[AMPS] amplifier problems

[Jamie Jones]

A lot of time the step start resistor in this units blow because a too large
fuse was in place; it should be a 1 1/4 amp slow blow ceramic fuse.
It will  also blow if  the relay contacts are bad ( open frame crummy little
things -- bad design to use it in the first place had to change a lot of
them during my time working for ETO ( when Alpha Power was still ETO ). It
also fails with a too large fuse AND the crow bar down with open case (HV
short) and also of course one of the 8874 shorted ( have seen a few of them
:-) ). A 20W resistor will work fine in this application I installed a few
of those.

Jamie


----- Original Message -----
From: Gilmer, Mike <mgilmer@gnlp.com>
To: 'AMPS' <amps@contesting.com>
Sent: Wednesday, October 13, 1999 12:36 PM
Subject: RE: [AMPS] amplifier problems


>
> On Wednesday, October 13, 1999 12:05 PM, measures
> [SMTP:measures@vcnet.com] wrote:
> > >
> > >On Wednesday, October 13, 1999 10:20 AM, measures
> > >[SMTP:measures@vcnet.com] wrote:
> > >> >
> > >> >Hello all...have an old alpha 374   the resister across the step
> down
> > >> >relay, a 10 ohm 13 watt wire would burned up....question...can I
> > >replace
> > >> >this with a 10 ohm 20 watt, what I have available or should I
> replace
> > >it
> > >> >with an exact same wattage???   thanks all   Tim   WB8OWX
> > >> >
> > >> I have seen ww resistors of the same physical size rated from 10w
> to13w.
> > >
> > >Your point?
> >
> > The ratings game is just that.   13w rated and 10w rated vitreous
> coated
> > ww resistors are 2 inches long and 0.4 inches in diameter.
> > >
> > >>  A 10w, 10-ohm resistor should probably work ok in this
> application.
> > >
>
> It sure gets crowded on a head of a pin.
>
> He has a 20W unit, apparently in hand.  Why would you feel it necessary
> to tell him a 10W would work and not answer his specific question and
> tell him if a 20W is OK?
>
> >
> > >
> > >> However, there is a chance that the resistor was not defective in
> the
> > >> first place, and there is a circuit fault which caused the failure.
>
> > >>
> > >
> > >True enough, but since a 10W "should probably" maybe it "might not".
> >
> > My guess is that a 7-watt rated unit would work in this (intermittent)
>
> > application.
> >
>
> Maybe even smaller. In this application it probably depends more on its
> construction than its power rating per se.  I agree the real problem is
> why it "broke" in the first place. If being underrated caused the
> problem then bigger will be better. If not, then it won't help much -
> just cook longer probably.
>
> I'd treat it much like a blown fuse: replace it once and see what
> happens - if it blows again, troubleshoot.  Unlike a fuse, it probably
> won't "blow" right away even if there's trouble.  So there'll be time to
> see (smell?!) if the rest of the circuit is operating properly.
>
>
> Ciao
> Mike
> N2MG
>
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