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How deadly is transformer hummm...

Hello Folks,

I recently collected a lightly used (less than 50 hours) Dennis Had - Inspire - "Fire-Bottle." Within some few days, I noticed a humm emerging from somewhere within the chassis of the unit. As the unit was sold in "perfect" condition, I found the humm startling. Mind you, I've discovered absolutely no evidence confirming the sound is compromised; I mostly hear the sound within a couple feet of the amp, when the surrounding environment is silent.

This amp truly is a work of art. Nevertheless, I am now dealing with this 'humm' sound. I bought an Emotiva CMX-2 as a way to deal with DC offset, and this has not impacted the situation to any detectable improvement. Perhaps there is a slight improvement, but negligible. What to do?? Should I just relax, shake it off, and assume the amp will live well, or a down-the-road transformer replacement will simply become part of my experience with this amp? Should I put pressure on the seller to "right" the situation? He claimed, as I asked him, that it was the quietest amp he's ever owned. His add boasted that the fire-bottle exceeded amps from Pass Labs, a Cherry Amp, and one other that escapes memory. The seller has presented all of his communication in the manner of friendly professional etiquette. 

Your thoughts are appreciated. 
listening99
Post removed 
wolf_garcia
6,610 posts
 
If you place your ear near the transformer of a Firebottle you could burn yer face off. 
listening99 OP
172 posts
 
I've got an email out to the seller of the amp, to see if he can reach out to Mr. Had, for some advice. The amp was made in April and there shouldn't be any transformer degradation of significance by this time. I would open it up with a little clear-firm guidance, but I am recollecting that my last rash of flirtation, soldering gun in hand, was over thirty years ago in a high school classroom. 

Thanks for the new vocabulary word: isomerics

@wolf_garcia has me interested in the heat resilience of the purchased washers and I've discovered that they are more durable than the skin on my face. According to the Home Depot account for DANCO 1/2 flat washer 3/4" O.D.:
  • Can withstand heat between a temperature range of 86°F-248°F (-30°C-120°C)
Would 248F handle the temperatures within the amp @atmasphere ? I'm not convinced, because it's quite hot to the touch, once it been in operation for an hour or more.

Can anyone speak to the expected problems with this kind of symptom? One person claimed it could clear up... I imagine the amp has around 100 hours on it by this time... 
oldhvymec
5,101 posts
 
No rubber or BRubber or anything  other than silicone.  I have a few noisy transformers that had mechanical hums. Mounting issues. 

Not all silicones are the same. The super HIGH temp. silicone can be conductive. Silicone washers are OK BUT, read below..

Put your hand on top if it FEELS, mechanical, press down, can you dampen the noise? Turn off, UNPLUG, remove the valves, flip it get a 40 watt bulb with pig tails, discharge the caps. Work.

A little dab will do ya!  LOOSEN the securements. don't remove them.
Get a pin applicator (smaller high pressure needle gun) A small grease gun will work. give it a little shot, not more than a BB amount.  .177-.180
at each securement between the two surfaces. Tighten. Let it dry, and try it.

Still hums

Check the valves, PULL and reseat move them (pencil tap test) around see if the noise changes. BAD VALVE.. Have to check them
Valves are good.

Still hums

Make sure the voltage is 120. I have a few Cary designs, they like 120VAC, not LOW. They will hum. Easy to check and or fix. Voltage maintainer or Variac, will really tell the story. Start at 110v slowly go up, the hum will go away at 118-122VAC

Still hums

????? I'm out of low cost easy fixes, go find a repairman. Everything I offered is under 10.00 silicone an High pressure needle gun.

Happy hunting

Regards
listening99 OP
172 posts
 
...and now I have email out to Dennis Had...
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