>
>Greetings,
>
>I have a 1KD-5 that I've been told has been
>distorting. The symptoms described lead me to
>thinking there was a PS problem.
A single 3-500Z will distort when driven by more than c. 65w at this
anode V. A workaround is to add some R in series with the cathode drive
coupling capacitor to develop RF-negative feedback. For 100w drive it
takes c. 25-ohms.
>The amp was given to
>me a while back with a bad transformer. I just
>replaced it at the time and used it for awhile without
>doing any other checking.
>
>In searching for the cause of the described
>distortion, I ran across something that I'm not sure I
>understand. The amp has 2 large rectifier modules
>(Semtech SDHD-15K) that measure a little better than
>10 meghoms in the forward direction with a DVOM.
HV rectifier stacks need to be measured in the forward direction with at
least 1v per P?/P/N junction. DMMs typically supply c. 1,5v max. In the
reverse direction, rectifiers need to be checked for piv with a high-pot.
However, if a HVPS is making normal V, the rectifiers have gotta be ok.
>Having never worked with these devices I'm not too
>sure, but I'd think that there's something wrong here.
>
Your 3-500Z may be distorting because it is running out of emission due
to the use of c. 5.8v on the approx. 4.8v filament. When a 1KD-5 is
operated in Japan, where they have 200v mains, the filament v. is ideal.
Typical emissive life in the U.S. is c. 200-hours in a stock 1KD-5. Does
Henry Radio sell replacement tubes?
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|