Noisy Power Transformer 120hz buzz

[bal704]

I'm in the middle of a build, and I've got a buzz I'm trying to get rid of. When I kick on the amp, in standby, the power transformer has a hum to it as soon as power is applied. From this site here:

http://plasticity.szynalski.com/tone-generator.htm

It sounds like a 120hz buzz, and can be heard if I put my ear a few feet from the transformer. This buzz is also audible once I kick the amp out of standby, as it can be heard coming out of the speakers as well. The amp also has a vibration you can feel once the power is kicked on.

I've tried increasing my power supply filters, but it doesn't seem to have any affect on the buzz coming out of my speakers.

Any tips or suggestions on how to get rid of this buzz?

[pdf64]

Maybe there's excessive coupling between the PT and OT?
Consider re-orienting them http://ampgarage.com/forum/viewtopic.php?t=27502

[xtian]

Some PTs are born unbalanced, and the alternating magnetic field just causes the damn things to hum all on their own when energized, especially when bolted to a chassis that acts as a sounding board. These are best identified early and sent back for replacement.

[bal704]

I usually do the headphone test, but I'm using a chassis that was pre-punched for this set of Xfrmrs, so I didn't do that test this time.

However, I loosened the OT and was able to rotate it a fair amount while playing. That didn't change the hum at all.

Maybe there's excessive coupling between the PT and OT?
Consider re-orienting them http://ampgarage.com/forum/viewtopic.php?t=27502

[rp]

Some PTs are born unbalanced

I've had expensive hifi do this both the toroids in ss or the e-cores in tube and was always freaked as it was big money (for me anyway) - but it always came and went , and I can't imaging that all these very different amps had bad PTs, so I figured it must have been the supply in my shitty old Manhattan walkup, or something industrial nearby dirtying up the power. It would happen for 3 days or three months and there was nothing I could do about it, tightening nuts, cheater plugs w/ lifted grounds, line conditioner, ferrite chokes, VPI Magic Brick, 50ft extension cord to an other outlet across the apt, just had to wait it out. Not saying you don't have a wanky PT but you might want to try different venues, time of day - time of year

[VacuumVoodoo]

Have tried to tighten the bolts holding the core together?

[roberto]

^ this

[bal704]

I'll try it. Educate me on how to do it. Here's pics of the PT..

[IMG768]http://i755.photobucket.com/albums/xx198/bal704/DSCN1141.jpg[/img]

[IMG768]http://i755.photobucket.com/albums/xx198/bal704/DSCN1140.jpg[/img]

[IMG768]http://i755.photobucket.com/albums/xx198/bal704/DSCN1139.jpg[/img]

Have tried to tighten the bolts holding the core together?

[Structo]

Some are just noisier than others.

My 100w buzzes a bit.

[Phil_S]

Have tried to tighten the bolts holding the core together?

I'll try it. Educate me on how to do it. Here's pics of the PT..

With a screw driver and a wrench. If you are tempted to use a pliers, don't.

[bal704]

I've already tightened the screws as tight as I can without stripping out the slot head.

Do I need to take this apart to do something?

Have tried to tighten the bolts holding the core together?

I'll try it. Educate me on how to do it. Here's pics of the PT..

With a screw driver and a wrench. If you are tempted to use a pliers, don't.

[Gaz]

No, you did what you were supposed to. You're lucky you did not snap those long thin bolts which do not take kindly to a lot of torque (learned the hard way of course). Honestly everyone recommends that and it works 1% of the time. 99% of the time the transformer is a just a lemon.

I've already tightened the screws as tight as I can without stripping out the slot head.

Do I need to take this apart to do something?

Have tried to tighten the bolts holding the core together?

I'll try it. Educate me on how to do it. Here's pics of the PT..

With a screw driver and a wrench. If you are tempted to use a pliers, don't.

[Leo_Gnardo]

Does the buzz noise reduce when you unbolt the transformer from the chassis - leaving the wiring in place?

Just had a similar problem with an 75-ish MusicMan HD 130. The racket stopped when the transformer was loosened from the chassis.

I widened the mounting holes a bit and re mounted the transformer with silastic washer/grommets. Noise reduced to the point I have to put my ear on the amp's box to hear any buzz.

If your transformer still makes noise when unbolted this solution won't work.

[Stevem]

If it's coming from the winding pack being loose on the core the only way I have ever been able to tone it down is by getting some black automotive silicone sealer and packing a good bit of it in the gap and giving it 8 hours to set up.

[rp]

If it's coming from the winding pack being loose on the core the only way I have ever been able to tone it down is by getting some black automotive silicone sealer and packing a good bit of it in the gap and giving it 8 hours to set up.

Got me thinking, at least before chucking if it's that annoying, put it in a slow oven for a few hours to loosen it up and maybe it'll resettle a bit tighter when it cools?