From: "Hans Otto Pyndt" <oz5dx@adr.dk>
To: <amps@contesting.com>
Subject: [AMPS] Parasitics in Yaesu FL2100B
Date sent: Sun, 8 Aug 1999 20:45:53 +0100
>
>
> I have problems debugging a FL2100B after I installed a pair of Svetlana
> 572B. It has blown several 33 ohm grid resistors with a big bang. The grid
> is not directly grounded but decoupled with 200pF. Bias is supplied via
> the 33 ohm. Bias supply has been modified to a voltage doubler a la
> Svetlanas suggestions and the tubes are cut-off in stand by. No-signal
> current is adjusted to 30 mA. I have had this problem occasionally with
> the original Cetron USA tubes, but after I changed the grid resistor to 47
> ohm, 2w, I have not seen this problem. However with Svetlana tubes the big
> bang occurs nearly immediately. Luckily the tubes have survived so far.
> Any suggestions? 73, Hans, OZ5DX
The tubes are bad. Have them replaced with properly tested tubes.
73, Tom W8JI
w8ji@contesting.com
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