Amplifiers that happen to have tubes with lower than average VHF
amplification tend to be stable.
>
>I currently have a AL80A, purchased used. It still has the original
>tube, the amp sn is 0156 so it's an old one, perhaps 15 years or more
>old. It runs good with 70 watts of drive I get about 800 out, I have
>had it up to 1100 out for a short time to get the tube nice and hot,
>I don't normally run this amp that hard, some do. I don't think this
>amp has any parasitics, but I have not tried this amp yet on the
>higher bands, 15,20. Don't have the ten meter conversion yet, by the
>way anyone know whats involved to make the AL80A work on ten? I did
>have to replace a resistor in the Hv meter circut, it had changed
>value from 1.5 meg to 2.8 meg.
Few amp designers seem to read the fine print in the mfg-specs for HV
multiplier resistors.
> I also installed a step start circut.
>This is a nice amp for the money and it will get within a couple of
>db of the legal limit, SSB. I don't think I'd use it for rtty though.
>
>Prior to the AL80A I had a TenTec Titan, which I purchased new and
>had it for 12 years. It still has the original tube
Only one tube. There were two models?.
>and still puts
>out full rated power plus. I have never had a pop
Amplifiers that use tubes with gold-plated grids reportedly make little
or no sound during an oscillation condition that evaporates gold off of
the grid.
>or anything that I
>could say was a problem in that amplifier, no parasitics.
>
>Prior to that I had a used Alpha 76CA, it also put out the full rated
>power plus and I had that amp for several years, never any hint of a
>parasitic or any problem of any kind.
>
>Prior to that I had a TL922 which I purchased used from another ham
>here in town, again never any hint of a parasitic. The only problem
>I had with the 922 was that big clunky changeover relay, I had to get
>in there and clean the contacts a couple of times. This amp I was
>always a little leary of though, don't know why, maybe it was that
>big relay. A very cool running amp though and put out a lot of power.
>
>Prior to that I had a L4B by Drake, again purchased used, never a
>hint of parasitics or other problems although I did have to replace
>the tubes right off the bat as they were soft, I knew this when I
>bought it, the guy was honest and told me they needed replacing, the
>price was right as I recall. A local purchase. The cabnit rattled
>and buzzed though so I lifted one corner and stuck some paper under
>one foot, that quieted it down some. I had this amp for about 3
>years.
>
>Prior to that I had a used SB200, (ho-hum) never a hint of
>parasitics, no problem of any kind with that amp, although it only
>put out 500-600 watts, but that was my first amp and I may not have
>been driving it very hard as I am a rather conserviative operator
>especally back then. In all fairness I never operated on the upper
>bands with this amp, so I don't really know if it had any weirdness
>or not.
The first casuality in a SB-200 from a parasite is typically a toasted
80m Tune-C-padder (100pF) contact on the bandswitch. Unless the
amplifier is operated on 80m, the padder's missing contact is not missed.
>
>Now after having all those amps and no problems you can see that I am
>skeptical as to amplifier instability claims.
Of course. Most people never have experienced a parasitic. However, I
am not in that group and I happen to be a curious guy.
>If you're careful
>about tuning up and don't grab the band switch instead of the tuning
>knob (TL922), keep the thing loaded a little bit heavy I think and
>don't try to load up a ground, also keep your antenna and feedline in
>good condition, you should be ok.
Please explain how the tank V could increase when the tank is out of
resonance.
> I don't know whats wrong with your
>freinds amp, I hope he gets it resolved soon, it seems to be going
>thru tubes like crazy.
>
>By the way out of all the amps I've had over the years the Alpha 76CA
>was my favorite. Something about those older Alphas that I liked.
>The tubes are pricey though, $400 or so each!!
>
Every Alpha owner I have talked to who seemingly had a 3cx800A7 fail
received a new tube at no charge, even when the tube was out of warranty.
>Does this help? I know you wanted slightly different answers, but I
>couldent help telling my story.
>
>73
>Dale K9VUJ
>
>
>
>
>> Therefore, I'm curious to know if there are others on this
>>reflector who've experienced similar problems (any brand amplifier)
>>that have been successfully solved with the AG6K ( or another design
>>) VHF supressor. To round out the study, one would also need to know
>>if someone had installed such a thing and found that it *did not*
>>solve the problem it was intended to correct, or if it caused other
>>problems.
>>
>>I wonder if Amperex is making master cylinders? I just replaced it
>>on my Volkswagen for the 3rd time this year.
>>
>>
>>Sooooo much to learn..... Sooooooo little time
>>
>>
>>Kind regards all
>>
>>Randy DuCharme (AD5GB)
>>--
>>Microsoft is NOT the answer
>>Microsoft is the question and the answer is NO!
>>
>>Proud to be 100% Microsoft Free
>
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>
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
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