Possible regulator problem in 11/34

Tony Duell ard at p850ug1.demon.co.uk
Tue Nov 15 13:43:33 CST 2005

> Well, I was working on my 11/34 last night, and I noticed when I flipped it
> on its side that the power regulator H745 does not have its red light on.
> Does that mean the other two H744s are problematic, or does it mean that the
> H745 is the problem, or is this all normal?
> Opinions please! :)

On these DEC power bricks, the LED (originally a filament bulb) is simply 
connected to the output (with a series resistor, of course). It should be 
on when the supply is operating.

If it's not, then either the PSU brick has problems, there's a short on 
the output, or (of course) the bulb/LED has failed.

I would grab a voltmeter and check the voltage at the backplane. And then, 
if necessary, look at the printset to debug the regulator brick.


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