Start with basics. Remove the tubes and trace thru the voltage path from
line cord to plate caps. Something is touching, misswired, shorted, or
whatever.
Carl
KM1H
----- Original Message -----
From: <walnutcreek@appstate.net>
To: <amps@contesting.com>
Sent: Thursday, November 08, 2007 8:05 AM
Subject: [Amps] SB-230 converted to two 572bs
> Hi all,
> I have in my possession this amplifier. The conversion was done by an
> unknown ham in NC. The conversion includes a filament transformer. Alas,
> I have a problem.
> First off I'll list the items I addressed after the amp blew the bias
> supply cap.
> I have replaced the diode, resistor, and cap for the bias supply. Diode
> and Cap. were bad.
> I have also replaced all diodes on the power supply side of that board.
> Saw arcing so I replaced them.
>
> I also found two of the rectifier caps bad and replaced all six.
>
> Now my dilemma,
> When I plug in the unit the fan comes on, filaments light, meter lights,
> and meter shows 1500V in the HV position without the power switch being
> engaged.
>
> When I engage the power switch, the fan turns off and filaments go out,
> the meter light brightens and the meter shows 2600 V.
>
> Interestingly enough, right after I replaced the components above, the amp
> worked fine...and then I pwoered it back up to get these results.
>
> Where is my next turn, I think I may have to draw a new schematic on this
> thing, but don't have the time right now.
>
> The amp used to make 600 watts output easy, I ran it at 550 watts out on
> the Bird due to transformer weakness in a 572b application. Any help will
> be greatly appreciated.
> Tnx es 73,
> Cam
> WA4JKW
>
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