[Info-vax] VAXStation 3100

[Chris]

On 01/16/19 20:41, Bill Gunshannon wrote:
>
> OK, before I go screwing with it any more than I need too....
>
> I fired up the first 3100. It has 7.1 (but I don't remember
> any of the passwords. Not a problem, I know how to break into
> the box and reset the system password.) and 5.5 on it. That
> must go back quite a ways.
>
> But here's the new problem. I plugged an Expansion box in
> the same outlet strip and connected them together. Kicks
> the GFCI breaker!! Disconnect the SCSI between the two
> boxes. As soon as I turn the second one on it kicks the
> GFCI. Either one is OK by itself, but the two together
> kicks the GFCI. Other than a wiring problem in the power
> supply (I assume it would take one of them having the white
> and black wires reversed in side the box) what else could
> cause them to kick a GFCI as opposed to a circuit breaker?
>
> bill
>

If that's a ground fault detector, remember that switch
mode power supplies hav a lot of ground leakage current,
because of the filter caps. With caps in good condition,
that current should be balanced and not trip the breaker.

However, many psus from that period used RIFA caps in
the filters, the scourge of restorers of systems
and test gear worldover :-). The expoxy case splits with
age, damp gets in and they can go bang, or fill the case
with smoke and cover all surrounding parts with a black
tar like substance.

I would not power up again until the psu covers and added
caps around the power unlts have been checked. I usually
just cut or unsolder all RIFA brand caps, replace if you
want to with polypropylene types, or just leave them out.
Not much effect in tersm of rfi anyway, only to satisfy
fcc regs. About an hours work, but well worthwhile...

Chris