VAX 4000 PSU (H7874) Schematics

Christian Corti cc at informatik.uni-stuttgart.de
Fri Jun 8 02:58:31 CDT 2018


On Thu, 7 Jun 2018, Aaron Jackson wrote:
> The VAX turns on and the status LED stays on F. The DC lamp does not
> illuminate on the PSU. 5V rail appears fine but there is nothing from
> the 12V rail. There were some *very* dodgy looking caps which I have
> replaced, and some *very* exploded MOSFETs, which I have also
> replaced.

If that's all that you replaced, no wonder it still doesn't work ;-)
Usually shorted power transistors in SMPSUs also break one or more fusable 
resistors, maybe some diodes, maybe the driver IC or transistors.
So if you have anything that "exploded" in the power supply, be sure there 
is more work to be invested that replacing the obious parts.

Christian


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