Memory Voltage on MicroVAX II

Robert Jarratt robert.jarratt at
Sat Dec 5 12:29:04 CST 2015

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Jon Elson
> Sent: 05 December 2015 18:03
> To: General at; Discussion at and Off-
> Topic Posts
> Subject: Re: Memory Voltage on MicroVAX II
> On 12/05/2015 09:51 AM, Robert Jarratt wrote:
> > I finally fixed my H7864 PSU so I can now run my rtVAX 1000. However,
> > I think the machine is damaging memory boards. I checked the ripple
> > and 5V looks OK, but 12V looks suspicious. Is the 12V supply used by the
> memory?
> I don't have my print set anymore, but I highly doubt it.  I think the +/-
12 V is
> only used by serial comm boards, and possibly by some graphics boards.  I
> would not be surprised if the regulation of the 12 V supplies is not very
> precise.
> Jon

There seems to be a spike on the 12V supply, surely that isn't good, even if
it doesn't affect the memory?



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