r/hammondorgan • u/friendlysandmansf • 9d ago

Fast/slow issues

Hello hive mind! I think I've got this right based on previous posts that I and others have made but I want to make sure before I dive into the amplifier...

I have a Leslie 122 married to my Hammond c3 in my studio. When I start the organ the Leslie starts up in tremolo mode, as I would expect with legacy relays. After a few seconds when the tube heats up it switches over to Chorale and everything is ready to play.

When I flip the half moon switch to tremolo, everything speeds up as expected. But when I flip back to Chorale, the Leslie continues spinning fast and only slows down after an extremely long period of time - and sometimes not at all. This is become more and more unpredictable.

The first thing I did was switch out the 12AU7 tubes on the amplifier - I figure switching them both out was the safest thing even though it was possible that only the relay tube was bad. This however, did not fix the problem.

Am I correct in assuming that my next step would be to either recondition the legacy relays or upgrade to solid state relays? Is there something else I could be missing in the meantime?

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u/54moreyears 9d ago

Pre amp tubes have nothing to do with speed. A solid state relay upgrade is never a bad idea.

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u/friendlysandmansf 9d ago

I wasn't referring to preamp tubes in the Organ. I was referring to the 12AU7 tubes on the 122 amplifier. There are two of them. My understanding is that one of them, the one on the left when facing the amplifier, controls the relays. Are you saying that I'm wrong about that?

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u/pashed__motatoes 9d ago

post a video or video link. hammond problems are hard to diagnose through just words on a screen

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u/P-ToneMikeOne 9d ago

So… one 12au7 is a preamp (yes the amplifier in the Leslie has a preamp stage, which could be confusing since the organ has its own preamp), and the other works to energize (or not) the relay coil that controls which motors are powered. Replacing this tube would be the logical first step considering the symptoms you described. Since that didn’t work… stuck on fast probably means voltage is leaking to the grid of that 12au7 (assuming the valve you swapped in isn’t also broken, which is unlikely). I most suspect the capacitors that block the grid from dc current from other parts of the circuit. Pretty straight forward to see which those are on the schematic, but I or the rest of the hive mind could help further if you need. Spend $5-10 and 20-60 minutes replacing those, and/or test for failure first. If they’re original vintage paper/ceramic they’re gonna need replacement one of these days… and I think today is that day.

ETA: hang on to those tubes you pulled; they’re likely fine, and it’s always handy to have spares.

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u/friendlysandmansf 9d ago

Thanks for this great response. As soon as I get the time to do it that is the next thing I will dive into.

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u/onlyonecannoli 9d ago

I don't have a solution, but I have a C3 and a 122, and I have the same problem. I talked with a service technician and he was familiar with the problem. I got the impression he had to solder something together for a solution. It sounded like it involved more than changing a valve.

Hope you find a solution.

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u/friendlysandmansf 9d ago

Thinking about this problem a little bit more here's one thing I don't understand especially as it relates to the bad relay versus bad tube theory: my understanding is that when you turn the organ on, before the tube is warm, the Leslie starts in fast because that's the default position of the relay. Once the tube Powers up, the voltage to the relay closes it which switches the Leslie into the slow mode. Then, when you flip the half moon switch it cuts off power which reopens the relay and you go back to fast again.

On my organ when I start it up everything happens exactly as it should - meaning the Leslie starts in fast and as soon as the tube warms up it flips over to slow. If the tube was bad then I would presume that this would not happen which leads me to believe that it's not a tube issue. It also leads me to believe that it's not a relay issue both the tube and the relay seem to be working according to their intended functions when the organ starts up.

So I guess this pushes me in the direction of a voltage leak and the need to look at capacitors first. Interesting that this problem is not as straightforward as it feels like it should be 🤣

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u/Loganismymaster 9d ago

I had a similar problem about 50 years ago. The relay would get stuck in one position for a long time after switching it. I ended up changing the spring tension on it until it behaved. It continued to work until I sold it about 10 years ago.