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

[Robert Thain]

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.