[AMPS] 8877 amp failure

[Steve Bookout]

Hello everyone,

Right after the CQWW CW contest I asked for a bit of guidance in figuring
out what was wrong with my home brew amp.

I received lots of suggestions and request to let people know what I found.
 Those Emails were lost due to a system problem, so am answering to the
reflector.

I got no plate current indication, lots of grid current and it quickly
tripped the grid circuit.  HV was fine.

I used a 1 watt zener to set the bias and a large transistor to handle the
power.  This is a widely used circuit.  This zener was open.  The bias was
way beyond cutoff.
The original problem was that the HV took a short cut thru the side of a
Millen HV connector to the chassis.  My B+ surge resistor did it's job but
lost it's life in the process.  Apparently, this is when the zener went also.

Haven't actually tried it, but I know that it surely won't work with an
open zener.  Time has been limited to work on the amp, but will try to fire
it up today.

Thanks for all the advice.

73 de Steve, NR4M


---------------------------------------------
Steve Bookout, NR4M (ex NJ4F)
Rapidan Data Systems

'DX4WIN...The way logging programs should be!'
Free demo at http://www.erols.com/pvander

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