Leslie 122 with a raspy noise

[King Julien]

Hi all,
Firstly many thanks for all the helpful info in this forum. Its helped me get Hammonds M2, M3 and L111 going over the last year or so.

But now I'm having some persistent trouble with my 122 that I just cant seem to pinpoint. At low volumes there is no problem, but at higher volumes, especially with lower frequency notes, there is a horrible raspy type of noise. I've tried deoxit and cleaning the tubes and the sockets. I tried swapping out the 2 12AU7s for some other ones I had in the Hammond. None of that helped.

The noise seems to come and go a bit. But I'm not really sure what makes that happen. At first it seemed to improve the more I played, but now I think it is becoming more constant.

Could this be one of the other tubes (D3 or 6550s) being on its last legs?

Anything else I could try before buying some new tubes?

My tech (Geoff) did a service on this about 5 years ago and removed the 'death caps', but he lives in another State and has been restricted in travelling due to COVID, so not sure when he will be able to get a look at it.

[tiredoldgeezer]

While "raspy" can mean a lotta stuff to lots of different people... and "raspy" is almost a desirable characteristic among Lord/Emerson players.... my wild guess is that your problem is not in the amp but in the speaker.

Damaged (or just old) speaks can start knocking about inside from long throw excursions causing what could easily be described and "unpleasant and raspy". High volume and low freqs are definitely in this category.

One idea:: Plug in another speaker and test. Remember the Leslie is 16 Ohm. However, if all you have is an 8 Ohm, it will work for a very short test, and won't sound perfect, but it will shed some light on the situation.

[David Anderson]

I had the same idea as TOG. You don't give the age of your 122. Some older woofers have cones that have dried out and cracked around the edge. A careful visual inspection with a flashlight is a place to start.

Edit: I've seen Leslie woofers that had no surround left at all. The cone was just hanging from the spider, and the paper surround was scattered around by the drum.

[Baseman norm]

Lol lol lol

[Jyvoipabo]

Hello,

I don't know if the cross-over are included in the death capacitors replaced.
Anyway, this point needs to be checked.

JP Redeconfined....soon ?

[King Julien]

Not sure what you mean here. Can you explain what needs to be checked in the crossover?

[King Julien]

Thanks guys, good thoughts. The Leslie seems to be from different years, but I think the speaker might be from 1968. I'll look at it a bit closer tonight and get back to you. Can I use a 12 inch from an 860 to test?

[King Julien]

While "raspy" can mean a lotta stuff to lots of different people... and "raspy" is almost a desirable characteristic among Lord/Emerson players.... my wild guess is that your problem is not in the amp but in the speaker.

Damaged (or just old) speaks can start knocking about inside from long throw excursions causing what could easily be described and "unpleasant and raspy". High volume and low freqs are definitely in this category.

One idea:: Plug in another speaker and test. Remember the Leslie is 16 Ohm. However, if all you have is an 8 Ohm, it will work for a very short test, and won't sound perfect, but it will shed some light on the situation.

Definitely not a desirable kind of raspy. I tried unplugging the V21/horns and the speaker one at a time (at the crossover). The noise persisted, and was louder and more clear through the horns. But came through both, so the problem does not appear to be in the speaker.

[King Julien]

I had the same idea as TOG. You don't give the age of your 122. Some older woofers have cones that have dried out and cracked around the edge. A careful visual inspection with a flashlight is a place to start.

Edit: I've seen Leslie woofers that had no surround left at all. The cone was just hanging from the spider, and the paper surround was scattered around by the drum.

Likewise (see above). I also had a good look at the woofer - no signs of cracking. There was a little blob of something on the cone - looked like it could be some melted wax or glue or something, but I am pretty sure its not causing the problem. Couldnt really scrape it off without possibly damaging the cone, so I just left it there.

So next, I pulled out the crossover and dexoited the connectors. Still no improvement. Then more clues arrived. The leslie went into this state that would not switch from fast to stop (I have the slow connectors out as I prefer fast and stop lately). Tried yet more 12AU7s that I sourced from another L100. Then I opened up the Speakeasy pre amp and gave various components a bit of deoxit. Cleaned the tube, replaced the tube etc. Still no good.

Next day I got the Leslie to work properly for a short period. Was switching speeds and noise briefly gone, but low volume. Then just holding a chord and playing a pedal, could hear the volume coming in and out and then the noise returned. Tried tapping on the tubes with a pencil, but I dont think it made any difference.

So, in summary, its an intermittent problem. Its not in the speaker. I've got a feeling its not in the preamp, but I've got no way to really test that theory. Pretty sure I first noticed the problem when I had the Leslie and preamp hooked up to my XK3. So its not the Hammond.

Any next thoughts?

[Jyvoipabo]

Hello.

I summarize.

The organ is not in question.
The speakers are healthy.
The cross over too. But forgive me if I insist. If it is still equipped with the large flat capacitor, it will be necessary to think about replacing it.
On the amp the death capacitors have been replaced. But that was not enough.

At low volume it's okay, but rotten sound appears when power is requested specially on bass. Then he manages to disappear.

A skilled technician would first refer to the diagram and check all the voltages. Beware of high voltage inside.

But first check 25Volts across R12 150 Ohm / 10W. Not dangerous if you connect your voltmeter before mains on.

Also inspect / check that capacitor C11 (200µF / 50V) accross R12 has been changed and not damaged.

Post a photo of the bottom of your amp. We could learn things.

JP

[King Julien]

Hello.

I summarize.

The organ is not in question.
The speakers are healthy.
The cross over too. But forgive me if I insist. If it is still equipped with the large flat capacitor, it will be necessary to think about replacing it.
On the amp the death capacitors have been replaced. But that was not enough.

At low volume it's okay, but rotten sound appears when power is requested specially on bass. Then he manages to disappear.

A skilled technician would first refer to the diagram and check all the voltages. Beware of high voltage inside.

But first check 25Volts across R12 150 Ohm / 10W. Not dangerous if you connect your voltmeter before mains on.

Also inspect / check that capacitor C11 (200µF / 50V) accross R12 has been changed and not damaged.

Post a photo of the bottom of your amp. We could learn things.

JP

Thanks JP

I will post up some photos. I think you might be right about the large flat capacitor in the crossover. I will try and measure those voltages in the amp tonight.
John

[King Julien]

OK, so I started to unplug the connectors from the amp again and noticed that the previously gritty feel of the connector that takes the audio to the crossover was now much smoother. So after a few days its seems the deoxit had been working away at dissolving oxidised material. Then I found I no longer had that raspy noise. I have tried again over the last few days and it really seems to have completely disappeared. So I think that was the cause of the problem.

But on that issue of the flat capacitor in the crossover - does that need replacing at some stage?

[David Anderson]

But on that issue of the flat capacitor in the crossover - does that need replacing at some stage?

Possibly. As far as I know, I'm the first person to have brought up the idea of replacing these capacitors, which was an idea I had back in 2002. The originals are metallized paper, and they can drift in value. The drift, however, is extremely unpredictable and varies greatly from one cabinet to another. It can be severe (>50%) or minor. The effect of the drift is to move the crossover point -- not to cause raspy noises. People tend to make this much more complicated than it is, probably because people tend not to understand crossovers and what they do.

(In Leslie 122A amps, these capacitors are cheaper electrolytic types, and a few have been known to fail, especially in earlier 122A cabinets. But the older paper caps don't fail catastrophically the way electrolytics do.)

I have seen Leslie speaker connectors very oxidized to the point where they no longer make good connections, so that may be what was going on in your case. It's always a good idea to clean electrical connectors every once in a while in anything.

[Jyvoipabo]

Hello,

Deoxit never resuscite a defective electronic component. It is therefore a matter of a contact problem.

To find out if the crossover is healthy, just measure the capacitors. Beyond 10% it is necessary to replace because in filters precision is critical.
I bet they are worst.

You won't find 12.5 and 7.8 µF capacitors.
But you will easily find 1,2, 2,7 and 3,3µ.
So you have to make parallels wirings.
3 x (3.3µ) + 2.7 = 12.6µ
2 x (3.3µ) + 1.2 = 7.8µ
That is 7 capacitors Axial polypropylene 250V with long leads to buy because they are easy to wire.

JP ReDeconfined or not ?

[David Anderson]

Or just buy a single 7.5uF capacitor and a single 12uF capacitor, both readily available values. No one will ever notice the difference. Both those are within 4% of the original targets. There's no need to wire up a bunch of capacitors in parallel, unless you won't be able to sleep at night if you don't.

[Jyvoipabo]

Or simply buy this:

JP

[David Anderson]

I know the owner of TWG, and we discussed which capacitors he would offer prior to adding these to his site. From a customer satisfaction standpoint, he thought it was best to offer parallel combinations that add up to the exact original values, and from that perspective, it makes sense.