|Re: HP-97S with a bad BCD interface: help me!|
Message #2 Posted by Katie Wasserman on 21 Mar 2011, 8:10 p.m.,
in response to message #1 by Ignazio Cara (Italy)
The pod for the 97S has 50 or so 4000 series CMOS chips in it, it's possible one or more of them are bad -- I've seen this happen in one case in particular All of these chips except one ROM are still readily available for purchase and they are very inexpensive.
The 97S manual has a partial schematic of the pod which will help in debugging, but in working with a friend of mine we decided to pull all the chips (i.e., de-solder them) and test them in a handi-dandy IC tester I have. We were able to find the bad chips and replace them pretty easily.
You can find some of the 4000 series part numbers cross referenced to the HP part number here.
Better still, here's an almost complete cross reference list of the IC's used in the 97S pod from my notes:
MC14043B 4043 (obviously)
MC14512 4512 (obviously)
If you want to debug by tracing signals you should get a hold of Tony Duell's hand drawn schematics for the 97s pod, that will help a lot.
Edited: 21 Mar 2011, 8:34 p.m.