Re: combo preamp / 122

["Todd A. Phipps" <b3nut@madison.tdsnet.com>]

>On a 122 pins 2 and 5 are ground and B+.  THe B+ serves two purposes one 
>to supply the DC nessasary for speed switching (Which is piggybacked on 
>th audio line) and if the hammond is an A,AB,C,D,G,E,BV,CV,BC,B2,C2,RT, 
>or RT2 it supplies the nessasary DC for the preamp to work.  Latter 
>madels like your A100 (B3) had a full power supply built in, but early 
>console preamps had only the filament supply (6.3 vac) built in and were 
>intended to recieve the high voltage B+ from the tone cabinet (Hammond or 
>Leslie) (BTW: B+ is around 400vdc or so)

The B-2, C-2, and RT-2 have a power supply built in, using a 6X5 
octal-base rectifier.  The xV-series consoles were the last to require 
external B+ supply.  I wonder if Hammond originally did it that way to 
cut power supply costs or to thwart Don Leslie?  But all consoles having 
selective (great/swell) vibrato contain a power supply while prior 
consoles like the A, B, C, D, BV, BC, BCV, CV, DV, G, E, and RT required 
the B+ feed from the power cabinet.

I had a bedraggled CV once, it sounded OK until the preamp died. I used a 
D-20 to give the organ its juice but ran the audio to my 145.  I hated 
the swell rheostat with a passion because of the zipper noise. BTW I have 
some parts left over from the late CV including a tone generator (the TG 
is in decent shape) if anyone's interested.

HTH

TP


------------------------------------------------------------------------
Todd A. Phipps and his silly dog Obie
Board of Directors, the Michigan American Pit Bull Terrier Club, Inc. 
(UKC)
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Internet: b3nut@madison.tdsnet.com
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