[AMPS] 3-500z going dead?

[Phil T. (VA3UX)]

At 12:16 PM 2/20/2000 -0600, you wrote:
>
>Hi All,
>
>I have a little Henry 1KD5 (single 3-500z) amp and I think the tube is going
>dead.  I dont have a lot of experience with 3-500Zs so bear with me here..
>The tube has a 1982 date code so its an older Eimac.  The amp has been
>working fine for the last month (I use it every day for 3-4 hours), but the
>output now will drop pretty fast when tuning.  The odd thing is as the
>output drops the input SWR goes up.  It will level off then the power will
>climb a bit.  It will drop from about 850 watts to 600 in about 5 seconds,
>and the input SWR climbs from 1:1 to 2:1 in that same time period (even with
>a tuner on between the radio and amp the output power still drops the same
>amount with a constant 1:1 SWR).

Kevin, the same symptoms would occur if a component in the input matching
network(s) was failing.  I don't know the 1K5D so I don't know what is in
it.  But failing input components that change value when subjected to some
power, would change value and change the input SWR.  AS the SWR climbs,
less drive power is available to the tube and the output power would drop.
Check all the solder joints in the input path too, including the filament
pins.

Just some ideas to work with

Phil


  The HV and grid current does not change
>but the plate current drops.  It has been gradually getting worse and 10m
>output is also down a bit from when I first started using it.  I dont mind
>buying a new tube but I hate to waste the $$ if this sounds like something
>else is wrong.  BTW, I replaced the filter caps when I first bought it...
>
>73,
>Kevin
>KB9UPV
>
>
>
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>
>


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