Power Transformer vibrating and humming. Ideas appreciated.

[Rockeraaj]

This is my first post on this great forum. I completed my TWreck Express clone today. This is only the second amp I've built (I also did a JTM45). I feel more like a modeler than a knowledgeable amp maker. I used a Ceriatone chassis and Toneslut Transformers, including the Vintage output transformer. I played it today, and it gave me shivers how great it sounded (Ken Fischer is a god). I'm guessing some break-in will improve it more. I noticed one issue that has me worried, the Power Transformer vibrates and hums and there is humming coming from the speakers. This will happen even with no tubes in the amp. Like I said, it sounds and works great otherwise. I read another post about the vibrating transformer being normal, but I'm worried about the hum out of the speakers that happens even without tubes. I think it should be quiet without tubes. Any ideas anyone?
Thanks, Aaron

[jjman]

Possible hum induction thru the air from the power tranny. Are they mounted parallel or 90 degrees off each other's axis?

Could also be some wires lined up on top of each other that shouldn’t be.

[Rockeraaj]

The transformers are set at 90 degrees to each other, give or take a degree. I'm thinking it could be hum induction through the air because the tone is the same at the transformer as the speaker. Is there something wrong with the transformer? Or is there something wrong with my circuit? Although I was very thorough with the build, and it sounds perfect otherwise. Could it be the unneeded transformer wires laying under the power supply board? Thanks for the help!
Aaron

[jjman]

............ Could it be the unneeded transformer wires laying under the power supply board? Thanks for the help!
Aaron

I'm thinking unused OPT wires laying parallel to 60hz wires could be the problem.

[rawnster]

Hey Rockeraaj, I'm interested in this topic, for I get the same vibration and hum you mentioned. Yet, all of the unused OPT wires are clipped way back and shrink wrapped.

[Rockeraaj]

I am using the Toneslut Vintage spec output transformer and all of the wires are being used. The only wires I have shrinkwrapped are coiled up under the power supply board and are the unused rectifier lines and unused 260v lines of the power transformer. I wasn't very clear about that. Is OPT short for output transformer? If so, there are no unused wires. This hum happens with absolutely no tubes present in the amp, which leads me to believe it is likely some kind of induction hum from the PT to the OT. Is my logic correct?
Aaron

[Structo]

Well of course it could be heater hum.

Are any of the grid wires too close to heater wires?

Also make sure your B+ wire to the standby switch is away from the ac wires.

I had that happen on my D'Lite and once I moved that wire away from others the hum went away.

I'm thinking it is a 60 Hz problem rather than a transformer problem.

[Darkbluemurder]

Does the amp also hum when it is in standby mode? If so the power transformer could induce hum into the circuitry. Check its orientation. If it turns out to be wrong you could either try to rotate both the power transformer and the output transformer by 90 degrees or put a shield between the power transformer and the rest of the circuitry.

I had this problem in my early 90s JTM 45 RI. When I replaced the power transformer with a stand-up mount unit orientated correctly the hum was gone.

Good luck
Stephan

[Rockeraaj]

I've emailed Chris at Toneslut, and we've decided to replace the humming and vibrating PT. You can hear the transformer hum from across the room with no tubes or input while on standby with the speaker unplugged and the chassis in the cab. When the new one comes in, I'll do the swap and go from there. In the meantime, it does appear that there is indeed induction between the PT and the OT. Chris/Toneslut is wonderful, by the way. I wasn't all gung ho to replace the transformer, but Chris thought it was the way to go. That's integrity and customer service right there.

I'll update here as things progress. Thanks, to everyone.
Aaron

[jjman]

I hate vibrating trannies. They scare me. I changed one in my HVAC system once for that reason. Got the replacement from the DJ equipment company I worked for at the time. Probably 117v<>24v or so.