Re: power supplies, was Re: NetBSD/vax

[Dave McGuire <mcguire%neurotica.com@localhost>]

On 3/22/20 4:37 PM, sadness wrote:
>>> I was also able to repair the m76 psu so I will do some testing on that
>>> system too, it will probably happen in the next few days or maybe the
>>> next few hours if I'm forced to lock down my shop.
>>
>>   Out of curiosity, what was the failure mode of that power supply?
> 
> In my power supply the problem was caused by failed capacitor, there was
> four nichicon 1800uf 25v caps that has leaked all over the board and
> corroded some of the solder joint in the pcb, every other caps in the
> psu was fine except this four, replaced them, cleaned the pcb, redone
> the damaged solder joint and the power supply is now working as is
> should, before the repair it was totaly dead, no voltage on any rail, no
> power led, not even the classic ticking sound of a switching psu in trouble.

  Nice recovery.  Thanks for the info.  We have a number of machines
that use the H7821 power supply in storage at LSSM.  We've begun
construction of a new exhibit floor on which some of these machines will
be shown off, so I've made a note of your PSU's failure mode to keep
handy when we start digging into those machines.

  That is, if we ever get out of COVID19 lockdown.  Sigh.

                -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA