Reparing Classics (was Re: PDP-11/44 Boot Prompt)

From: Ethan Dicks <erd_at_infinet.com>
Date: Mon Nov 2 10:38:24 1998

>
> At 07:13 PM 11/1/98 -0600, Doug Yowza wrote:
> >
> >In order to reach god status in our little domain here, you must be able
> >to repair anything that can go wrong with your machine using any resources
> >that might be available.

I don't know about being a God, but I do try to collect stuff I can
fix myself. I'm good with TTL logic (PDP-8/L, etc.) and can do surface
mount repair, but my theoretical knowledge of switchers is thin, as
is my ability to repair a CRT with no schematics. Fortunately, a
good friend of mine live three blocks away and he *can* fix CRTs with
no schematics.
 
> No kidding. Although I too hold the greatest admiration for someone
> who has the talent to do that, we must keep in mind that while
> our definition for "classic computer" is moveable and extends
> back ten years (now to November 1988) the time period for
> "repairable by human" probably ends at a specific fixed date,
> perhaps dooming some classic computer collectors to a certain
> time period, based on what they're willing and able to repair.

Able being the key word. Highly integrated stuff is not easy to find
spare parts for, neither are most monitors. I have a Commodore 1950
multisyunc monitor (barely 10 years old). It broke a few years ago.
I happen to have the service manual for it. The flyback was *never*
imported into the U.S. Commodore's policy was to not stock HV components
because that might constitute a policy of permitting repairs, subjecting
them to liability if somone got hurt or died while repairing the monitor.

-ethan

ObCoolRepairHack - It used to be tedious to diagnose and repair DEC M-series
FLIPCHIP modules. After I got a TTL/CMOS IC tester, I rigged up a cable
from a DIP test clip, some ribbon cable and a DIP header. Now, I plug the
cable into the IC tester, clip the diagnostic clip on a chip on the M module,
then press "TEST". The battery in the tester has to drive three to four
7400-series ICs, but the tests are valid. I should mention that this is
a bench test, not an in-place test. The I/O leads on the module just go
back and forth to the chip on most modules (the M220 and other dual-height
modules are an exception, of course).

Diagnosing a PDP-8/i is no longer a nightmare - just follow the prints,
make a few educated guesses, test two or three boards and (drawing from
a pile of TESTED spares), back in business.

-ethan
Received on Mon Nov 02 1998 - 10:38:24 GMT