Re: 251 to 122

[dlkerl@elvis.b11.ingr.com (Dan Kerl)]

The Leslie 251 was designed for Hammond organs with built-in amps and
reverb units (A-100, M-100 series).

The 251 amp rotary channel is almost identical to a 147, which has an
unbalanced input.  A caveat: Make sure the cathode resistor for the
output tubes is 150 ohms instead of 120 ohms. Mine originally had a
120ohm resistor (it was in the Leslie schematic), which results in over
100mA quiescent current in each 6550.  This results in reddening of the
plates, shortened tube life and more stress on the transformers.  I
added series resistance (27ohm/2W) to bring it up to around 150 ohms,
which is what a 147 amp uses.  The tubes are happy.  (BTW, the Svetlana
6550Bs that Goff sells are excellent. The amp really screams)

The stationary channel is like the reverb channel in a 147RV, but lacks
the reverb tank and driving circuitry. The signal travels down the cable
on a dedicated wire. Unless you have an external reverberation unit, you
probably won't get any use out of the stationary channel. You might be
able to pull the tubes associated with the stationary channel, which
would take some stress off of the power transformer.

I think Al Goff's company does amp conversions (147 to 122, etc.). You
might also be able to trade the amp.  However, if a 147 is acceptable to
you, the 251 amp should work just as well.  You would connect the rotary
channel to the Hammond in the same fashion as as you would a 147
(whatever that requires)  Good luck.

                                                Dan Kerl
                                                dlkerl@ingr.com