9 Nov
2007
9 Nov
'07
1:22 p.m.
Date: Fri, 9 Nov 2007 17:45:36 +1300
From: Ethan Dicks <ethan.dicks at usap.gov>
Subject: Re: Commodore PET
<snip>
I got a lot of miles out of that PET. I still have it
and it still
fires up (but I think I have an IEEE problem that may turn out to be
cruddy 40-pin sockets on the VLSI I/O chips).
<snip>
Those sockets were indeed a PITA, but another easy-to-overlook problem
I ran into with my 8050 disk drive is that if you happen to catch the tip of
one of the contacts in the female IEEE connector while plugging in the cable
you can easily push it into the connector and out the back, causing an
intermittent.
m
9 Nov
9 Nov
5:17 p.m.
On 09/11/2007 18:22, M H Stein wrote:
Another problem I recall was that it's easy to damage the 6820s in a
PET, by plugging some user-port devices into the IEEE port or vice versa
(I can't remember which was more likely to upset things). We used to
fix it by replacing the damaged 6520 with a Motorola 6821, which is a
pin-compatible replacement, but seemed in practice to be more robust.
--
Pete Peter Turnbull
Network Manager
University of York
From: Ethan Dicks <ethan.dicks at usap.gov>
I got a lot of
miles out of that PET. I still have it and it still
fires up (but I think I have an IEEE problem that may turn out to be
cruddy 40-pin sockets on the VLSI I/O chips).
<snip>
Those sockets were indeed a PITA, but another easy-to-overlook problem
I ran into with my 8050 disk drive is that if you happen to catch the tip of
one of the contacts in the female IEEE connector while plugging in the cable
you can easily push it into the connector and out the back, causing an
intermittent. 
5:52 p.m.
On Fri, Nov 09, 2007 at 10:17:44PM +0000, Pete Turnbull wrote:
Another problem I recall was that it's easy to
damage the 6820s in a
PET, by plugging some user-port devices into the IEEE port or vice versa
(I can't remember which was more likely to upset things).
Hmm... I think I've escaped that particular damage, myself, but it's
good to know about.
We used to
fix it by replacing the damaged 6520 with a Motorola 6821, which is a
pin-compatible replacement, but seemed in practice to be more robust.
Indeed. I have 6821s lying about, but few spare 6520s. While debugging
my IEEE problems, I did try that swap, but no improvement. My plan is
to replace the leaf-contact sockets with turned-pin sockets when I am in
front of that PET again.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 9-Nov-2007 at 22:50 Z
South Pole Station
PSC 468 Box 400 Temp -38.2 F (-39.0 C) Windchill -53.1 F (-47.3 C)
APO AP 96598 Wind 3.5 kts Grid 59 Barometer 693.7 mb (10116 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
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