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[Amps] Amp Supply LK-500 metering

Subject: [Amps] Amp Supply LK-500 metering
From: Ham H <>
Date: Wed, 14 Feb 2018 07:56:32 -0500
List-post: <>
I am working on an  amp supply lk-500 that has a strange metering problem.
The *plate current meter* reads in the reverse direction.  If I reverse the
meter leads I see current of only 100 MA and it does not change with
drive.  the grid current metering seems OK.

This was an estate find so status before is unknown,

Here is what I have checked:

All wiring is as shown in the manual
Shunt resistors are good
new caps, rect diodes and equal resistors
tried different tubes
check bias circuit and I see 9 V (9 V zener)
checked meter and it is OK
checked all grounds and looked for shorts in metering circuit.

I thought maybe it was a schematic error so checked equiv amps and mine is
wired as they are.

What could possibly be wrong as I am stumped and considering parting it out.

I can see that rect board has been worked on but unless someone miswired
something and the metering is not like every other amp I am lost.


Gary K4MT
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