Carverfest Tube Amp Transformer Hum

OK, a couple of questions:

Some of us are experiencing some transformer hum in reference to the large transformer from my understanding. I am referring to the transformer only and not through the speakers.

1. How hot do these transformers get?
2. Don't know if there is room or not, but would a non-flammable dampening material on the inside of the transformer cover, providing there is room be a no-no? I haven't researched a product like dynamat or a similar product regarding flammability yet. Just kicking around an idea that may or may not be worth exploring.

Will turn my amp on tomorrow for several hours under a load to check heat output. Initial thoughts, anybody?

Don't do it! It will more than likely end up as a pile of goo....

Man, that bites . Short of replacing the transformer(s) or having them dipped, you might could try to adjust the windings by removing the cover and gingerly pushing them back or forth, possibly to the right or left while powered up and while using rubber gloves [that are rated for 120/240v protection] with preferably a good leather glove over that as further protection from electrocution. Another thing that is ghetto as hell but sometimes effective is to wedge a small ball or folded piece of vinyl electrical tape between the housing and the windings to try to hamper the windings that are creating the hum. Once again, you have to work it while powered up and you have to use the proper protection. Those are about the only options I can think of and at the end of the day, may or may not even work. If you are not comfortable working with live electronics, do not even consider this an option.

Personally, I would replace the transformer if at all possible.

Does anyone who has a Carverfest amp NOT have a noticeable hum? Don... Don't fool with the transformer with the amp on unless the 75 is left to me in your will....

Does anyone who has a Carverfest amp NOT have a noticeable hum? Don... Don't fool with the transformer with the amp on unless th 75 is left to me in your will....

Now that is what this forum is all about,,kindness and caring.

hmm. mine is dead silent. we shall see with the other 6 one day soon.

Out of the 4 I bought I have 2 assembled one has a hum and one does not. 50/50 aint bad odds .right?

OK guys,

Thanks for the response and thoughts. Tom, do not feel comfortable working with live A/C. You saw my soldering skills. But thanks for your thoughts.

Kingman, feel the love! Dan, good point on the stuff turning to goo. Didn't realize how hot these puppies get.

OK-next crazy thought-muffler/exhaust/header tape lined on inside of transformer cover? Notice is good between 800 to 1200 degrees F. Of course, need to make sure it is non-conductive and have adequate clearance between transformer cover and transformer.

Will probably catch up with Bob at Axpona and get his thoughts on replacement/options before doing anything. Currently have 3 and waiting on 4th. 1 out of 3 has significant transformer hum which can be heard from listening position.

no hum on my 1 amp don!! think I would replace transformer myself!! trying to muffle the sound dont sound like a good idea!! just my .02

Ok...where do we get replacement transformers and is there a guarantee that THEY will not hum??? Alex???

there has got to be a name & some sort of # on them? try seaching the web is what I would do first!!

The company that made them is Edcor. They're really nice folks. Called them for the weights of the transformers back when I was getting mine shipped.

http://www.edcorusa.com/default.aspx

Transformers make physical noise for a few reasons.

The cover screws being loose is the first and easiest to deal with. I'd suggest first trying to tighten them up. Be gentle yet firm with those screws through the four corners.

Pulling current in sharp little spikes is another and I'd suggest this is likely to be involved in this case. The sharp turn on and off of the current pull is what sets up the vibrating conditions that makes noise you can hear. Whether this reaches audible or not depends on the mass, the current pull versus that, and the tension on the windings. The size of the capactors and the overall PS design plays in to this. Buying and installing better diodes is very inexpensive and a really good idea for sonic reasons anyway!

Another is being too much current for the design. Poorly made with not enough steel or loose windings can make a situation and physical noise. You might want to check the bias voltages and make sure you aren't contributing to a problem by pulling too much...which would eventually lead to tube failures if you are.

Potted transformers helps hold the windings physically. More expensive iron is often potted and physically bigger to help keep this noise from happening. If the power line has a lot of noise for some reason, this can make this problem worse too as the higher noise hits the magnetic field.

You can google and get more comments on all of these situations.

Mark

Mark,

Thanks for the comments. Since this is a Bob C. design, will have to believe design parameters were met as far as diodes, transformers, etc.

I guess the only thing I am really capable of checking are the screws you mentioned. If that doesn't quiet the puppy down, I will talk with Bob at Axpona, if he has the time after show hours, about a replacement transformer. Mike, also thanks for the link.

yeah, theres no doubt in my mind that edcor has some kind of warranty. question really is if they have any available as these were made to bob's specs. remember that the output transformers were done twice as the first batch was not up to bob's liking. worst case senario would be on the output transformers and not the power ones.