On Sat, 06 Feb 1999 08:38:53 -0500 Scott Gordon <firstname.lastname@example.org>
>Here is some background. The amp is running two 3-500Z. I just
>out the power supply from 110v to 220v. Plate voltage two tubes
>idle 2500 volt key down.
>Let's take 40 meters into a dummy load:
>I thought I may have a soft tube, but now I don't think so..
>1 - Tube installed driving from the Kenwood TS-570 100 watts of power
>using the auto tuner for my tuned inputs.. 1100 Watts out on 40 m
>I can put the other tube in and replace this one and get the same
>thing. I key down and talked for 20 min in the dummy load on each
>and they hung in there at 1100 watts. I have since tried each tube
>seperatley in both sockets. Same thing 1100 Watts.
>If I put two tubes in there retune the the auto tuner and the amp, I
>nearly 1500 Watts out. But this never last very long. It keeps
>back to 1000 to 1100 watts with two tubes.
>Now I understand I am really driving that one tube with 100 watts
>some percent of loss via the auto tuner. And when I put two tubes in
>there impedence changes and now I am only driving each tube half the
>watts or so. So straighten me out? Why am I seeing 1400 to 1500 at
>then it falls back with two tubes? But with one tube it stays pretty
>constant at 1100?
>Any info would be appreciated,
I would suspect that you are having a case of component drift at the
higher power level. If it is all bands I would start with the plate
If it is band limited then look at those unique parts, particularly any
fixed value caps.
Something else to consider is a undersized plate choke or RF heating due
to a close resonance.
73 Carl KM1H
>Scott 73's KQ8RP
>FAQ on WWW: http://www.contesting.com/ampfaq.html
>Administrative requests: amps-REQUEST@contesting.com
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
or call Juno at (800) 654-JUNO [654-5866]
FAQ on WWW: http://www.contesting.com/ampfaq.html
Administrative requests: amps-REQUEST@contesting.com