145 Treble Distortion and Buzzing

[theseacowexists]

I've noticed some distortion/buzzing in the treble driver of my 145 pretty much since I got it a few months ago. Somedays it's worse than others. Definitely more noticeable on the lower frequencies that are going through the driver. Bass speaker doesn't have any of the distortion, just the expected overdrive you'd get when cranking the volume.

I finally figured I should clean out the horn, since the entire cabinet was filled with dust and crud when I got it, but I never got around to getting the horn assembly apart to clean that. So I'm figuring that maybe there's some junk in there that could be causing that buzz. Sure enough there was plenty of dust in the throat of the horn and even in the driver, which I carefully removed. A rubber band was also hanging around inside there, not attached to anything, but I removed that as well.

Now it sounds like this (Leslie volume on 2, bass speaker unplugged):

https://youtu.be/nqTAh-Gnpbk

Maybe all that dust was covering up that distortion!

So my question is, which of the following should I do first to troubleshoot this?

-recap the amp (I have all the parts already, just haven't done it)
-recap the crossover (I've read that if the caps drift then frequencies which shouldn't go to the driver, do)
-replace the driver (hopefully not!)

[muckelroy]

Recap your amp. Doesn't matter if it's the root cause or not. You're playing with a time bomb if the coupling caps are original.

You shouldn't be getting “bass frequencies” in your treble driver. The crossover point should be somewhere around 800Hz. Recap it.

If all of this is done properly, it should not make the problem any worse. Then you at least rule them out.

[Goff]

All of the above.

Check your tubes against fresh or spares.

Some hang onto the V21 sound, but an Atlas replacement will work, just need to reorient your bar pulling habits.

There are many V21's out there for sale. So all is not lost.

[Jyvoipabo]

Hello,

I am confused.
If it was a capacitor problem, we could expect 60Hz or 120Hz noise.
But this 800Hz looks like a very regular motor sound.
If it sounds like a motor, there's a motor somewhere.
May be a particularly noisy environment or a noisy power line.
Check the isolation of the mains from ground and of each electrical contact.
Move the power of the cabinet to another plug.

JP

Before recording, did you unplug all the motors of the Leslie ?

[David Anderson]

To be honest, I'm not entirely sure what I'm listening to in that video.

V21 horn drivers sometimes need realignment of the diaphragm. It is a very common job for Leslie techs. Unlike more modern horn drivers where there are locating pins that fix the diaphragm in the right place, Jensen V21 diaphragms are simply sandwiched between the faceplate and the magnet structure. If the diaphragm is not centered in the magnet gap, it can buzz.

[theseacowexists]

David, I had a hunch that it was the diaphragm that needed alignment. Sure enough, opening the driver, loosening the screws and then wiggling it just a little bit must have knocked the diaphragm back into place. No more buzzing! There was some crud in the driver assembly too that I cleaned out while I was in there.

This video helped: https://www.youtube.com/watch?v=O6XfMVj1yng&t=521s

I'm still going to recap the amp, I just needed to get rid of that noise before a session this week. Thanks y'all!

[theseacowexists]

Update/bump...

Amp and crossover were both rebuilt not long after the previous post, and the Leslie sounded better than ever. However, the buzzing has returned on a couple occasions. It's remedied the same way each time - just slightly loosening and then tightening of one or two of the screws that hold the diaphragm. The fact that I need to keep doing this bugs me though, is it a sign that the driver might be on the way out? The Leslie lives on a furniture dolly and does get bounced between a couple rooms for recording purposes, but it never leaves the house. But maybe that's just enough vibration to knock the diaphragm out of alignment occasionally?

[Jyvoipabo]

Well done ! If after changing all the capacitors, the noise has not disappeared, the conclusion is : The noise was not related with a capacitor problem. And, I don't think it's a problem of horn. If it were decentered it would be scratchy, but this is not the case. By tightening the screws you have to move something that makes the problem go away. I think of a bad contact that the vibrations of the motor amplifies. Unplug all the motors of the Leslie, with no sound, move all the wires and connectors starting from the power plug passing by amplifier till horn. It can't be bad to inspect and well clean its screwed connections. Then, tap gently all the parts with the handle of a screwdirver. Looking for a sensitive area. JP

[NittyRanks]

It amazes me how many Leslies are let go and in piss poor shape.

[David Anderson]

If you're not experienced in doing it, realigning a V21 driver diaphragm can be tricky. Sometimes a little piece of trash has gotten into the voice coil gap, and the gap needs to be cleaned out with sticky tape. Alignment can change when you tighten the faceplate screws. Over time, you get a feel for how to do it. Occasionally, you get one that can't be realigned, and that's usually because the diaphragm has warped such that the coil former is at an angle inside the gap. It's not always easy even for experienced techs.

[NittyRanks]

How did you make out? Good to see you last week man.

[muckelroy]

If you're not experienced in doing it, realigning a V21 driver diaphragm can be tricky. Sometimes a little piece of trash has gotten into the voice coil gap, and the gap needs to be cleaned out with sticky tape. Alignment can change when you tighten the faceplate screws. Over time, you get a feel for how to do it. Occasionally, you get one that can't be realigned, and that's usually because the diaphragm has warped such that the coil former is at an angle inside the gap. It's not always easy even for experienced techs.

If you're not careful, it is easy to ruin the voice coil. Sadly, I speak from experience. I have a couple in my parts bin which I need to replace the coil on due to my past brutality.

[theseacowexists]

Another bump/update...

That dang buzzing came back two or three times in the past year. I finally said enough is enough and ordered a new diaphragm from TWGH. The difference is night and day. Lack of any buzzing aside, the V21 now seems just clearer and more powerful than before. The old voice coil had a small crease around the edge, I'm sure that could have been a major cause of it.