----- Original Message -----
From: Dwight Elvey <elvey_at_hal.com>
To: <classiccmp_at_classiccmp.org>
Sent: Tuesday, April 25, 2000 10:10 PM
Subject: Re: PDP-5 Rescued!
> Chuck McManis <cmcmanis_at_mcmanis.com> wrote:
> > This didn't seem to make it out the first time, so here goes a second.
> >
> > I managed to rescue the PDP-5 that I've "owned" for some time now, but it
> > was stuck in a far away city. Anyhoo, I've put up the obligatory pictures
> > at <http://www.mcmanis.com/chuck/computers/pdp5.html> for anyone who cares
> > to take a peek at it. This uses "DEC System Modules" the pre-cursor to the
> > DEC Flip Chip technology. It hasn't been powered on in 15 years so I'll be
> > a bit cautious getting the caps warmed up in the PSU. -15V transistor
> > logic, wild stuff!
> >
> > --Chuck
>
> Hi Chuck
> If I was worried about the capacitors, I'd disconnect them and
> use a bench supply with a nice current limiting resistor. I
> would think a step rate of 5% of working voltage every 1/2
> hour would be safe. Put a volt meter across the resistor.
> Any significant large voltage drop would indicate leakage.
> These large caps are known to have some leakage. How much
> is OK, I don't know. That is something you'll have to make
> a judgment call on. I would think that for large caps like
> I see in the pictures, 1/32 watt is on the large size for
> DC power.
>
Even if they turn out to be a bit leaky keep them under a moderate
voltage and they may repair themself. The electrolyte will react with
the bare aluminium and reform an oxide dielecticum that will fix
things. Gradually increase the voltage to the nominal voltage of the elco
minus 10%.
I've even seen valve-tube guys put a short burst of very high voltage
on a defect elco to fix them but that was with the real liquid type elco
ps: don't ever try this with tantalium type elco's, You'll propably have
to scratch them from your face!
Sipke
Received on Tue Apr 25 2000 - 18:19:33 BST