22 Jan
2021
22 Jan
'21
6:31 p.m.
The KA10 built in 1966 had ONE broken memory chip (in the fast AC) after
being in storage for 30Y and traveled by sea across half of the world....
(and some bad contacts on two cards that had to be cleaned...)
-P
----- Original Message -----
From: "Dave McGuire" <mcguire at
neurotica.com>
To: "hecnet" <hecnet at Update.UU.SE>
Sent: Friday, January 22, 2021 12:15:20 PM
Subject: Re: [HECnet] No connectivity to arsgea 4
Sigh, yes, we all know of exceptions. But even then,
I doubt it can
be proven that those PDP-11 systems in production since the early 80s
have never had components replaced.
Not everything is built to DEC standards. That said, all my life
I've been replacing chips, diodes, transistors, capacitors, and
sometimes even resistors in DEC gear. It does happen, and it's not
uncommon.
The regulator bricks in the H742/H7420 power supplies tend to blow
Zener diodes. That's fresh in my mind because we just lost another one
at the museum recently. Those are failing with such frequency now that
I've purchased stocks of the components that tend to fail. (we have a
lot of those at the museum) And those ARE built to DEC standards.
Speaking of not being built to DEC standards, I've got a Heathkit H8
on the bench right now, I'm repairing it for a new exhibit at the
museum. Four failed (non-moving!) ICs replaced so far, it's very nearly
done.
-Dave
On 1/22/21 12:03 PM, Johnny Billquist wrote:
Well, I know of PDP-11 systems out in production
who have been running
since the early 80s. The only thing that fails is the damn RD53...
Replaced those about 20 years ago now. The rest of the machine was
running just fine. At that at a steel mill, so not exactly a friendly
environment. Last I heard, things were still running, but it might have
been replaced by now. But anyway, it's the moving parts that cause
problems. The rest usually just keep running...
? Johnny
On 2021-01-22 17:53, Dave McGuire wrote:
--
Dave McGuire, AK4HZ
New Kensington, PA On 1/22/21 11:41 AM, Thomas DeBellis wrote:
10 years used to be nearly unheard of for retail
machines with moving
parts.? When nothing is moving, then supposedly there is nothing to
burn out.
?? I don't know who told you that, but he/she knows jack point squat
about electronics.
?? Materials migration and diffusion across junctions causes
semiconductor components to fail, tin whiskers cause shorts, some
types of capacitors dry out and/or have their electrolyte deteriorate
or crystallize, resistors drift, heat/cool cycles cause PCB flexure
resulting in cracked solder joints, corrosion in air creeps into
connector pin interfaces and forces pins apart, the list goes on and
on and on.
?? To be fair, some of the above-listed failure modes do in fact
involve things moving, though imperceptibly so, my point stands.
?????????????? -Dave