Assitance with Leslie 147 Circuit And Related

[keithb7]

Hi, A friend of my mine asked if I would take a look at his 1967 Leslie 147 cabinet. His complaint is general intermittent crackling noises. I have some considerable guitar tube amp maintenance & repair experience, so I agreed to take a look and poke around. I have never worked on a Leslie before, and I am learning as I go. I'll have some questions and I am hoping there is some experience here to coach me along at times. Here are a few pics.

More info and questions to come. This post is more of a project introduction to learn if there are folks here that are able to help with my inquiries. If you're reading this and interested please check in. I will post some more questions and my findings. Much appreciated. Thanks, Keith





Some of my questions may be to satisfy my craving for understanding of the circuit. I learned that a power amp is required in front of the Leslie. In this example the owner has been using an old Kustom solid state amp. The amp has been modified with the large round 6 pin socket to send signal and AC line power to the leslie chassis. Here is a pic of the Kustom amp for reference and future questions. The modified socket in on the rear, top right corner in the pic.

[Enzo]

The amp in the Leslie IS a power amp.

Amp makes noises? Same as any other amp, tubes, connections, etc. Also there is a heavy cable from the Leslie to the organ. The connections in the end plugs can get loose, and so on, so don;t overlook the cable.

[keithb7]

The amp in the Leslie IS a power amp.

Amp makes noises? Same as any other amp, tubes, connections, etc. Also there is a heavy cable from the Leslie to the organ. The connections in the end plugs can get loose, and so on, so don;t overlook the cable.

I pulled the chassis to go over the circuit. I found a few components quite out of spec. I ordered parts including replacements for all e-caps. Enzo you were pretty bang-on with the cord suggestion. The crackle wasn't the cord, but a wire from the back of the large connector, for the cord, that went to the AC fast/slow switch inside the chassis. It was pushed into a socket and never soldered. Someone was in this amp some time ago and really should have stayed out of it. They did some poor maintenance. Tonight I removed 8 twist caps (marrets?) and hard soldered the connections and covered with heat-shrink. They should be fine now for another 50 years or more.

The owner asked if I could hook up a footswitch to control the fast/slow motor speed. I am unsure how to do this safely and properly. The switch in the Kustom amp head, controls 120V AC to select fast or slow. I am not keen on running 120V out to a footswitch on the floor and back to the head. I was thinking a relay would work maybe so I have low voltage running out to the footswitch and back.

Could I use the heater circuit at 6.3V AC? Tap into that and run it to a relay to switch on/off the 120V for the speed control. Is that safer? Or maybe there is a better way? Any help is appreciated. The circuit is attached. You can see the 120V fast/slow selector near the phase inverter.

Thanks, Keith

[Brad1]

Some of my questions may be to satisfy my craving for understanding of the circuit. I learned that a power amp is required in front of the Leslie. In this example the owner has been using an old Kustom solid state amp. The amp has been modified with the large round 6 pin socket to send signal and AC line power to the leslie chassis. Here is a pic of the Kustom amp for reference and future questions. The modified socket in on the rear, top right corner in the pic.

A few observations:

It might be interesting to look inside that Kustom amp to see from where the signal comes that is fed into the Leslie? The Leslie needs fed from a PREAMP, NOT a power amp. Like this: http://www.captain-foldback.com/Lesl...bo_preamps.htm

As mentioned, the Leslie amp IS a "power amp".

Did the tinkerer tap out the preamp section of the Kustom, or is that thing feeding it full output power, basically, paralleled from the speaker jacks?

Full power out into Leslie amp input just might not be the best thing for EITHER units? Wonder what the load looks like on the Kustom output (if connected to power amp out)? Wonder how much the Leslie input is being way too overdriven (if connected to power amp out)?

I'd check that out!

Also, the Leslie is powered THROUGH the Kustom amp's AC input? From where? Directly off the AC input line? After a fuse/power switch in the Kustom amp? That Leslie amp draws a lot more current than that Kustom will. Can everything handle that? Can even the Kustom AC cord handle what it was designed for, PLUS much more current drawn through to power the Leslie? I'm doubting that rig is 'UL- or CE-approved', at all!

And, then, he has that 120V 'motor speed control' connected to a toggle switch mounted on the front of the Kustom? ALL that is running through an umbilical from the Kustom to the Leslie...using...what cord?

Sorry...but to me, anyway, NONE of that looks like a good idea. For what the Kustom is (was?) worth, cost of the questionable work already done, and cost at this point...he'd have been better off just paying $300-$400 for a properly-designed for that unit controller/interface that he could just plug in and go?

I think I would advise against using that funky rig, at all. But, that's just me.

Brad1

[52 Bill]

Brad is correct with a lot of his points. Please check and see what was done inside the Kustom head.

It this being used for guitar or organ?

The fast/slow motors are normally controlled by a relay inside of the Leslie. What voltage is being used to drive the relay? Where is it being generated?

[keithb7]

I will try to answer your questions. Someone modified the Kustom amp. Not sure who, or how long ago.

The fast/slow motors are controlled by a relay inside the Lelie. However you need to switch a separate 120V AC off and on to activate the relay in the Leslie.

There is a large 6 pin heavy duty cable that runs from the Kustom head down to the Leslie. Not sure what the trade name is for the plug. I am pretty sure this is the original cable that would have been used on a stock Hammond organ with a Leslie.

The signal from the head to the Leslie, was pulled right off the speaker jack on the rear of the Kustom. Not ideal for sure as this is not a pre-amp signal. This is a powered, amplified signal.

The 120V AC power to the Leslie chassis transformer is pulled from the Kustom amp's on/off power switch. The power wires are joined at the main on/off switch in the Kustom amp. This is before the main power fuse for the amp. The Leslie has its own main AC power fuse. All pretty sketchy for sure 120V/15A is going through this heavy duty power cable to the Leslie.

The owner uses this set up with an electronic modern keyboard. I agreed to look at just the Leslie as my solid state knowledge is very limited. In the Kustom I was thinking at least the death cap off the power supply and the non-gounded plug should go. I am planning to add the grounded plug here. Owner asked if I could replace the fast/slow switch, located in the Kustom head, with a foot controlled switch. I am beginning to think I'll just stay away from this request. Seems a little to sketchy the way things are wired up. I'd rather not get involved.

[g1]

I don't think a 120V relay would be stock. This thing sounds like an accident waiting to happen.
I would recommend you go with your gut and not get involved, unless the owner wants to restore it to original with the proper combo preamp.

[52 Bill]

Yes, the 6-pin plug and cable set are the original Leslie type connectors. As long as they are in good repair, they will be fine to use.

You can change the relay that is located inside the Leslie chassis for one that is controlled by a lower voltage, which would allow for a footswitch system without running 120 volts ac through the cables. The Kustom will have 40 volts dc and 8 volt dc power supplies. You could also create a separate relay supply on your own.

I would replace the Kustom power cable with a heavy duty three wire one and remove the ac ground cap. The cable should be picked to carry the current for the Kustom and for the Leslie power amp.

The signal coming from the power amp output of the Kustom could be too hot for the input of the Leslie, but if it has been working like this so far, the owner must know how high he can turn up the amp without overdriving the Leslie input.

The alternative would be to wire the output from the Kustom directly to the Leslie speakers, bypassing the internal power amp.

[Enzo]

The fast and slow motors are 120v, and plug into common outlets on the amp. The original relay should be 120v, but could be changed to anything. There is already 120vAC coming down the umbilical, two more wires of it wouldn't be any less safe. The switches on the organ console had 120v inside.

There were some models that sent 300v DC down a balanced audio line to control the relay.

[Brad1]

The alternative would be to wire the output from the Kustom directly to the Leslie speakers, bypassing the internal power amp.

If that was a SS Leslie, that would be fine. But, it's a tube Leslie. The Leslie amp needs a load. I have modified a couple Leslie 825s (SS amp) to work as intended, or speakers plugged into an external amp, and also an on/off, fast/slow footswitch. Worked great. Much more difficulty in this one.

So, he COULD just power from the Kustom direct to speaker...as long as he put some kind of load on the Leslie amp output?

Brad1

[Enzo]

If he does that, why keep the Leslie amp at all? SImple switching can be wired direct to the motors. Or keep the Leslie amp for the motor outlets, and just yank the power tubes.

[Leo_Gnardo]

If he does that, why keep the Leslie amp at all? SImple switching can be wired direct to the motors. Or keep the Leslie amp for the motor outlets, and just yank the power tubes.

I'm liking that idea Enzo, and I'll expand a little: sell the Leslie amp off to someone who wants it and substitute a tin box with a 6 pin connector and 4 AC outlets for the motors plus a jack for the speakers. Simple, cheap, and $$ in the pocket once all is said and done. Will remove some weight from the Leslie in the bargain, make it a little less of a pain in the a...., I mean back to move.

[52 Bill]

So, he COULD just power from the Kustom direct to speaker...as long as he put some kind of load on the Leslie amp output?

No, my thought was as Enzo described, disable the power amp entirely and just use the speakers.