----- Original Message -----
From: "j.a.hermans" <j.a.hermans@skynet.be>
To: "Paul Christensen" <w9ac@arrl.net>; <amps@contesting.com>
Sent: Sunday, October 06, 2002 7:47 PM
Subject: Re: [Amps] Failed 8877
> Paul,
>
> Have a look at SVETLANA.COM a russian factory. they have a lot of low-cost
> equivalents
> Looking myself for a good linear of about 700 or 800 wts
> have one here with those russian replacements of the 572B . More then half
> the price of the original ones.
> Good luck es 73's Jos on4kj
>
> ----- Original Message -----
> From: "Paul Christensen" <w9ac@arrl.net>
> To: <amps@contesting.com>
> Sent: Sunday, October 06, 2002 6:47 PM
> Subject: [Amps] Failed 8877
>
>
> > After 20 years of service, I experienced my first problem with my Alpha
> 77Dx
> > amplifier.
> >
> > I noted that the input VSWR into the amp was very high, zero plate
> current,
> > and only 40mA of grid current regardless of exciter drive level.
> >
> > I narrowed the root cause to a broken 8877 filament....although it was
> > difficult to find beacuse it is intermittent. At the onset of filament
> > current, it opens and after powering down the amp, and checking with a
> DVM,
> > the filamant resistance reads fine. I finally got it to read an open
> > resistance right at the pins with the transformer Molex connectors
> > unplugged. I can repeat the sequence and by putting the DVM in series
> with
> > the filament, I can see the DVM read AC current for a brief instant,
then
> > it goes to zero. When this occurs, I can then see the filament read
open
> > resistance right at the pins. Once I pull the tube and measure the
> filament
> > resistance, 75% of the time, I can then see good resistance. The other
> 25%
> > of the time, it will read open. I do not have a spare 8877 at the
moment.
> >
> > I'm not thrilled about a new Eimac replacement. Are there reasonable
> > sources of good pulls with ample life? If so, where should I begin
> looking?
> > Thanks in advance.
> >
> > -Paul, W9AC
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
>
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