Leslie Project

[keithb7]

I hope I am ok to post this thread here. I was asked to take a look at a local musician's Leslie cabinet. It is tube powered somehow. I have never worked on one before, let alone actually play through a Leslie.

I don't quite have a grasp on its function yet. I will be studying as I go through this.

As of this writing I do not know the year. I am sure we will find clues to help get a fairly close date.
Owner says it is a Leslie 147 from the 60's. I found a schematic on the side of the circuit chassis. It indeed reads "Leslie 147". The C15 Jensen speaker code reads 220742. 42nd week of 1967? Likely.

I'll dig up a schematic and study it a bit.

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From what I see so far, it appears that the AC power for the Leslie comes from the organ or amp driving it. In this case, the Leslie owner has a Kustom Solid State amp head. It appears to have been modified to work with this leslie. It has a large round 6 pin socket in the rear of the amp, that I see is indeed wired to the Kustom amp's power switch.

Kustom amp seen here:

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Round socket plug for leslie seen below here, top right corner:

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Tubes in this amp appear original and are Leslie brand or RCA. I have not yet figured out how to pull this chassis. The rear 2 mounting screws may have to be pulled blindly?

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More to come as I progress.

 

[keithb7]

Unsure why first two pics are not showing. Here they are again:

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[keithb7]

Edit:

Links are working this morning.

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[moosie]

Popcorn...

 

[xafinity]

Weird. Hmm. Here's a link to the photo album:

(link removed)

Quit fooling with those photo albums and just drop the j
Jpegs directly into your post

 

[xafinity]

Quit fooling with those photo albums and just drop the j
Jpegs directly into your post
View attachment 537763

I love those old Leslie's with an old B3

 

[schmee]

You still haven't told us what you are trying to do or fix.

 

[wanderin kind]

you need the Fender Vibratone. Lucinda William's guitar player was just in here, well, about a year ago, and bought one.

 

[keithb7]

You still haven't told us what you are trying to do or fix.

The customer complaint is general intermittent crackling. I was asked to check circuit component values and voltages versus spec. Perform a cap job. Remove fast/slow switch on the Kustom head and replace with a jack that allows control with a footswitch. It'll be slow progress as I put in a little time each evening. I'm questioning myself why I took on this job right now as I am juggling a lot of work around the house. Oh, I remember why now, because owner said I was recommended by a few repeat customers. Hard to let people down.

More info will trickle out as I get into this Leslie further.

 

[schmee]

I've repaired a couple for my buddy who has 4 now I think... and 5 B3's! Of course the tubes could be the crackling. One died and it turned out to the rectifier diodes.. strange as that doesn't seem to happen much. I replaced them all. Good schems and info on Capn Foldback's site.

 

[Hobs]

You don't have to pull the rear screws. There's a bracket and a flat hook at the back. Remove the front center screw, then pull straight forward. Easy.

 

[keithb7]

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[keithb7]

 

[moosie]

Sounds fantastic!

Footswitch to a relay, eh? Interesting. What's the circuit behind the switch look like?

Not exactly related, but the relay idea made me think of Neil Young and his 'whizzer'.

 

[Snfoilhat]

Nice!
I built a Leslie 16/Fender Vibratone type cabinet from an organ's internal Leslie baffle/rotor/motor/speaker assembly, and kicked around a few (bad) ideas for an outboard speed control. I'd also be interested in seeing how this is wired up. Thanks!

 

[FenderLover]

So, the Kustom drives the Leslie and controls the speed, what does the chassis on the bottom of the cabinet do?

 

[keithb7]

This whole set up is new to me. So I may not have the facts right, but what I see here is this:

The Leslie chassis has a tube amplifier, as well as a switching device built into it. The main power tubes are 6550 tubes, a pair of 'em. There is a 12AU7 phase inverter and solid state diode rectification. However there is 1 tube that's sole task is a power regulator. There is a 120V switch in the chassis that sets fast or slow speed of the motors that spin the tweeters and the directional scoop under the 15" woofer. This 120V switch is seen in the chassis pic above left of and adjacent to the .1uf green cap. Top right area of the photo.

As far as I can tell, the Kustom is donating a pre-amp signal to the Leslie cab. A heavy duty thick cable connects at the back of the modified Kustom amp that delivers ground, signal, 120V AC mains power, and 120V AC power to the fast/slow switch. The cable connections inside the Kustom go to ground, to the line signal and right off the 120V main power supply. Likely all this would have been much each when you just plugged the Leslie into a Hammond organ that it was designed to be used with. The Leslie cab can do little to nothing on its own. You can't plug a guitar for example directly into it without some type of pre-amp (I think). Anyone feel free to correct me.

When I cycle the fast/slow switch on the face plate of the modified Kustom amp, I am allowing or blocking the secondary 120V AC current to go to that fast/slow switch in the Leslie chassis.

The chassis in the Leslie cab has an ohm load switch for 8 ohm or 16 ohms. Also a volume, which you can crank and get "Born To Be Wild" overdriven organ.

 

[keithb7]

Nice!
I kicked around a few (bad) ideas for an outboard speed control. I'd also be interested in seeing how this is wired up. Thanks!

Here is a quick illustration of what I was thinking about trying for an outboard speed control. Use a typical hammond smaller chassis box, like used in so many guitar pedals. Install a Carling typical on/off footswitch. Run 9V DC pedal power supply to it. Then run it to a relay inside the Kustom amp that turns off and on 120V AC to the hi/low speed motor inside the Leslie. Sorry about the chicken scratch. Its a crude sketch to illustrate my idea. It is not complete nor accurate but gets the point across I think.

I am open to improvements. Ideas. Or just call me plain dumb. - K

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[moosie]

I'm struggling with why a simple fast/slow switch inside the kustom is wall voltage. I know nothing, but that just seems odd. Before hacking up a relay, perhaps explore if the switching circuit is itself a poor hack, that could be done an easier way / lower voltage / ground shorted footswitch. Does that make any sense at all?

 

[keithb7]

See the trem fast/slow here in the schematic. Just below the 12AU7. I called this 12AU7 a PI. Actually no, I think it is a pre-amp. No?