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

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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:



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