Re: Tech Talk- Leslie snapping

[GOFFProf@aol.com]

One of our board members (thanks Dan!) suggested a source of AC suppression
caps from DIGI-KEY as a replacement for the original 600vdc black or orange
capacitors in Leslie amps.  I wanted to share my experience on these and
similar component "upgrades".

We tested these same caps and other similar ones last year as a possible
less-expensive replacement of the early "black cat" and light green
"greenies", or the current orange, bulky and expensive "orange drop" caps.
 The new caps worked for a few months, and then simply committed suicide and
died.  As Murphey's Law would dictate, one of my "test amp" failures was in a
Leslie 122 amp for Hall & Oates.  Needless to say, two months after
rebuilding, when the Leslie started snapping and crackling loudly in the
middle of a show, H&O organist Bob Mayo, their keyboard tech (Pete Moshay)
and  I were not happy with the "new" replacements.  Since it was a test amp,
we supplied Pete with a fresh set of .1uf - 600vdc Orange Drops as a
contingency.  Pete simply replacements the caps with the orange drops ---
back in business.  The same amp has performed flawlessly since then. 

SO, after similar failures in our rental and test amps (NO mail-order amps
were retrofitted with the new caps) it was back to the tried-'n-true orange
drops, battle-ship-beefy as they are.  HAMMOND also tried some 150VAC rated
suppression caps in the late 80's. They were an odd light blue color and
lasted about as long as the newest "replacement" did.  If you happen to have
them in ANY of your later-model Leslie 122 and 147 "gold" colored amps, get
them out!  They are mounted in the upper-left corner on the AC outlets. 
Carefully cut them out when new replacements are in-hand, and replace them
one-at-a-time.

I personally believe that the new capacitors cannot take the abuse of
continued high voltage/ current peaks and rapid charge-discharge rates, which
are the result of switching the Leslie a few times.  Think about how MANY
times you switch speeds in ONE night at a gig.  Then over the weeks and
months, years....

American technology may sometimes be a little old and bulky, but it works.

Replacement TONEWHEEL GENERATOR FILTER CAPACITOR 

"Lion & Tigers & Bears --- Oh MY!"

When we were testing every imaginable type of capacitor as a replacement for
the original early-HAMMOND (pre-1963) wax-type and later (post-1963)
styrene-type tonewheel generator filter capacitors, we tested each probable
candidate in test organs.  Although each capacitor manufacturer claimed that
their design was equal-to-or-better than the originals, almost all failed our
descriminating tests miserably.  

Most new capacitors are now primarily designed to block DC voltage, and their
general application is NOT audio. The primary need in a HAMMOND tonewheel
generator is for accurate and consistent filtering of very-low level audio,
although a good DC performance is necessary especially on organs with
percussion. The actual "filtering" operation is intended to block or remove
as much of the lower frequency cross-talk and other noise from the tonewheel
being filtered.  Some new (and expensive!) types of capacitors altered the
tonewheel output to such an extent that the resulting sound was almost
unusable.  Others filtered the audio, but were so naturally inductive that
they picked up 60hz hum like a sponge and introduced it into the tonewheel
audio.  In these types of capacitors, since they ALL did it, the organ sat
there and HUMMED loudly when several keys were pressed.  Unbelievable.....

My final choice was a capacitor which not only exhibits the critical audio
filtering required in the generator's low frequency (almost DC) 32hz to
6000hz narrow band of frequencies, but is also completely non-inductive, and
impervious to oil saturation.  I carefully select, test and hand-match them
in groups in much the same way HAMMOND originally did.  But I also sweep
audio through each cap and "tweak" the match even further to make the
resulting sets of filter capacitors much-closer in tolerance than the
originals.  I still reject over half of the new capacitors from the factory
as unsuitable for use in our Tonewheel Generators Filter Capacitor Kits!
 These are returned (for resale to....) or resold to another firm for use in
a non-audio application. 

Bottom Line - When considering ANY component replacement, there are many
factors to consider, and price, in MOST cases is NOT the most important one!
 We test all of our equipment and kits to FAILURE so we know what will happen
to them in your equipment on the road, in the studio, or at home!  

Capacitors & Resistor & Diodes... Oh my!

Al Goff, GOFF Professional via AOL