PS needed

From: <(>
Date: Fri Nov 28 09:41:04 1997

> At 00:02 28-11-97 PST, you wrote:
> >Date: Fri, 28 Nov 1997 00:17:07 +0000
> >From:
> >To:
> >Subject: Re: Needed: Power Supply
> >Message-ID: <>
> >MIME-Version: 1.0
> >Content-type: text/plain; charset=US-ASCII
> >Content-transfer-encoding: 7BIT
> >Bruce, Please ask other to rebuild that PSU this way. This is best
> >and much easier because the electronic components inside those PSU is
> >not that all strange and easily gotten. Capacitors are so cheap.
> ??? I'm not 100% sure I understand your syntax, but I think you're
> suggesting that I repair the existing supply. That's a great suggestion,
> and I would do it IF I had an adequate schematic diagram. Somehow, I don't
> think DEC would be willing to part with such anytime soon.
> Unless someone can suggest what component to look at (I think it's the +12
> supply that's popping on and off), I will continue to pursue a replacement
> for now.
Take both keyboard, mouse off the machine just in case, When
diagnosing the power problem, I always take ALL detachable parts off
and try each one by one until I nab the guilty party.

First, unhook all 3 hard drives and throw the power switch and see if
you can wake up the computer. Then hook *one* hd just by power only
and try, then power off, hook the scsi cable back on, pin 1 to
pin 1 on motherboard see that also striped side of ribbon cable
next to power connector and try again. Stripe is given as pin 1
wire. Those RZ23 is conners 100mb I think, and does only draw less
than 8 Watt each at spinup.

In my repair, I test for opens and shorts in power
semiconductor components, visiually eye all passive comonents for
burns or deformations (capacitors tops bulged or blown open, smelly
if soldering that capacitor's legs). But now I could do better now
that I got ESR meter to check most of capacitor's health. This does
not require that shematics to do that! I never had one at all
fixing anything from VCRs, TV's, monitors, even computer boards.
Also check all power resistors for opens and creepage in resistance
changes from rated markings. Most of trannys are like two diodes
back to back. And FET and MOSFET have bit different reactions to
meter probing when in circuit and out of circuit. In any
switching or linear power supplies easier to disconnect just one big
transformer totally out of circuit to get best meseaurements.

When I find one or few power resistors (usually fusiable resistor)
totally block of carbon, look at other living PSU of same make or
jump on the sci.electronics.components or to
get correct resistor values or ask here!

Received on Fri Nov 28 1997 - 09:41:04 GMT

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