGQDgBCoAOitAPQWEKVvTtVD%3DpnqgH5Nvh1tRqQJuBKANrp%2Byg%40mail.gmail.com.

[glenn.f...@gmail.com]

If you mostly just want the nostalgia trip use your H8-5 and one of the techniques from the REMarks article or Joe’s technique to convert the H8-5 to download digital content. This would require very little investment.

 

If you want to go farther and run one of the disk-based operating systems you’ll need more RAM, typically at least 32K, though more is better. This means buying or building a RAM board, e.g.: https://koyado.com/Heathkit/H8_8080A_64K_RAm_Brd.html.  That board also contains the “Zero Org” logic that will let you run CP/M or HDOS3 and has battery-backed RAM.

 

As Joe and Norberto have mentioned, one way to run these operating systems is by installing a compact-flash-based hard drive emulator (see link in Norberto’s email).  There are pre-configured CF images with all the operating systems and sample programs loaded. Some of these programs require an H19 or a PC running an H19 emulator.

 

Depending on how far you want to go we also have ways to interface with USB Flash drives (for file copying, not booting an OS).

 

Perhaps get started by doing the H8-5 thing and playing with some of the old tape-based programs, then decide if you want to go further!...

 

• Glenn

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAGQDgBCoAOitAPQWEKVvTtVD%3DpnqgH5Nvh1tRqQJuBKANrp%2Byg%40mail.gmail.com.

[Mike Cassidy]

Glenn,

Thanks for posting the link to your REMarks article.  I think this is the way to go as a starter to get back into the hobby. The daughterboard approach seems pretty straight forward and your article goes into good detail.  Tracking down an H8-5-1 daughterboard will likely prove challenging.  My next short term step is finding a reasonably priced H19.  In parallel I'll be researching the daughterboard approach.

To everyone else that has been chiming in on my questions - thanks very much.  What a fantastic support group

Mike  

To view this discussion visit https://groups.google.com/d/msgid/sebhc/07c701dbbd2a%24dd969130%2498c3b390%24%40gmail.com.

--

Regards,

Mike Cassidy

[Glenn Roberts]

The “Astrorat” daughterboard would have to be ordered from a PCB fab. Pretty sure Dave has the gerber files available. Maybe Joe can share the details on his approach, which came out after I wrote the article. He piggybacks a SparkFun breakout board on top of the 8251 USART. Pretty simple.

I can perhaps help you with the H19. The challenge is always shipping. Contact me off list and we can discuss.

Sent from my iPad

On May 4, 2025, at 7:58 PM, Mike Cassidy <cmc...@gmail.com> wrote:



To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAHs3Uu25Ae%3DONd022QQqK0Vu9yUVbVYdTqP-riUmVW4QPiB2JA%40mail.gmail.com.

[Mike Cassidy]

Joe,

Can you tell me more about adding the USB-Serial board on top of the USART on the H8-5?  Appears that there used to be a board fabricated for this purpose but probably no longer available (H8-5-1 daughterboard).  Glenn mentioned that you use a SparkFun breakout board.    And yes - I have an early H8 with the 8080.  

Thanks

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAGQDgBCoAOitAPQWEKVvTtVD%3DpnqgH5Nvh1tRqQJuBKANrp%2Byg%40mail.gmail.com.

--

Regards,

Mike Cassidy

[glenn.f...@gmail.com]

Hopefully this is the latest. Once Joe’s online he can verify that:

 

H8-5 Serial-Tape IO - Google Drive

 

I used the Sparkfun USB-C Serial Basic breakout (SparkFun Serial Basic Breakout - CH340C and USB-C)

 

Rather than solder directly to the 8251 I created a little breadboard, which I ended up sending to Tim Rogers. He featured that in one of his H8 restoration videos:

 

The Heathkit H8 Computer - Part 4: Terminal I/O and Benton Harbor Basic

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAHs3Uu3ZxWeEfG5mcGZ50HKOnrpRwFK8ygqSZQi6C-Rcw16E1Q%40mail.gmail.com.

[Tim R]

This solution works really well. I’ve been intending to duplicate the board Glenn sent, and I have the parts to do so. I’ll be back to the shop at the end of the week, so Mike, if you are looking for a prefabricated solution, I may be able to help. I may also have a spare 8251 laying around if you want to rig up the piggy-back solution and preserve your original 8251.

Tim

[Joseph Travis]

H8-5 USB - Serial I/O Mod

NOTE: Ensure the FTDI solder pads (on bottom) are set to 5V (NOT 3.3V)

1. Use clear RTV silicone to attach the FTDI board to the 8251 USART
2. Bend out the following pins on the 8251: 3, 19, 23, 25
3. Connect a wire between TxC (9) and RxC (25) on the 8251
4. Insert a 6 pin header into the FTDI board
5. Make the following connections between the FTDI board header and 8251:

FTDI <---> 8251
 GND <---> GND (4)
 CTS <---> RTS (23)
 Vcc <---> N/C
 TXO <---> RxD (3)
 RXI <---> TxD (19)
 DTR <---> N/C

NOTE: Using an 8251A USART will require you to bend out pin 17 (CTS) and
connect it to pin 4 (GND).  This modification is required due to internal
differences between the 8251 vs. 8251A and the way the USART is being used
to control the tape recorder.  Without this modification, the H8-5 will be

unable to DUMP program(s) / data to tape.

To view this discussion visit https://groups.google.com/d/msgid/sebhc/76377104-6711-469e-a7da-34066563095dn%40googlegroups.com.

[Joseph Travis]

'Sorry, there was an omission in the photos regarding the baud rate jumpers.  SER TX and SER RX should be connected together going to 9600.  On my boards, the connection is made on the solder side of the board.

Joe

[Mike Cassidy]

Tim and Glenn,

Thanks for the tips.  I watched several of Tim video's.  Really well done.  I'm even more motivated now.    Tim's point about restoring an H8 system to its original configuration hit home.  Much of it is about nostalgia and what a computer like the H8 represented at the time.  

I have ordered the SparkFun Serial Basic Breakout board.  Should have it next week.  I've read over the wiring instructions from Joe.  Should make more sense once I get my hands on the breakout board.  

Tim, if you do wind up with a prefab piggy-back solution, I am interested. 

Mike  

Tim R t...@primal-bits.com via googlegroups.com	May 5, 2025, 9:14 PM (12 hours ago)
to SEBHC

This solution works really well. I’ve been intending to duplicate the board Glenn sent, and I have the parts to do so. I’ll be back to the shop at the end of the week, so Mike, if you are looking for a prefabricated solution, I may be able to help. I may also have a spare 8251 laying around if you want to rig up the piggy-back solution and preserve your original 8251.

Tim

On Monday, May 5, 2025 at 5:19:08 PM UTC-7 Glenn Roberts wrote:

Hopefully this is the latest. Once Joe’s online he can verify that:

 

H8-5 Serial-Tape IO - Google Drive

 

I used the Sparkfun USB-C Serial Basic breakout (SparkFun Serial Basic Breakout - CH340C and USB-C)

 

Rather than solder directly to the 8251 I created a little breadboard, which I ended up sending to Tim Rogers. He featured that in one of his H8 restoration videos:

On Mon, May 5, 2025 at 9:14 PM Tim R <t...@primal-bits.com> wrote:

To view this discussion visit https://groups.google.com/d/msgid/sebhc/76377104-6711-469e-a7da-34066563095dn%40googlegroups.com.

--

Regards,

Mike Cassidy

[norberto.collado koyado.com]

Also, you can use same original HW and just flip SW101 to interchange the Cassette port with the Console port, to send data via the serial port of the PC to the H8. This setup was design to read/write from the paper puncher/reader or any RS-232 serial port.

 

 

Norberto

To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAGQDgBALcMQc%3DPhMeem6wH7Pot1QWbeT4QNEVeK0ubbJ-THLow%40mail.gmail.com.

[Mark Garlanger]

The H10 paper tape is parallel, and uses the H-8-2 parallel board, but I think they had identical port addresses and programming, so the software was the same.

Mark

To view this discussion visit https://groups.google.com/d/msgid/sebhc/SA3PR01MB7918D1F9D396BC1159D1A66FF77BA%40SA3PR01MB7918.prod.exchangelabs.com.

[norberto.collado koyado.com]

I was referring the Teletype ASR 33 using the 20ma loop circuit on the H8-5 board.

Get Outlook for iOS

---

From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Mark Garlanger <garl...@gmail.com>
Sent: Wednesday, June 25, 2025 9:24:36 PM

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