[HAM] Hammond A100 and red caps.

[Kon Zissis]

Hi Don 
Whilst it is true that the wax capped organs sound mellower and thus
"warmer "  than  the post 1964 red mylar capped organs  or the recapped
pre 1964 organs , your friend is incorrect when he says that putting in
the red caps will make the organ sound more "electronic". What in fact
will happen is that the output levels of the tone wheel generator ( TG )
notes 49 to 91 will be brought back up closer to their original specs
and output levels thus approximately  restoring how the organ would have
sounded when it was new. 
 
Some  people  really love the mellower sound produced by the aged and
deteriorated wax capacitors  so therefore they are strongly opposed  to
the practice of recapping the TG . Over the years there have been some
needlessly nasty flame wars on the Hammond  forums over the issue of  TG
recapping. 
Apart from people's personal taste  preferences for the organ tone , the
technical reality is that if you want to closely restore the original
stock sound of the TG  notes 49 to 91 of the pre 1964 organs , then the
degraded  wax capacitors need to be replaced with new capacitors of the
correct micro farad  ( mfd ) values .
 
Replacing the wax capacitors with old red mylar capacitors is not the
technically  correct way to recap the TG because the replacement
capacitor mfd values   need to be specifically matched with each  of the
TG notes 49 to 91 filters in order to produce the maximum output levels
.  
 However if you are not so fussy about closely approximating the
Hammond factory capacitor matching procedure and getting the maximum
output levels  out of the TG notes 49 to 91 , then you can replace the
0.255 mfd wax caps of the TG notes 49 to 54 with  0.220  mfd capacitors
wired in parallel with 0.027 mfd or 0.033 mfd thus  creating a 0.247 mfd
or 0.253 mfd  value which would be approximately somewhere  close to
what the original 20 % tolerance rated  0.255 mfd wax capacitors were . 
For the TG notes 55 to 91 you can use 0.1 mfd capacitors which would be
approximately somewhere  close to what the original 20 % tolerance rated
0.105 mfd wax capacitors were.
 
If you do not really want to restore the full "new organ " brightness
levels but only want just a bit more brightness than what you are
getting now with the wax caps  , then for the TG notes  49 to 54 you
could use capacitor mfd values such 0.270 mfd and for the TG notes 55 to
91  you could use capacitor   values such as 0.150 mfd  . These mfd
values will allow the TG note 49 to 91 filters  to work a little better
but not at their  optimum  filtering levels thus producing the sound of
a wax capped organ that was a number of years old and the  wax
capacitors had started to drift up in mfd value  but the drift up had
not yet reached  the current 44+ years level of deterioration.
 
Despite the hype about capacitors  that sometimes appears on the
internet, in reality you do not need to use expensive audiophile grade
capacitors , you can use the cheaply availably MKT metallised polyester
types or the green cap types  for the TG.  The TG is not an ultra hi-fi
audiophile device.
The Hammond factory used high voltage rated wax capacitors because these
were cheaply and commonly available in bulk at that time and their size
was just right to fit on the filters ,  but the actual  TG note  49 to
91 output levels  were usually  somewhere between 13 to 20 millivolts
peak to peak  so therefore very low voltage rated capacitors are OK for
the TG. 
 
If you are going to do restoration work to your A100 , then it is a good
idea to replace the high voltage power supply  filter capacitors  , the
plate resistors , the screen grid resistors  and  the cathode resistors
in the AO28 preamp  and also replace the high voltage power supply
filter capacitors  , the plate resistors ,  and  the cathode resistors
in the AO29 power amplifier .
All the best.
Kon
 
Don Whitehead wrote:
I have a hammond A100 that is in pretty good shape, but I think the
sound could be a little clearer.  I was thinking of changing the
original capacitors (wax paper 1964) to the red capacitors I seem to
hear about so much. I read that the original capacitors were only meant
to last about 20 years max.  A friend of mine, who is a hammond
techinician, said he thought the organ sounded good, and that installing
the red caps will take the "warm" sound away and make it sound more
"electronic".  I don't get any "hum" or cracking, etc. from the organ.
I'm not sure if I should change them.  Was hoping someone here could
give me their opinion on this