Noisy Transformer

[deadlydave]

Hi all

The Gorgar had a very loud hum when turned on which I assumed to be coming from the tranny. Ive put up with it for a while but had a look at it tonight, I checked the bolts that hold the laminations together and they were all tight, mounted the tranny back on some rubber grommits thinking that would do the trick, put cage back on and when I turned on still very noisy. I then took the cage off and tried again this time as quiet as a mouse. So coming from the cage, I tried putting some foam under the cage were it mounts but still no good. I assume this is caused by the ferrous cage surrounding the magnetic field of the tranny? Had a google but cant find much info, have any of you had similar problem? Got a fix? I've left cage off for now, but would like to put a cover back on, have similar perforated metal at work in stainless, might try to make one up out of this and see if the hum then stays away?

Cheers
Dave

[Marty Machine]

Would it be easier to replace with a plastic cage/project enclosure?

I imagine the cage is copping a fair magnetic field and being energised at 50hz, or acting as an additional secondary winding.

Can you try mounting the cage with nylon/plastic/rubber fasteners instead of metal bolts?
This may isolate the cage from acting as a patially-shorted secondary.

Magnetic flux is always black magic 
MM.

[dj10555]

I came across a noisy transformer in a WPC game and it turned out the game was wired for 210V. Changing it to the correct jumpering fixed the problem.

[deadlydave]

Hi Marty
I could fold up some plastic, but not sure if it would get too hot?
I think it best to have the cage earthed, but perhaps at only one point may help?
Not 100% sure about tranny wiring, have not got schematic yet, but tranny itself is dead quiet and
hum is from cage.
Cheers
Dave

[FirePower]

http://www.firepowerpinball.com/downloads/PowerWiring.pdf

will get you the wiring diagram, this is for Firepower, but it will be the same for Gorgar.

If it were me I think I'd just try and stiffen up the cage mountings.

[deadlydave]

Thanks Firepower, I forgot about those drawings 

will have a look.

I really dont think its the mounting, I put beer seal foam between all points in contact with headbox,
and fixed down well but the cage hums like crazy 

[deadlydave]

Well DJ10555 was on the money, tranny was wired for 210VAC, have changed to the 240VAC tap and all good now, very quite with cage mounted over the tranny. Thanks for all the replies.

Cheers
Dave

[Marty Machine]

Nice fix!

That'll be one we won't forget anytime soon 

MM.

[Pinprick]

The actual reason transformers hum is . . . . . .





They never wash. 

[dj10555]

Glad you found the problem. The transformer would have been running hot on the incorrect setting and also would have put stress on regulators, etc in the long term.

regards Derek

[deadlydave]

Looking at the tranny tabs, I think it was wired to the low line from day one, have not noticed much diff in gameplay, its all good.

Cheers
Dave