For reference, the original 3CX800 tubes in my 87A, which is going on 15
years old, are still producing full output (>2200W) into a dummy load on
160m-10m.
If the 89 is anything like the 87A, which I believe it is (i.e., same amp,
not automated), then your voltage is too low. It should be closer to 3000V.
My 87A idles with the HV LED one position to the left of the maximum 3000V,
which is somewhere in the range of 2850V.
But don't despair. I suspect your voltage is lower because you have the
SSB/CW switch in the CW position, which lowers the HV to around 2500V.
Consequently, the amp won't produce full output. I've made this mistake many
times on my 87A (i.e., moving the amp and accidentally changing the switch
to the LO position, then wondering why I can't get full output power.) I
believe Alpha will tell you that the amp should never be tuned or run in the
CW position. It's only there for FCC compliance reasons (i.e., ensuring that
peak power on CW doesn't exceed the legal limit.)
Try tuning the amp with the switch in the SSB position and I think you'll be
pleased with the results.
73, Dick WC1M
> -----Original Message-----
> From: Rick Stealey [mailto:rstealey@hotmail.com]
> Sent: Thursday, December 10, 2009 12:21 PM
> To: amps@contesting.com
> Subject: [Amps] Life of 3CX800 tubes
>
>
> 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?
>
> Rick K2XT
>
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