Agreed, that is the one thing i did do, is replace the zener, but no
change. Looks like it is a bad tube, after swapping and pulling, the
problem follows the one of them. So now for a little market research i
guess.
Tnx
Rich
On 10/2/2014 2:05 PM, n8de@thepoint.net wrote:
Sounds like a faulty bias zener.
Don
N8DE
Quoting k0zx Rich <k0zx.co@gmail.com>:
Wonder if anyone has experienced this failure mode with this or a
similar amp:
This amp is 80s vintage and since then has been a solid performer,
grounded grid with two 3-500z. But it has a developed a problem where
at power up (no rf drive, ant relay input not active for tx), the plate
current rises to about 3x normal (about 300ma, 100 is normal), stays
there for 5 to 10 seconds and then drops to zero.
If enabled to transmit with antenna relay input on, plate idle current
is normal, going from 0 to 100ma.
If apply rf in, it will output but at only about .6 or .7 its normal
output.
After inspecting the schematic am not seeing an obvious source for the
problem.
Any suggestions appreciated
Rich
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