Replacing MicroVAX II PSU With a Modern PSU

Jon Elson elson at
Wed Nov 25 11:09:57 CST 2015

On 11/25/2015 11:01 AM, Robert Jarratt wrote:
> My reading of the Qbus spec is that P OK and DC OK are 
> active high. That diagram tells me that both control 
> signals are driven the same way because the two circuits 
> are identical except for the timing caps. When the power 
> is OK the output of the inverters is low, so the 
> transistors are off, presumably allowing the signals to 
> float high. When the power is not OK, the inverters are 
> high, turning on the transistors and shorting the signal 
> to ground. But, I am no expert, and could have interpreted 
> those circuits all wrong. Regards Rob 
Yup, I read the circuit the same way.


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