Neoprene

ken99

I want to put this stuff under 2 output transformers on a tube amp. Small mechanical hum from them (does not go thru speakers). Not sure what kind to get - seems to be different types available.

Also, will I have to ground the transformers to the chassis with some wire?

I read in a tube amp builders book that Neoprene should be used as a gasket between the amp and the output transformers. Morgan somebody wrote it.

Thanks
ken99

ken99

OK, I pulled it apart to tighten the chasis bolts because I could move 3 out of 4 of them on one transformer with my fingers! It is not much wonder since this is one of the most traveled amps in the history of Canada. It went through about 6 owners in the US and left Illinois for California, then to me in Eastern Canada, then 4 trips to Ontario for repair.

I decided to pull off both output transformers while I was at it. I put the Silicone Baking Mats gaskets that I had made under each one. I then put lock washers on the new bolts I installed. I did not touch the bolts on the windings because they were painted on there and didn't move a bit since they were installed.

It now sounds wonderful. Reduced the mechanical hum to nothing on the amplifier. Now I just have to get into that power supply and do the same thing to those transformers!

It is a McAlister PP-150 amplifier. Separate power supply with about 6 transformers in there.

I got the suggestions from a complete stranger called Nate at another Internet site.

I hope these solutions help someone else out there.

later,
ken99

hewlew1

Good to know . I have a tube amp that has this issue,since the transformer is mechanically fastened to the chassis I guess it would have an amplifying effect on the hum.

ken99

Hey hewlew1

Something else that I did in addition to the silicone gasket was this:

I went to the local hardware store and got some red/orange rubber gasket maker in the plumbing section. It comes in large rolls 1/8 inch thick and they cut it off for you. You can also buy it in smaller blocks, or packages. Do not use the cork one. I then cut it into small squares about 1" to 1.5 inches square (several laminations). I removed the outer sides (shells) and put the rubber gasket laminations (which I taped together with electrical tape around them all) between the windings and the shells. I used electrical tape to stick them to the windings. They were just slightly snug. This prevented the shells from singing or humming due to the wire moving because of the magnetic field and the current flowing through the conductors. You just have to make them snug. Don't try to put in too much. Too little is just as bad. This made them so quiet it was amazing!

I got this tip from Roger Hug, who is a tube specialist and tube repair specialist in Washington State.

Thanks Roger!

later,
ken99