>Rich-
>
>The silastic /spacer idea is going in my hints and kinks file. Thanks!
>
ur welcome
>On another matter I have an Alpha 89 which has been a dog since birth.
>I have an Alpha 86 which has been a prince.
>
>The Alpha 89 has been a tube killer.
Do you have any kaput tubes from the 89?
> Alpha's story was that Eimac
>forgot how to me the 800 tube for a while after their transformation.
It's always the other company's fault.
>Eimac replaced the tubes twice, to their credit.
Eimac does not check tubes for gold sputtering damage.
>The amp first somehow
>blew its 30m input coil ( I don't think I ever ran it on 30m and used a
>50w "max" setting on my 1000MP). At that point--maybe after 100 hours of
>use--Alpha found the tubes to be delivering far less than rated power
>and Eimac replaced them.
When gold is sputtered off of the grid, it deposits gold on the cathode
-- which poisons emission. Gold sputtering is caused by vhf/uhf
parasites.
>All was well with the new tubes for about half
>a year and the amp seemed normal, but I had started to notice the amp
>had to be driven harder and harder (still less than 50w).
Eureka !
>After talking
>with Alpha I mailed the tubes back, they mailed them to Eimac--who found
>some sputtering in the tubes which they said indicated they were being
>overdriven-
Overdriven at HF can not cause gold sputtering. AT UHF, maybe.
>-who after a delay for a manufacturing run replaced them. By
>this time I had put an AL1500 into the main operating position and did
>not use the Alpha for a few months. When I fired it up even when
>running into a dummy load and with no drive supplied it would trip with
>an excessive SWR indication. In speaking with Alpha they described
>trouble with the connection to the output connector which would results
>in this type of behavior. I looked for the misalignment they described,
>found none,
chortle
>put the amp back together and fired it up. It worked
>perfectly on all bands except 10/12 meters. There, with maybe 10 watts
>drive, I could see the grid current, I could see the output going to
>more than 1.5kw and the grid current up into the yellow zone.
>
Sounds like oscillation.
>I parked the amp with the intent of talking to Alpha again and most
>likely taking the agonizing step of packing the beast for a trip back to
>Alpha--or another shop.
>
The fix can be done at home.
>I am starting to wonder if the constant trail of sorrows with this amp
>could be caused by a parasitic oscillation or something similar. Or
>from my vague description do you have a informed guess?
>
I agree with your guess. Hi-potting the tubes will give the answer.
>I have been very pleased with the old '86 which is still on the original
>tubes, though they are a little tired. Do you have any insight into
>Eimac, other suppliers, and the status of 3cx800's in general?
3cx800A7s have xtraordinarily high UHF amplification. Mo' is not always
mo' betta.
> I USED
>to think I would prefer an amp using them instead of what I viewed as
>the fragile and expensive 8877, but I am beginning to change my mind.
>Bob W2WG
>
Low Q vhf/uhf parasite suppressors should never be used in an oscillator.
>-----Original Message-----
>From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
>On Behalf Of 2
>Sent: Sunday, January 26, 2003 10:51 AM
>To: Floyd Sense; AMPS
>Subject: Re: [Amps] Reducing Ameritron AL-800H blower noise?
>
>
>
>>I wonder if anyone has looked at altering the blower mounting scheme in
>the
>>AL-800 or 800H to reduce noise? The blower is mounted directly to the
>thin
>>metal partition and a lot of noise is thereby conducted to the rest of
>the
>>cabinet. There's enough room to allow some flexibility in fan mounting
>-
>>perhaps some sort of gasketing material between the fan and the
>partition.
>>
>Small beads of Silastic rubber sealant make pretty good shock absorbers
>when cured. Put cardboard spacers under the mounting surface to suspend
>the fan while the rubber beads cure.
>
>- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
>www.vcnet.com/measures.
>end
>
>_______________________________________________
>Amps mailing list
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>http://lists.contesting.com/mailman/listinfo/amps
>
>
>
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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