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[AMPS] Titan 425 amplifier problems

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Subject: [AMPS] Titan 425 amplifier problems
From: (
Date: Wed, 26 Sep 2001 22:17:11 EDT
A friend of mine is looking at purchasing a used Titan from an estate sale.  
It's not been used in a while.  The seller claimed to have recently tested it 
at 1KW out.  He did state that there appeared to be a problem on 15 meters.  
I did notice that the  factory installed collar to keep one from turning the 
band switch to 10M had never been moved from the blocking position.

When first turned on the amp blew the PS fuses (think they were not slow 
blow).  When it started up without blowing the fuses, and  it came off the 3 
minute warm-up, it showed .3 amps plate current without being keyed.  The amp 
was opened up and tubes pulled, blown out, visually inspected and some 
corrosion on the plate cap connections was removed.  When turned back on, amp 
starts up normally (like mine), HV seems right and it seems to be keying 
correctly in QSK with a TT Omni 6 with the amp feeding a dummy load. 

The problem - no output with 20-30 watts in, no movement of the grid current 
meter or plate current meter, no dip in HV supply when keyed in CW.  Input 
SWR on 20 was 2 (mine is 1.1-1.2) .

I've set the amp down next to mine and compared the two.  Other than a few 
component changes (mine's probably a few years older), we could not see any 
significant differences.  The amp did not perform any differently on my PS 
than it did on it's own (and yes - my PS still works). 

Is there any easy way to tell if the tubes are shot?  

Can the amp be run with just one tube at a time to test each tube?

How much risk am I taking if I try my good tubes in his amp???

Any ideas of what else to look for?

I've owned about 10 different used amps with various tubes and never had any 
significant trouble.  Can't say that for the numerous used HF radios that 
I've bought!

Ralph N4TG

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