[Fox_Tango] FT102 finals

[fox_tango@mailman.qth.net]

It is a poor practice to use different brands of tubes (valves) in the PA 
section...When you are dealing with two valves, it's bad enough, but when 
three are involved...Forget it.

All tubes are not alike.  It is best to use the same brand because the 
inter-electrode (excuse my spelling) capacitance of different brands are 
not quite the same.  Hence, when you replace the valves with a brands you 
must check the neutralization.  As a matter of practice you should check 
the neutralization periodically because of changes which take place in the 
valve after use.

As long as you use the same brand valve, matched-pairs should not be 
necessary...As a matter of fact, it is usually a waste of money.

My two cents..or pence.

73,
Jay/AF2C


At 04:54 PM 3/26/02 +0000, you wrote:
>Hello all.
>
>I've been following the FT101 finals thread with interest, and would like to
>ask a question that's been worrying me. A few days ago the PA of my FT102
>died, and investigation showed one dead and one suspect 6146's. I replaced
>these (Sylvanias) with a new pair of GE's, and the combination of two GE's
>and one Sylvania refuses to neutralise (perhaps not surprisingly). While I'm
>waiting for another GE, can anyone tell me if this will improve the
>situation, and how critical is it for the valves to be matched? It's easy
>enough to buy a matched pair, but a matched triple is much less common.
>
>73 de Mike GW4IQP GQRP SOC
>
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