[Heathkit] SB-1000

Fri, 20 Feb 2004 18:07:10 -0500

D401 on the PS board is shorted; when that happens the tube gets zero
bias.
Replace with a real diode, 1N5408.

Carl

----- Original Message ----- 
From: "Charles W BWW Burkhardt" <[email protected]>
To: <[email protected]>
Sent: Friday, February 20, 2004 4:03 PM
Subject: [Heathkit] SB-1000

> First let me thank all who responded to my request for help in
> establishing the tube bias for the 3-500z and replacing the 0.6 ohm
> resister for the plate current metering circuit. I found two 1.2 ohm,
1%
> resistors for the meter and used 10 3 amp 1000V diodes to replace the
> Zener. Both of these changes seem to work well. Plate current responds
> and the grid current is within bounds.
>    I am now back to the  original difficulty, which caused all the
> problems. When I use a moderate amount of plate current-about 100 ma-
and
> low grid current of about 80 ma, the tube plate glow red. MOderate
> amounts of power, say 150 watts, cause the  plate to turn orange with
cw
> keying. If I send too long (into the dummy load)sd0 I blow a fuse. Bad
> tube? Any ideas will be appreciated. Thanks, Charlie, K0GPF
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