[HECnet] No connectivity to arsgea 4

[Johnny Billquist]

...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