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[Amps] AL-80B questions

To: <amps@contesting.com>
Subject: [Amps] AL-80B questions
From: 2 at vc.net (rlm)
Date: Sun Mar 9 10:40:59 2003

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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