Re: sick '70 power supply?

[Dave@PHOENIX.SCH.Symbolics.COM (David A. Bentzen)]

    Date: Tue, 24 Mar 1992 16:22 PST
    From: paul@PERSEPHONE.aegean-sea.dialnet.symbolics.com (Paul Cross)

    I've got a 3670 that upon power up does not turn off its fault light.  I
    noticed that the main -12v light on the back back of the machine was not
    lit, though all others were lit.  I don't know if the bulb is burnt out
    or if indeed there isn't -12v.  On checking my powertec power supply,
    model 6JA5-BBF-17, all the channels were normal except channel 3, which
    was putting out 1v instead of its labeled voltage of 12.   The
    machine was fine this morning.  I had to power it down to do a board
    swap.

    My questions.

    What is the minimum board set one could put in an OBS machine and
    have the fault light go out upon power up?

The minimum board configuration to allow the fep to run on an OBS system is:

Fep, Fep Paddle, I/O, I/O Paddle

    Can I adjust the voltage of channel 3? Or, is there a fuse or breaker
    that could have tripped?  Or, do I need a replacement power supply?

Yes you can adjust the voltages on all of the channels, but I think in
this case it will do you no good.  Your power supply is most likely
"hosed, broken, out to lunch, Kaput etc.   

David A. Bentzen
Corporate Technical Support, Symbolics

Phone: 818.998.3600 
Phone: 800.824.4263
Email: Dave@Phoenix.sch.symbolics.com