6 Sep
2014
6 Sep
'14
8:31 a.m.
Can I hijack this thread for another IC quality related question?
I'm in the early stages of trying to restore a ROLM CBX 8000 and I'm
finding that on certain cards; mostly 8550 shelf expanders and 8551
16-channel coders; there are noticeable amounts of TI 7400 series logic
produced in the following facilities:
EL SALVADOR
MALAYSIA
TAIWAN
where the IC leads have experienced, in my opinion, "excessive corrosion".
Date of manufacture on these parts ranges from mid-1970s to early 1980s.
ICs in the switch produced by other vendors e.g. AMD, Mostek, Zilog, Intel,
Rockwell, GI, Signetics, Motorola, OKI, etc as well as passive components
don't seem to really have this problem; leads are free of corrosion; it's
really just 7400 series "little logic" from TI on these two card types,
where the corrosion is occurring.
Has anyone ever seen this sort of thing before? Before I got the unit,
AFAIK, it was stored in a nominally dry-and-out-of-the-elements but not
really climate-controlled storage locker for probably at least a decade or
so. I've had other bits of equipment spend some time (years) in lockers and
never seen any internal corrosion... the corrosion on 8550 and 8551 cards
occurs across all six shelves of the PBX from top to bottom so it doesn't
appear that, say, one part of the PBX was any more exposed to the elements,
corrosive atmosphere, etc.
No meaningful corrosion on the PBX frame, card shelves, terminal strips,
connectors, fuse panel, ... any other metal component, really.
Was TI cheaping out on the metal used for package leads for a little while
there, or ...?
Best,
Sean
On Sat, Sep 6, 2014 at 10:18 AM, Dave Caroline <dave.thearchivist at gmail.com>
wrote:
There was a problem with some plastics used in the
early days, it was
mentioned in the press at the time (EDN etc), I dont remember it being
company specific
Dave Caroline
On 06/09/2014, Mattis Lind <mattislind at gmail.com> wrote:
After the successful restore of the HP9830B I
continued with the HP9810A
that I was able to get from the Swedish Maritime Administration. (
http://www.datormuseum.se/computers/hewlett-packard/hp9810a )
The machine has been sitting in a storage container for many years until
I
was able to rescue it. And of course it was dead.
Testing the CPU boards
in
the working 9830 gave that three out of four
boards were faulty.
This far I have replaced four TTL chips. Three on the clock board and one
on the ALU board and all of them are made by National Semiconductor, date
codes are mid 1972. All are plastic DIP. The failure mode seems to be
that
the outputs are floating. I guess that the
bonding wires are broken.
Can it be that the moisture in the storage container that has made it
into
the chips corroding the wires?
What is the experience when it comes to different manufacturer and
plastic
DIP TTL? Which are better, which are worse after
40 years?