Central Electronics 600L Amp

[Alan Gutfrucht]

Hello,

I am hoping that somebody out there can help me with a problem that I am
having with a Central Electronics 600L linear amplifier. I bought this unit
used as-is a while back and just tried to put it on the air recently. It
does not work and exhibits the following problems:

I let the filaments warm for several minutes. When I turn on the plate
toggle, I get over 400 watts input indicated without applying a signal. The
manual says that I should be able to adjust the screen voltage control on
the rear panel to indicate 70 watts input with no signal applied. The screen
voltage control makes no difference.

I show no output or indication in any of the other meter positions. No grid
current and no RF amperage. This occurs on all bands.

If I leave the plate switch on too long (more than 5 seconds), the plate
overload switch will trip.

The last unusual thing about this 600L is that I lose receive sensitivity
through it if I connect my antenna to the "Input" SO-239 on the rear. If I
connect the  antenna to the "TR Switch" SO-239, the receive sensitivity is
normal.

Could I possibly have a bad 813 final? The manual states that the plate
overload will continually trip if there is a plate voltage short.

I will appreciate any ideas or comments on this problem.

73, Alan WB2FZC

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