VAX 4000-500 PSU Overload?

Holm Tiffe holm at
Mon Dec 14 04:53:23 CST 2015

Robert Jarratt wrote:

> > -----Original Message-----
> > From: cctalk [mailto:cctalk-bounces at] On Behalf Of Glen Slick
> > Sent: 14 December 2015 01:36
> > To: General Discussion: On-Topic and Off-Topic Posts
> > Subject: Re: VAX 4000-500 PSU Overload?
> > 
> > I took a look at the DSSI & SCSI termination power supply board in my VAX
> > 4000 BA440 chassis. It's the small board in the storage area of the backplane
> > mounted in place by a single screw. There are two identical circuits based on
> > the LT-1086 with the adjustable output voltage set at 5.30V  [1.25V * (1 +
> > 392/121)]. Each circuit has a 100uF 35V 105C nichicon cap between the input
> > and ground and the output and ground. Both circuits on my board still output
> > 5.3V from a 12V input, but I think the caps are starting to leak electrolyte on
> > the PCB and I should replace them all (4 total) before things get ugly.
> >
> I just got the board out. The caps on mine look OK, but I see the ESR is at or just above the value suggested on the table printed on my meter. So I will replace them all.

All of the Nichicons in my PSU and that Terminator Power Source looked ok,
but that was all...totally dead from the ESR side of view.

Don't bother with what you measure, replace them all if you can.

The leaking Caps in my PSU where from another Manufacturer (don't remember
wich one) and had a black color.


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