22 Jan
2021
22 Jan
'21
7:03 p.m.
The KA has no switching power supplies.....
-P
----- Original Message -----
From: "bqt" <bqt at softjar.se>
To: "hecnet" <hecnet at Update.UU.SE>
Sent: Friday, January 22, 2021 12:43:40 PM
Subject: Re: [HECnet] No connectivity to arsgea 4
...despite Peter's experience with a KA10. I
can't really comment on the
PDP-10s, since I've never worked much on them. But since I suspect they
might not have had switched power supplies, I'm not surprised if it
worked just fine, even after longer storage.
The only 10s I have worked a bit more on is KL10. And replacing a power
supply for the MF10 was quite a job, since it was a linear supply with a
big trafo in it. *Very* heavy... :-)
Johnny
On 2021-01-22 18:39, Johnny Billquist wrote:
And speaking of power - the one thing that I have
experienced a lot on
11/70 machines are the H7440 regulators. They tend to blow up. And
especially if just kept in storage for longer periods, and then starting
to be used again...
Don't leave these machines off. That's all I say. That's when you get
trouble.
? Johnny
On 2021-01-22 18:36, Johnny Billquist wrote:
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol Not really trying to claim there is anything
particular about DEC
equipment here. While they were built properly, I don't think there
necessarily is anything exceptional about them.
But no, I do not believe any components have been replaced. One of the
biggest issue is when equipment are left turned off for longer times.
That usually seems to be the time when problems appear. These machines
are (or were) running 24/7, and have always done so. There might have
been one or another card replaced from time to time, since they were
on service contracts for a long time. But just by looking into them,
if something had been replaced, it was a long time ago. Based just on
the general look of the cards.
By the way, we're talking 11/23 machines here. So BA23 box. Not that
much loaded in them, so no big strain on the power supply.
My experience with 11/70 machines are the same. If they are kept
running, they usually just continue to work. If you have them off for
a couple of years, you'll have a lot of work before they are stable
again.
But disk drives get into trouble with age, even if continually
running. And some are worse than others. The RD53 is sortof infamous
here...
?? Johnny
On 2021-01-22 18:15, Dave McGuire wrote:
?? 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:
>> 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
>>
>