HP-97S BCD POD

[ignazio]

Hi,
who can help me to restore a bad BCD pod? It has the control PCB bad. There is a repair protocol to find the bad components?
Thanks for your contribute.

[Katie Wasserman]

(05-17-2014 08:37 AM)ignazio Wrote:  Hi,
who can help me to restore a bad BCD pod? It has the control PCB bad. There is a repair protocol to find the bad components?
Thanks for your contribute.

Almost all of the IC's in the pod 4000 series CMOS or 74C series and are still readily available and very cheap. I helped my friend repair his without having a schematic by doing the following simple technique:

1) Swap the main 24 count IC board with a known good pod to determine which of the two boards had the problem. (It sounds like you already did this step.)

2) On the bad board, de-solder (with a nice de-soldering tool) each IC and test it with a IC tester (look around the internet, almost any one will do 4000 series and 7400 series chips and they can be bought for $40US or so).

3) Replace the IC's that don't identify on the tester. We found a bad 4043 chip, we knew this one becasue it was labeled MC14043B. But the HP part numbers on this board are easy to find in cross-reference lists.

On the main 24 count IC board only the one labeled 1818-0565-1 is not a standard IC, I think it's a ROM.

Of course the "better" way to do this is to get a hold of Tony Duell's schematic and debug it with a logic probe. But I think that that could take considerably more time as this is a complicated circuit with much of it only functioning based on the BCD input you'll need to provide.

[ignazio]

Hi Katie,
Thanks for your advices, I'm awaiting for a IC tester purchased today.
Regards from Italy.