HL 722 switches Off after a whiles.

[Tastenheld]

Hi all.
I have a Leslie HL-722. It works as should with my Viscount Legend, but, espevcially on higher volume it suddenly turns off. Looks like a heat problem, as I can switch it on after a few minuteas of waiting.
Where can I Look? Does someone have an idea?

Regards,
Sven

[muckelroy]

When you say it turns off, do the motors also stop spinning?

The 11 pin Leslie speakers have a power-on circuit, so that is where I'd focus my attention. How do you power on the Leslie? Is there anything connecting in between the organ and Leslie such as a preamp pedal, or does the Viscount Legend control whether the Leslie powers on or not? Is the connector / cable loose on either side? Have you tried a different known-good cable?

I do not think that there is anything in the Leslie that is designed to automatically shut down the Leslie if it overheats. There are fuses which might blow, however if that was occurring you could not then power it on again.

[muckelroy]

When you say it turns off, do the motors also stop spinning?

The 11 pin Leslie speakers have a power-on circuit, so that is where I'd focus my attention. How do you power on the Leslie? Is there anything connecting in between the organ and Leslie such as a preamp pedal, or does the Viscount Legend control whether the Leslie powers on or not? Is the connector / cable loose on either side? Have you tried a different known-good cable?

I do not think that there is anything in the Leslie that is designed to automatically shut down the Leslie if it overheats. There are fuses which might blow, however if that was occurring you could not then power it on again.

[Tastenheld]

Hi and thanks for your reply.

Well, both amps and motors turn off. The Leslie is completly powerd off.

The cable works fine on a 760 with adapter and I messured it.

I have nothing between organ and leslie.
Leslie ist permanently connected to AC source and Legend. If I turn on the Legend, the HL-722 powers up. All speakers are active, chorale, stop, tremolo are working.

I don't think that the Leslie has protective circuits, as far as I understand the schematics.

I wonder If there ist an electronic part that might overheat due to a too hot Input and then causes the whole system to fail..

[muckelroy]

I need more information about how it behaves. When you say “hot”, is that only talking about the volume of the instrument input? And when this happens, does the Leslie automatically turn back on by itself if you just wait a few minutes?

If that is what is going on, I would take measurements of the power-on section of the Leslie amp, when the issue occurs, paying close attention to the state of the relay and triac of that circuit.

What is supposed to happen is that connecting pins 6 to 5 turns the Leslie on. It’s entirely possible that something is happening with the Viscount Legend that this connection is being interrupted, or that ground is beginning to float at higher volumes. It would help, as with any isolation, to test this Leslie on a different organ if possible to see if it does the same thing or not.

If this amp hasn’t been rebuilt in its lifetime, it’ll need that either way.

[Tastenheld]

Hi muckelroy.

Yes, with "hot" I meant a high organ-output/ high Input-level at the Leslie.

But, you were on the right track. I replugged the 11-pin cable today after testing my 760 yesterday.
And when I switched to fast, the Leslie switched of, switching back to slow, it woke up again. So there seems to be slack joint either in the cables plug or the amps connector. I pressed it a bit harder, and the problem was gone.

Thanks for your ideas. I will take a closer Look into this alter.

[Tastenheld]

Well, seems like it has fleas and lice at the same time 😂

Went off after a while, when I was not switching slow/fast.
I left the organ on and after a while the Leslie started up again.

So, I think there ist one component in the power on section getting too warm and causing tob switch off the Leslie.

[muckelroy]

The power-on circuit is not that complicated. There is a small power transformer (T2) that gives power to a few diodes, a triac, which read voltage drop on pin 6. When pin 6 gets current flowing through it via connection to common (pin 5,) the power-on relay closes, which lets the amp power transformer T1 get power, turning the rest of the Leslie on. So you must find out what that relay is doing when the issue occurs. If the relay is open, maybe the relay is faulty and needs replacement. If the relay is closed, then your problem lies deeper and will need more investigation.