[AMPS] Misc. Oscillations
Kessler Donald J LtCol HQ AFMC/DOOT
Donald.Kessler@wpafb.af.mil
Mon, 6 Mar 2000 10:50:48 -0500
>> Adjusting filament-v is simpler than tuning a tank. Several models of
>> Henry Radio amplifiers use approx. 6v on 3-500Z/8008 (4.8v) filaments.
>> How safe is that, Mr Subich?
>
>
>3-500Z's have 5 volt filaments, not 4.8. Your twisting of numbers
>reminds me of the national budget!
>
>
>73, Tom W8JI
>w8ji@contesting.com
Tom,
Actually the Eimac 3-500Z brochure states the filament voltage is 5.0V +/-
0.25V. By that definition, 4.75V should also provide full emission.
However, operating the filament at less than 5.0V, will certainly increase
tube life (also per Eimac). The math is easy... I operate my modified
TL-922s with approximately 4.8V on the filaments.
73 Tom,
de Don
>I have a TL-922, one day it went boom when I was using it. The band switch
>vaporized...yes vaporized. People told me I must have done it due to poor
>op practices. So, $80 bux later..I installed the new band switch.
Jerry,
I also had this happen to me. The 80m tap had completely vanished. I
replaced the switch, but then modified the amp. I have also personally sent
two bandswitches to other (DL) TL-922 owners. This amp eats bandswithes!
>...
>...
>But the point is, what ever the boom,boom, boom was..it hasn't returned.
>Many can postulate as to what I was doing wrong or what stars were in line
>with what planets..but as far as I can see, the mods that I did took care
of
>the problems I originally experienced. The best $20 bux I ever spend.
>If anyone has experienced similar probs with their TL-922 and have spent in
>excess of $400 bux in parts....try spending the 20buxs and try the
>"measures" mods. If you don't want to buy the parts from him, go elsewhere
>and try it. I would be interested in your results.
>
>
>Best Regards,
>
>Jerry K9GD
Jerry,
I own two TL-922s that I modified per Rich's notes. They are NOW very
stable. This is indeed the best money I spent. Based upon the high quality
of components in the kits and their low cost, I seriously doubt that he
could call this a "money making" venture.
I have also modified several other "ill-tempered" TL-922s, and their owners
are very happy with the results. Too bad the TL-922 is no longer produced.
It used high quality components and was well engineered (mechanically), and
with a few corrections, is a nice running amp.
GL Jerry,
de ki6sz
>A user with sufficient technical knowledge and concern over filament
>voltage issues should be able to easily add the proper rheostat or
>filament dropping resistor. Such a user can probably do it safely
>as well, unlike the legion of snake oil buyers.
>
>73,
> ... Joe Subich, W8IK
> <W8IK@Subich.com>
> <www.qsl.net/W8IK>
Joe,
Why wouldn't this be part of proper design and construction of an amp?!
Doesn't Henry possess "sufficient technical knowledge and concern over
filament voltage issues" to include this in each and every amp they produce?
If not, then why not?
I think it would be very enlightening to run an unbiased comparison of
design methodology and design implementation of the various amateur amps on
the market. The comparison could even include the warranty period and the
number and nature of problems encountered during the warranty period and
what the manufacturers responses were. Also, if design shortcomings were
identified, were these problems corrected in the next production run, and
were registered owners (outside the warranty period) notified of
improvements/upgrades?
Just a thought, but how would Alpha, mfj/Ameritron, Henry, etc., stack up
against each other?
73 de Don
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