Troubleshooting HP 2116B

[David Collins]

Christian, I tried to track down details of the 1820-0183 and the manuals
appear to say it's an RCA item, part number 80170 but I cant find anything
with that number anywhere - you are probably on the right track with a
CA3082A or similar.  

My experience in fixing similar faults on the memory boards of the 2116A was
that the transistors were often leaky which created stuck bits.  Sometimes I
had to swap parts around between working and non-working bits to isolate the
faulty items and it turned out exact replacements for the bad transistors
were still available for purchase. 

If you're prepared to swap components around on your boards to troubleshoot,
you might by lucky and find that the ICs are OK.  

David Collins

-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Christian Corti
via cctalk
Sent: Friday, 27 July 2018 9:14 PM
To: cctalk at classiccmp.org
Subject: Troubleshooting HP 2116B

Ok, so I've got the computer almost running now. I now need to fix both
sense amplifier cards. One (0..4k) sometimes reads a one for bit 3 after the
machine has warmed up. The other (4..8k) has a stuck one for bit 7.
Swapping these cards make the errors move to the other core bank
respectively.

I have the newer cards, 02116-6298, not the older 02115-6001 The latter has
CA3028A used as sense amplifiers. My card uses HP
1820-0183 (metal can IC from RCA). I guess that it is also a CA3028A or
maybe a CA3053. Can anyone confirm this?

Next, the manual on bitsavers (02116-9153_2116B_Vol2_Oct70, and the same as
found on the hpmuseum site) not only contains some errors (see my other post
about the front panel lamps). It has also some badly scanned pages with
parts missing, notably page 5-50 (PDF page 350) lacks the right part of the
page. Is there a better scan available? My 1968 copy does not list the
02116-6298.

Christian