Issues with Hammond CV and Leslie 122 -- scratchy noise and high speed flutter.

[glensound]

Issues with Hammond CV and Leslie 122 --intermittent scratchy noise and high speed flutter from the horn. I have recently removed, oiled, and reassembled the horn.

I am trying to attach video, but not sure what format the video file needs to be to be uploaded?

[glensound]

Here is the video: https://youtu.be/VjGvTKcIUpM

[enor]

The scratchy noise is likely the preamp in your Hammond needing an overhaul. The "flutter", as you call it, sounds like a bad idler bearing in the belt tensioner for the horn.

[Hamman]

I'd definitely change out all the motor mounting rubber grommets. That and or check for a ground loop issue with the amp for that hum noise. Did you try putting a drop or two of oil on the idler bearing? Motor(s)? Horns on high speed do make some whirling noise....

[glensound]

Idler spring and bearing are quite new and hasn't seen much use. I have oiled the bearing and the horn, but will look at that again. Any particular oil, as I used the hammond organ oil? It does seem like maybe I need a new tube set for the preamp. I have pulled and reseated the tubes, but they have never been replaced since I have owned this organ, back in 2005. As for the ground loop, I am not sure where to start looking into that.

[enor]

In my experience, oiling that bearing never makes much lasting difference. Much better to simply replace the idler bearing. It's an encapsulated type 635 bearing.

[glensound]

In my experience, oiling that bearing never makes much lasting difference. Much better to simply replace the idler bearing. It's an encapsulated type 635 bearing.

I noticed that the wing nut on the idler was not tightened at all... It seems OK. As I said quite new. It may have caused a rattle. New rubber motor mounts a few weeks ago.

I am wondering about the preamp - is it best to replace all tubes? Where is the best place to get these? Also, are there capacitors to replace? I am not sure what model number this is. It has the metal dome in the middle. 2-6SN7 2-6SJ7 1-6J7 I think.

[enor]

I noticed that the wing nut on the idler was not tightened at all... It seems OK. As I said quite new. It may have caused a rattle. New rubber motor mounts a few weeks ago.

I am wondering about the preamp - is it best to replace all tubes? Where is the best place to get these? Also, are there capacitors to replace? I am not sure what model number this is. It has the metal dome in the middle. 2-6SN7 2-6SJ7 1-6J7 I think.

Scratchy noise is probably not a tube problem, more likely a bad resistor. I'd just have the preamplifier rebuilt; but I have noticed many techs in the US advising against that, suggesting a TREK2 preamp instead because in their words rebuilding a CV amp isnt "cost effective". I've never quite understood why. Sure, space is tight in the CV preamp so it's a bit fiddly, but all in all it's a very uncomplicated amplifier.

There are capacitors in the preamp, but the most urgent ones to replace will be those in the power supply - which is separate from the preamp in a CV. And, those will typically cause a much lower frequency "mains hum", not the scratchy treble noise ("popcorn machine") that we hear in this case.

[glensound]

That's a lot of great information! I have pulled the preamp. Where is the power supply located in the CV? I'd be interested since I am having the preamp looked at by a service tech. He's rebuilt my 122 amp and is very thorough and he will only replace what is needed.

[enor]

That's a lot of great information! I have pulled the preamp. Where is the power supply located in the CV? I'd be interested since I am having the preamp looked at by a service tech. He's rebuilt my 122 amp and is very thorough and he will only replace what is needed.

A stock CV doesn't have a power supply, the high voltage for the amp is provided by the tone cabinet (or Leslie, if it's a "Hammond type" such as the 122 for instance). Many CVs have had a power supply added on afterwards though, for "standalone operation" and easy connectivity to other types of cabinets.

[David Anderson]

That's a lot of great information! I have pulled the preamp. Where is the power supply located in the CV? I'd be interested since I am having the preamp looked at by a service tech. He's rebuilt my 122 amp and is very thorough and he will only replace what is needed.

I've rebuilt a number of CV preamps. These things are from the 1940s, and you should replace a large proportion of the components in a rebuild, including all the 0.02uF paper capacitors and resistors that are out of tolerance or which could become noise sources. It makes no sense to leave an >70 year-old paper capacitor in place because it hasn't failed yet. They are not fun to rebuild due to the cramped nature of the box. The oil block capacitor on the side is likely still good.

It's not a good idea to apply the same parts replacement protocols to 1940s electronics that you might to something made in the late 60s or 70s. There are no parts in a CV preamp that create "magic tone."

Here in the U.S., most CVs have not had independent power supplies installed, at least where I live.

[glensound]

I had my CV preamp rebuilt about 6 month ago and the organ was fine, but now the scratchy noise has returned. It doesn't seem to affect the power or volume of the Hammond organ notes at all, so when playing loud it isn't that noticable.

(I should also say that this whole problem had caused me to take the horn assembly apart and I found worn rubber bushings which were responsible for the horn wobble. Once replaced with new rubber, the horn was much quieter.)

The scratchy noise seems to take about 15 -30 seconds after initial power on to start. The longer the organ is powered up the more profound the noise seems.

I guess I need to start looking into a possible problem inside the 122 amp.

Any insight into this recurring noise issue would be greatly appreciated.

Hammond CV 1945
Leslie 122 in 145 cabinet w/ solid state relay
Trek II percussion and speed switch

[David Anderson]

Scratchy noises are typically a bad connection; the noise is the connection opening and closing. The thing is, it can occur anywhere there's an electrical connection of which there are MANY in an organ/tone cabinet system. Tube pins can be an issue. Leslie cable connectors can cause this. It can be a bad solder joint. It can be a bad weld inside a tube itself. I've seen them all.

I'll often wiggle things with the organ running to see if I can find the source. If I can't, I just have to start analyzing the signal chain and breaking down where the noise seems to be coming from. For example, if I turn the volume down on the Leslie, does the noise decrease or stay the same?

[glensound]

The organ has lots of volume and will override this noise. I will test the Leslie volume.

With this problem, it is immediately apparent at power on, or it won't happen at all until the system is powered off then on again.

I have a suspicion that the vibrato control seems to be in play here since turning the knob to the off then back to the on position(s) will increase the scratchy noise. Just a guess.

Is there a way for me to disconnect the vibrato altogether as a test to see if this function is the cause?

[Drawbar Dave]

Fixing it might be something as simple as dirty tube pins or sockets. My friend's A100 had this problem in the reverb channel and a simple clean up when I was visiting him solved it. I usually work through the simple stuff like tube sockets and then move on to cable connections etc before taking the organ apart.

Try wiggling the vibrato tube to see if that increases the noise or pull the vibrato tube failing that.