Fault-finding hum(s) on a Liverpool - Distress call

[plook]

can you move it or the OT? Are they interacting with each other to cause the hum?

Unfortunately not. I have tried all of that. I have taken the MT off the chassis now and connected it up and it hums the same on it's own. i should have tested this before i did anything else. I have a tendency to buy parts and build much later.

[zambo]

I also read somewhere if the laminations are loose they will hum. I had one do this and after tightening the bolts to hold it together it stopped. fwiw. sorry i couldnt be of more help.

[M Fowler]

Remove that PT call Heyboer and say you want it inspected for flaw. They will stand by their work.

I have had some bad PT's myself in addition to a dirty AC line on my work bench that took almost a year to track down.

Mark

[v846]

is the copper band loose?

[M Fowler]

Well there has been issues with PTs from various manufactures not just Heyboer.

The flux band is loose, bent mounting tabs, dented end bells, and improper lamination causing vibration. Not to mention terrible looking hunk of iron.

All the Edcors have looked good but have thin mounting flanges. I have had no problems with Edcor myself.

Pacific have worked well and looked good.

Heyboer loose flux band and physical vibration. Two units only. Appearance average.

MC all have worked well, about average in appearance. Mine don't get hot like others have problem with?

I don't use MM iron.

Mark

[plook]

I took the transformer clean out the amp and it had the same problems, so i contacted Heyboer and they have been great. Given me some tips on how i might be able to stop the hum by tightening the copper foil strip and putting silicon sealant under it. I'm just waiting for it to cure before trying it again.

I did wonder if the 240v 60 cycles UK AC might be an issue but i have many other Heyboer and MM transformers in other amps and they are as quiet as a church mouse. I made an Overtone Special amp a couple of years ago with a Heyboer PT and when you turned on the power it was silent, so i think it's just down to this transformer really. Problem is, i'm in Sheffield UK and i bought it in the states, shipping costs these days are just sky high, so it's going to hurt someone a lot, just hope it's not me.

It's weird, for so long i thought my TW Liverpool was at fault and i put it to one side for a year because it drove me absolutely nuts. i should have pulled the transformer sooner, but newbie builders have a tendency to think the gear is good and the build is at fault.

[kwijabo]

so just to clarify for myself - the actual transformer itself is what is humming? It's completely out of the amp and yet there is an audible hum from it?

If that's the case, was the hum louder when it was attached to the amp? Just curious if it's hum got coupled into the amp then amplified. I've never experienced this so i'm curious about it. thanks...

[John_P_WI]

I know this is subjective, but how loud is the hum? Virtually all of the "50" watt and above transformers that I have used have made some type of hum. Yes, mechanical hum. It is especially apparent when the chassis is out of the cab and is more pronounced if the chassis is "upside down" resting the transformer laminates on the bench top.

I suppose the mechanical hum may be exacerbated with the 50 hz mains that you have there as well.