[Amps] GS35 144MHz amp faileur, how should we test

[Tony King - W4ZT]

Robert,

What is the idling current with no drive (ZSAC)? Do you have a method to 
vary the bias? I assume that you have some protection circuit active. Do 
you know which one is tripping?  Grid or Anode? Does the grid meter jump 
up when the failure occurs?

73, Tony W4ZT

Original Message
-----------------------------------------
To: 	amps at contesting.com
Subject: 	[Amps] GS35 144MHz amp faileur, how should we test it.....?
From: 	Robert Thain <g0hgw at yahoo.com>
Reply-to: 	Robert Thain <g0hgw at yahoo.com>
Date: 	Wed, 5 Jul 2006 05:40:27 -0700 (PDT)
List-post: 	<mailto:amps at contesting.com>

Hello,

I am contacting you on behalf of our radio club.
Last weekend we had a failure of our 144MHz GS35 amp.

This amp is relatively new (about 100Hrs of use) and the tube was new. 
The amp
and tube was commissioned properly.

How should we test the tube to see if its OK ?

The symptoms were , Once the HT had increased to about 3KV there would be a
loud clanging from inside the amp, then the HT would drop, probably the
protection kicking in. Some time there would be  delay of a few minuets 
  before
it would 'clang and cut'. However every time we tried to transmit it would
systematically 'clang and cut'.  The clanging was very loud and sounded
mechanical, like hitting the side of a thick metal box.


We opened the amp, there were no physical signs of damage, IE no burn 
marks or
signs of arcing.

We will have an autopsy party on Friday evening.

We will start by checking the GS35 , and then see if the Power supply / 
HT is
working correctly (with no load).

If you can point us in the right direction please send me a mail.
G0HGW(at)yahoo.com  (at) = @  (This is to try and reduce any spam.)
thanks Robert

PS I am still looking for some valve bases for 3CX100 / 2C39.