M7195 SLU issue might actually be 12v rail

Ethan Dicks ethan.dicks at gmail.com
Sun Oct 1 11:37:08 CDT 2017


On Sat, Sep 30, 2017 at 6:33 PM, Aaron Jackson via cctalk
<cctalk at classiccmp.org> wrote:
> Hi all,
>
> Instead of jumping straight in and ordering an SLU, I decided to check
> the power supply voltages. My +12V rail appears to be only giving about
> +4.6V

That does not sound fine.

> This is an 11/23+ chassis and the power supply seems very large

What type of box?  BA23?  BA11-M?  BA11-N?  You said "11/23+" which
could easily be a BA23, but it's not a guarantee.

In particular I ask because I'm sifting through a pile of DEC Qbus
backplane and PSU assemblies for, I think, a BA11-M, and these have
two PSU modules, one that takes in mains and provides +5V for the
backplane, then a smaller board that taps two cables off the main PSU
and provides +12V and -12V.  Both of these bolt down to a common
mounting bracket and have to be removed as a pair then each unit can
be removed from that.  The other Qbus supplies I have worked with are
single-unit affairs.

Any sort of Hxxx number you can find would be most illuminating.

-ethan


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