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Resurrecting the leslie (just bought a project)


Pale

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Hey guys, I just bought a leslie 760, for 200. Considering the prices people are asking for a leslie today I think it was a bargain. Drove 300km round trip to get it, we met half way on a gas station. I couldn't try it out, but I decided to risk it at that price so I took it.

 

This afternoon I took it to my rehearsal space, and after figuring that it doesn't work properly (some crackling, no sound coming out) I decided to open it up and see what's wrong. The leslie is not in great shape, but I'll make it work (if you help me out a bit). I armed myself with screwdrivers, voltmeter, soldering iron and I went inside.

So this is what I've figured out so far.

 

Previous owner, who sold it to me, did some tampering with the leslie:

 

-there's a leslie II preamp wired inside the leslie! So I actually got a preamp pedal as a bonus (though without the casing and the 9 pin cable).

 

-he didn't know how to wire it up properly, somehow he conneted the on/off regulation of the motors by swithcing the power supply directly. He also made his own footswitch. Good thing I double checked the voltages on everything before touching anything - the guy had his DIY footswitch (the metal switching part) on 220V! Try to play barefoot on that baby and adios amigos.

 

-I didn't get the 9 pin cable, but everything is connected inside (leslie and preamp) and leslie now takes 3 regular jacks.

 

-the leslie powers up

 

-I decided to take the plunge and use his deathtrap "220V on the switch" footswitch (rubber soles ftw). It actually works, and both motors switch speeds. Too bad it's a life hazard, I'll have to rewire it.

 

-found a source of crackling, resoldered the connection and solved the problem. I also (finally) got the sound out of it.

 

-both speakers work

 

Now the part where I need your help. Well, the help of those who are familiar with leslies. I'm not one of those, this is my first one, so I'll listen. The treble is going into overdrive at fairly low volume level. I played 008000000 on my XK1 and gradually increased the volume. You can clearly hear that to a certain point the tone is clear and than it starts to add a buzzing sound that sounds like a 1st harmonic to me (an octave). It happens on every tone of the last two octaves, and it clearly adds a harmonic to base tone, so I don't think it's a speaker buzz. The tone remains clear only at very low volume, far too low volume for normal band usage, so I don't think it should be saturating the amp at that low level.

If you neglect the buzzing it can play loud like hell, but that buzzy distorted sound is really annoying. Is that it normal, or the sound should remaing clear all the way throughout the volume range? If it's not normal what could be the cause?

 

Every bit of help is appreciated.

 

p.s. Pictures to come.

Custom handmade clocks: www.etsy.com/shop/ClockLight
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If you don't have it yet then download the service manual from the good Captain's website.

 

4th icon from the bottom on the right hand side. Above it is the owners manual if you want that also.

 

http://www.captain-foldback.com/Leslie_sub/leslie_manuals.htm

 

 

PS

Sevices manuals for the preamp pedals

 

http://www.captain-foldback.com/Leslie_sub/combo_preamps.htm#download

 

 

"It doesn't have to be difficult to be cool" - Mitch Towne

 

"A great musician can bring tears to your eyes!!!

So can a auto Mechanic." - Stokes Hunt

 

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Wow, thanks! I managed to find the schematic and figured a few things out of it, but didn't know there was a service manual available. And it's a good one, everything is in there!
Custom handmade clocks: www.etsy.com/shop/ClockLight
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I promised pictures, here's 2 taken last night with my mobile. (sorry about pic quality).

 

 

http://img5.imageshack.us/img5/2807/imag0372h.th.jpg

 

 

XK1 on the floor, sound comes out of leslie but it still crack and pops. I still have to find the source.

 

http://img812.imageshack.us/img812/7697/imag0376z.th.jpg

 

 

You can see the messy cables that need to be sorted out. Well, maybe you can't see what is out of ordinary, but trust me, the mess is there. It shouldn't be a problem with all the available schematics.

 

More to come....

Custom handmade clocks: www.etsy.com/shop/ClockLight
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If you haven't already done this.....it may help isolate the problem if you can determine if the unwanted sound is coming from the horn, speaker, or both. Run just speaker, then just horn. Signal goes into crossover circuit first, then is split to bass & treble amplifiers. If problem is both speaker & horn then crossover is bad. I wouldn't completely rule out the drivers (horn or speaker) quite yet. I do a lot of speaker reconing & see many speakers (and horn drivers) come in that have ghost notes in certain frequency ranges. Not saying this is the problem with your Leslie, just suggesting not to rule it out quite yet.

 

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Oh, the problem is in the leslie, I just have to locate it! :)

Yes, I did what you mentioned, and I didn't find the distortion appearing in the speaker, only the horn is distorting. Or at least that's what I hear, maybe the speaker doesn't distort so obviously as the horn.

Now, (in case that it's just the horn part distorting) it is either the horn preamp, or the horn itself, right? Could it be that the horn is the problem, even if the distorted "ghost notes" appearing are actually harmonics of the played note?

What I mean is that the harmonics are moving up as I am playing up along the keyboard thus meaning that the generated ghost notes are related to played notes. That sounds like an amp problem (spurious harmonics generated on active element) to me rather than horn itself, altough given my experience I could be wrong. What do you think given your expereience with speakers?

Custom handmade clocks: www.etsy.com/shop/ClockLight
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The horn driver might be bad. Do you have any other high frequency horns you could use for a test? Maybe one in an amp or cab somewhere? Doesn't have to fit in the Leslie, just lay it someplace handy. The horn driver is 16 ohms, don't use a 4 ohm for test (you probably won't find a 4 ohm anyway); 8 ohm would probably be OK for a short diagnostic test...just don't use it to play. 16 ohm is preferred. If you don't have any horns you could try a small speaker (16 ohm preferred). Just temporarily wire it in place of the horn. If you hear the extra harmonics with the temporary replacement then it surely rules out the horn driver. If you don't hear the harmonics then it is not conclusively the horn driver but increases the probability that the driver is bad.

If you have an O-scope then diagnostic testing is much easier.

 

I should mention, disconnect the motors so they don't run during your diagnostic analysis.

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I knew posting here would be a good idea. I do have an oscilloscope at work,it just never crossed my mind to borrow it for leslie testing!

 

I'll see if there are some anomalies on the horn amp output. If the signal is the same regardless of the volume (except the amplitude of course) it probably the horn driver.

 

I also have a Elkatone leslie clone with 16ohm horn driver, so I can use that one for testing too.

 

 

Custom handmade clocks: www.etsy.com/shop/ClockLight
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I would get an Atlas PD-60 or what ever horn driver you want to use and just swap it out. If the horn driver isn't blown ... well it probably will be someday and you will be prepared. LOL

"It doesn't have to be difficult to be cool" - Mitch Towne

 

"A great musician can bring tears to your eyes!!!

So can a auto Mechanic." - Stokes Hunt

 

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Yes, It is probably the horn driver. Personally I don't like to buy parts until I get enough supporting data......that's just me though, I'm kinda cheap.

 

Don't mess with that killer footswitch at all. It is far to dangerous to leave active....for you or any unsuspecting adult, child, domestic animal, farm animal......

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