[TowerTalk] TL-922 grid chokes

[Jim Thomson]

Date: Wed, 4 Aug 2010 10:34:40 -0500
From: rcm at mail.icnet.net (Randall Mullinax)
Subject: [Amps] TL-922 grid chokes

The grid chokes in my TL-922 were replaced with 10 ohm resistors 
by the previous owner.  The amp works fine except on 10 M where the 
resistors go up in smoke within a few seconds.

This bring up several questions.

1. Is the amplifier oscillating on 10 M?

2. Should I replace the resistors with the factory 470 uH chokes 
or directly ground the grids?

3. Where can I get replacement grid chokes?

4. I?ve read about adding/increasing negative feedback.  Does anyone 
have suggestions?

Thanks for any and all comments.

Randy
AD5RM

## I have worked on a  couple of TL-922's yrs ago.  I remove the 6 x grid caps
and 2 x chokes..toss em.... and strap all 6 x grid pins to the chassis, with copper strap. 

## your drive requirements  will drop  by 20-25 watts on ALL bands.   
The amp will be stable as a rock.    Since your xcvr is now operating with
20-25 w less drive.. the xcvr's  TX IMD  will be much better.  

## Overall  signal quality will be  better.   IF  you want a real grid fuse, use a 
3agc type.. and insert it in series with the existing grid shunt. [either side]

## I installed a 3agc fuse holder on the rear of my 4 x L4B's... with  a FAST
rated  250-300 ma rated fuse.  If the grid fuse blows open... there is now
now path  for dc grid current.   Power output drops to zero.  Input swr
will rise to infinity.   Xcvr will reduce it's PO..down to nothing.    Takes
4 x seconds to change the fuse.    I have blown one fuse since 1990. 

later....... Jim   VE7RF