[HAM] Generator output levels

[Kon Zissis]

Hi Alan and everyone.
Yesterday and today I having been adding new TG measurements into my TG
data spreadsheet and I hope to finish this later on today or tomorrow
and then I will send a copy of the updated  TG spreadsheet to Hammond
Wiki and also to those who have asked me for a copy via email attachment
data. There are now more than fifty Tg output curves in my TG data
spreadsheet and this is indeed very interesting to look at.  
 
>I spent a little time looking at Kon's generator output data. Really
interesting. I found 
>that I could look at the curve and could guess (with a fair amount of
accuracy) the age of 
>the organ and whether it had wax caps. 
 
Usually the wax capped output curves are very obvious with the sudden
drop off starting at the TG note 49 onwards. Most of the wax capped pre
1964 organs and the red mylar capped post 1964 organs in my TG
spreadsheet have similar output  levels in the TG notes below 49  which
have not seem to have changed due to ageing like the wax capped TG notes
49 to 91  did.
 
   
>1. The Mihevic 1959 C3 with wax caps shows a curve very similar to the
mylar 
>capped organs, which was surprising.  Then I noticed that this reading
was taken in 
>1972. So maybe it would be more typical if re-measured today.
 
The Mihevic 1959  C3 TG data from 1972 is very valuable because it
reveals that the pre 1964 wax capped organs basically had a similar TG
output curve to the post 1964 red mylar capped organs. It would be
interesting to see  the current TG output levels of this 1959 C3 with
the now aged wax caps.
Interestingly the Mihevic 1956  B3 was also measured in 1972 and  with
this B3 the wax capacitors were already ageing and the output levels  of
the TG notes 49 to 91 were dropping off as can be seen in the 1972  TG
output curve. The more recently measured TG output curve of this same
1956 B3  shows the even greater output levels drop off  of the TG notes
49 to 91 and the TG output curve  of this 1956 B3 after it was recapped
with Goff caps shows the output levels of the TG notes 49 to 91 now
restored and closer to what the output levels were like when this B3 was
new.. 
 
>But then I noticed that  "Jurgen's 1959 B3" with wax caps also displays
a curve much like a mylar capped   model. 
 
The  wax capped Jurgen's 1959 B3 has  very strange output levels in the
TG notes 49 to 91 range with strong outputs in the TG notes 49 to 61 and
then a big drop off in the  TG notes 62 to 74 range  and then  some very
strong and uneven  levels in the TG notes 75 to 90 range. This TG seems
to have been sloppily calibrated and considering that this is a wax
capped organ I imagine that it would have been a very shrill and bright
sounding organ when it was new . Although the TG curve of this 1959 B3
is strange looking , it is possible that it might be  a very distinctive
sounding organ with a good sound.
 
> Why would some organs break the mold?  Could differences in storage
conditions or how much they were played affect the >aging rate of the
caps?
 
I have read that wax capped organs stored in warm and very dry
environments have wax capacitors with noticeably less deterioration due
to age. Earlier this year I was given a wax capped 1963 L-102 organ that
was from a church and the levels of the TG notes 49 to 91 are similar to
the 1972 TG output readings of the wax capped Mihevic 1956 B3.  
  
 
> 2.This is clearly a "your tastes may vary" situation. Some of the
organs that were 
>described (presumably by their owners) as bright-sounding showed curves
that would 
>suggest they're pretty dull-sounding.  And some of the organs that
looked like they might 
>be very bright based on their curves were described as mellow. 
 
This could be personal taste matter or it could be because of the sound
of the organ preamp ,the Leslie or the tone cabinet or the actual
speakers. Another possible factor might be the tolerances of the
particular manual tapering resistance wire ohms values in the manuals.
In my TG spreadsheet there is the TG output curve of a red mylar capped
1966 C3 called 
"Bernie's Musicland 1966 C3" that I measured in an organ shop in 2005.
This 1966 C3 has normal stock output levels in the TG notes 1 to 48
range but it has uneven outputs in the TG notes 49 to 91 range  and the
TG notes 85 to 91 are set higher than normal  but this C3 actually
sounded very nice with a distinctive sound and it had a nice shimmery,
airy leakage sound.  This C3 also sounded similar to the New B3 that was
in the shop. After I came home from the shop I recalibrated the TG notes
49 to 91 of my own recapped 1962 C3  to have identical output levels as
the very nice sounding 1966 C3 in the shop but after I played my C3 with
this identical calibration, my C3 sounded thin and shrill so therefore I
had to again recalibrate the TG notes 49 to 91  back down to normal
levels.  I am not sure  if the 1966 C3 in the shop sounded better
because of the  manual tapering resistance wire ohms values or because
of the AO28 preamp and the Leslie 122 or the Jensen V21 in the Leslie
122 that it was connected to in the shop.   
 
   
   
>3 While the mylar capped organs tended to have similar shaped curves,
there still was 
>quite a bit of variation among them - including notes here and there
whose outputs were 
>significantly above or below neighboring notes.
 
I have some experience with recalibrating the TG and it is very time
consuming  setting each pickup  rod to produce an exact desired output
level because there is a very small space of movement  for the pickup
rods and even tightening the set screw often causes  the pickup rod to
move slightly thus changing the output level especially with the treble
TG notes and I have to untighten the set screw and again reset the
pickup rod to produce the desired output level. Because this is so time
consuming I don't think that the  Hammond employees would have been
allowed to spend this much time being finicky with  the output levels of
each TG note so I assume that the TG pickups set to produce output
levels near enough to the factory standard output levels chart was
considered good enough when the employees calibrated the TG's at the
factory  so therefore each TG has  slightly different output levels
especially in the treble TG notes where the pickup rods are especially
sensitive to even the slightest micro movement caused by the set  screws
being tightened.
 
Another thing that I noticed when recalibrating the TG is that the tone
wheels move  slightly side to side. Because the front edge of the pickup
rods of the bass and the midrange TG notes are wider , the slight side
to side movement of the tone wheels does not affect the output levels
but the front edges of the pickup rods of the upper midrange and the
treble TG notes are much narrower and consequently the slight side to
side  movement of the tone wheels can noticeably affect the output
levels . Even pushing the TG whilst it is mounted on it's support
springs causes the output levels  to change and this is a real nuisance
when I am recalibrating the TG to have a smooth , even  output curve.
The output level variations caused by the slight side to side movement
of the tone wheels is one reason for the variation in the output levels
from one TG  note to another . With the TG output curves that I have
most of the  variations and unevenness are in the upper midrange and
treble  TG notes.    
 
 
>The conventional wisdom is that the mylars don't drift in value. Is it
possible that they only drift far less than the wax caps?
 
In late 2005 I did some  work on a 1970 T-300 before selling it and I
measured the red mylar capacitors and they all measured at within 5 % of
their  nominal 0.255 mfd and 0.1 mfd values so therefore these
particular red mylar capacitors are still at or very close to their
original mfd values. This means that they are still properly matched to
the filter inductor coils and because of this I took out this  red mylar
capacitors tray from the T-300 and I put it into the TG of  my own
recapped 1962 C3 and I then put the recapped capacitors tray originally
from my 1962 C3 into the  TG of the 1970 T-300 before selling it.  I do
not know  if  the red mylar capacitors will eventually begin to drift
off spec with age .  
 
 
> Or is this variation likely due to inconsistent processes (or
components) used during 
>initial assembly?
 
As I explained further above , calibrating the whole TG to exact desired
output levels is a very finicky and delicate task requiring patience so
therefore this might  be a reason why each TG has different variation in
the output levels and it is possible that some  TG's were calibrated
sloppily at the factory and they escaped the notice of the factory
Quality Assurance inspectors.  
All the best.
Kon