[Amps] Life of 3CX800 tubes

[Carl]

A good sign of a weak 3CX800 and most tubes is that you cannot obtain full 
grid current, especially at low drive.

Id say the tubes are fine and that the exciter may be folding back from 
VSWR; try other bands.

Carl
KM1H


----- Original Message ----- 
From: "Bill, W6WRT" <dezrat1242 at yahoo.com>
To: <amps at contesting.com>
Sent: Thursday, December 10, 2009 1:16 PM
Subject: Re: [Amps] Life of 3CX800 tubes


> ORIGINAL MESSAGE:
>
> On Thu, 10 Dec 2009 17:20:35 +0000, Rick Stealey <rstealey at hotmail.com> 
> wrote:
>
>>
>>I have an Alpha 89 I am selling here for a friend who is no longer able to 
>>use his equipment.  I have a sale pending but the buyer is sceptical about 
>>the condition of the finals.  I have carefully tuned it up on all bands 
>>into a Bird load with a Bird wattmeter, 2500 watt slug.  Typical readings 
>>are 2500 volts, 1 amp, 60 ma grid current, and 1600-1700 out with 50 watt 
>>drive.  Increasing drive a little gets more grid current, but peaking the 
>>tune and load for max out doesn't improve things.  Power out doesn't sag. 
>>It's as if there was a governor on the amp !
>>Some say that amp should produce an easy 2200 watts and the tubes are 
>>soft.  If so what kind of life could be expected from them?  A tough 
>>question I know, depends on the use.  So maybe in percentage terms could 
>>it be estimated how much of the original life is left?
>
> REPLY:
>
> It sounds like the tubes have lost some emission, but as long as it 
> produces
> more than legal limit output, so what? Brand new tubes start losing 
> emission the
> minute you start using then. I would discount the price of the amp a 
> couple
> hundred bucks and go with that. If the purchaser wants brand new tube
> performance, let him buy some brand new tubes. You'll find a buyer 
> eventually.
>
> 73, Bill W6WRT
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