[HECnet] No connectivity to arsgea 4

[Peter Lothberg]

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:
>>> 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
>>>>>>
>>>>>
>>>>
>>>>
>>>
>> 
> 
> --
> 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