RT3 to Leslie 251 Connection

[Daniel Klein]

Hello! I'm helping out with getting an RT3 that I used to play on hooked up to a Leslie 251 for a producer friend's studio.

I can get some sound out of the Leslie using the 6 pin cable I bought on ebay, but it distorted and weak. The Hammond has a silver Leslie connector box in it that's labeled for 122, etc. Is the problem that we need a different connector box, a different pin-out configuration, have tube problems at the Leslie, or...?

Also, the half moon switch is not controlling the leslie, so I'm assuming it's the connector box.

Thanks in advance for anyone who can shed light. I also have a call in to Bill Axeman of Alltek here in LA who has worked on this RT3 for me before.

[JoeyB3]

A 122 style Leslie is not wired the same as a 251 (balanced vs. unbalanced/DC switching vs AC switching, etc)...so you will need to re-configure.

Go to this website and download the 251 manual. There will be info in there on how to properly connect to your RT3.
http://www.captain-foldback.com/

[muckelroy]

Do not ever attach a 122 type hookup to a Leslie different than that specified for the 6-H hookup. See this guide: http://www.dairiki.org/HammondWiki/LesliePinouts
If you proceed down the path you are currently taking, you are slamming your amp with DC voltage at the signal pins. Furthermore, if you adapt your organ for a 6-W hookup and connect it without modifying your amp, you are slamming AC voltage to the secondary channel of your 251 amp.

The Leslie 251 is a 6C type hookup. The idea of this hookup is that a dry channel, and a reverb channel are sent to the 251.
-- That said, one option is to make a 6-C type hookup on your organ, but that doesn't make sense, because you don't have a reverb amp on your RT-3. I suppose you could send dry signal to both channels if you really wanted to, but you'd have 2 stationary speakers on the 251, the purpose of which is to put out reverb signal, not dry signal.

So most likely, what you want is to send dry signal only to the 251, and send nothing to the secondary (stationary) channel. Doing that requires 3 things:

1.) Add a 6-W hookup to your RT-3.
2.) On the 251 amp, disconnect the wire that runs from pin 5 to the middle 12AU7 grid and tap it off.
3.) Move the tremolo relay coil wire and .1uf capacitor lead attached to 251 amp pin 4, to pin 5. (Leave the AC Mains PT wire attached to pin 4 as-is.)

From there, you may remove the 6973 tubes from the Leslie amp, and disconnect the secondary channel speaker plug from the amp. However, the power supply won't behave like a 147 amp without some modifications to the amp, such as replacing the 125 ohm 10 watt resistor with a 150 ohm 10 watt resistor, as well as replacing the 150 ohm screen resistor on the OC3 with a 470 ohm.

The 251's 6550 output section has no negative feedback loop like the 147 type amps do, and is wired up similarly to how the 122 amps are.... I could go on, but I'll stop talking. Hope you understand the amount of work required here.

It may be best, in this case, to find a 122 amp which is what your organ is already wired for and needs.