VAX 11/750 power supply fault

[CRC]

On Thu, 29 Nov 2007 12:02:05 -0700, J Blaser  
<oldcpu2 at rogerwilco.org>wrote:

>  In fact, a
> couple of the PS PCBs went through the dishwasher to clean up the
> remains to 'rodent residue'.  On the whole, it seems that I got them
> back together properly!  ;)

If there are any potentiometers on the boards that you washed, you  
might want to ensure that the wipers are making contact. Generally,  
pots are installed after a board wash unless they are sealed. An open  
wiper will cause many of the symptoms you are describing.

An easy method is to measure the resistance across the pot and then  
the resistance from each leg to the wiper. The sum of the wiper to  
legs should equal the resistance across the pot.

If the wiper appears to be disconnected, mark its position and then  
rotate the wiper through its travel and then back to the mark. If  
this fails to restore contact or the wiper contact is intermittent,  
replace the pot - it's not worth the effort trying to save a failing  
potentiometer.

	CRC