>I have a Ameritron 800H that I am having some problems with power output. I
>called Ameritron this week and they helped a lot, but still not sure if my
>amp is ill.
>
>The problem Ameritron ID'd was that my line voltage was down. It was
>showing
>a HV of 2,400V going down to 2,100V when transmitting. So they suggested I
>redo the transformer taps so that I set the amp for the highest line voltage
>at 230V vs the factory setting at 240 volts. This worked very well and my
>HV
>went up to almost 2,700V going down to 2,400V when transmitting. It
>increased
>my over-all average power from 1,300W to 1,750W.
** 1.2db makes no perceptable difference at the RX end on MF/HF.
>
>But I still need the IC756Pro to drive the amp with 110 watts to get this
>power and after about 30 seconds of pulse keying, the average power
>decreases
>down to about 1,400 watts. .
** This suggests that the 3cx800s have Ba migration from the cathode to
the grid. To reduce the rate of barium migration, operate the heater
just above the minimum rated V.
- What is the measured heater V in this amplifier?
>At 65 watts of drive, I'm only averaging about
>1 KW out but I don't see a power drop using pulse keying at this decreased
>drive level.
>
>Can anyone suggest anything else I can trouble shoot to get the amp to put
>out a steady 1.5KW with less drive vs what I'm having to drive it with now?
>Is this a tube issue? The tubes are only 2 years old- Also, when I turn
>the
>amp on, I hear a sizzling sound for a few seconds.........any chance that my
>over all problems are related to a troubled transformer/power supply??
** The AL-800 needs a step-start and a glitch resistor. Lower-Q vhf
suppressors might not be a bad idea. However, if an Ameritron amplifier
is ever returned for factory service with such suppressors, Mr. Tom Rauch
told me that he will have them "ripped out".
>Should I cut my losses now and just find a new amp or is there something
>obviously ablaze here?
>
** There is no such thing as a perfect amplifier. [see "The Nearly
Perfect Amplifier", *QST*, January, 1994) However, those who can solder
and comprehend English can pretty much arrive there by fixing the
oversights in a commercial amplifier. // Other improvements for
Ameritron amplifiers are:
1. Replace the high-tech RF-actuated bias switching with old-fashioned
in-sync bias switching so that the amplifier can not switch to non-linear
bias during soft-syllables of speech and generate feculence.
2. Install the high-speed switching mod. {<2mS, c.$60}
3. Remove any g-g "neutralization" circuitry.
4. Install a 50mm-75mm DC fan to blow air on the bandswith and tank.
cheers, Paul
* Murphy was right --"if anything can possibly go wrong, it will at the
worst possible moment".
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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