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[Amps] Ameritron AL-811H - Question

Subject: [Amps] Ameritron AL-811H - Question
From: "D Pipes" <>
Date: Thu, 5 Jul 2007 13:58:33 -0600
List-post: <>
While surfing the net killing time I stumbled onto a "repair" for the AL-811H 
amp. It is on

The fellow posting the repair stated that when keying this amp there should be 
no current showing on the grid meter (no power from exciter just using radio to 
key amp). He said that in many cases D16 a rectifier diode will fail and cause 
you to see current flow on the grid meter. His he said was 30 ma keyed no 
power. Well I tried it with mine and sure enough I noticed 35 ma when radio 
keyed the amp. I happened to also notice that the plate current was only about 
75 to 80 ma (book says it will be around 125 plate current at idle.

Well I cut out the D16 diode replaced with another 1n4007. 1000v 1 amp. rect 

Sure enough grid current remains at zero now when keyed and to my surprise the 
lost 35 ms current seems now to of corrected the plate current which is just 
about exactly 120 ma very close now to the 125 stated current.

Here is his entire paragraph on
This fix is for the ameritron AL811 amplifier.
Problem is high grid current reading (mine was approx 30mA) with the amp keyed 
and no exciter drive check D16 on the schematic which is a general purpose 
rectifier diode 1N4007 1 amp max current 1000v reverse voltage needs replacing.
The 1N4007 diode acts as a fuse for temporary anode to grid shorts and is 
located on the top board(right hand side)same board as the tank coils. It is 
nearly ALWAYS this diode that causes the problem not the tubes.

My question.. I know the repair DID infact correct a problem I didn't not even 
know I had. What improvements or better said what affect does repairing this 
diode have in the function of the amp.

I did check the cut out diode it was confirmed defective.. 
Anyway, no big deal but I know this group will know what the diode really does 
and how the affect may or may not have on the amp.

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