[AMPS] Henry 1KD5 Rectifier question

Randall DuCharme ad5gb@yahoo.com
Sun, 28 Oct 2001 05:55:58 -0800 (PST)

--- 2 <2@vc.net> wrote:

> >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.  

I didn't think that I was driving it even that hard...
but will double check.... and be sure to keep it below
the 65W level.  It seems to me that if I get too much
higher than that, Ig gets too high anyway.

> >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.  

I didn't realize that these were diode stacks.  I
guess I thought of them as a single ( or in this case
double ) diode device. TNX

> 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.  

Interesting.  This possibility I never considered,
since I was able to get good output ( 600 watts or so
) with reasonable drive.  Since I don't know what the
orignal transformer supplied, I can't say first hand
what the conditions were before I got the amp.  

> Typical emissive life in the U.S. is c. 200-hours in
> a stock 1KD-5.  Does 
> Henry Radio sell replacement tubes?  

I don't know.  The should maybe furnish them gratis if
they designed the amp so that it operates outside of
the tube manufacturer's specs.  :-)

Actually, I hope to have my 4x813 project amp running
soon and won't need to bother with this any further. 
Are you available for on-air testing? :-)

Thanks much for your time and thoughts

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