HELP! Melting transformer

paulb

Member
2001-06-01 4:53 pm
Calgary
More information?

We'll need more information to help you out. What amp circuit? What is the power supply circuit?
In general:
Use an ohmmeter to check for short circuits. You've probably got one. Note the transformer secondary will be very close to 0 ohms.
Use a variac to power up for the first time, or temporary power resistors to check current levels. Even a light bulb in the AC side can be used.
Run up the power supply separately. WIth no amp connected, you can use smaller fuses - if they blow, you've isolated the problem.
Got any pictures? Oops, I guess that's like Morbid Curiosity...
 
it is a power follower. the power supply is made up of just two bridge rectifiers - one for each secondairy, capacitors and a transformer

what should i connect the ohm meter between?

should the light bulb go before or after the transformer?

i will try the psu on it's own now.

pictures may come if you want them (it's a mess)
 
There is definately a short circuit for a load. If you are trying to get plus and minus power supplies, a single bridge rectifier will do fine. Do you have a fuse on the primary side? Are there fuses on the secondary side? This will tell you right away if there is a problem without damaging the transformer. Use slo-blo fuses when using inductive loading (i.e transformer primary).
 
thanks for the quick replies, it is one of the secondarys, i will add fuses on the secondary and primary coils when i get a new transformer. for now, have a look at this pic (sorry about the size, i took it on low quality)
 

Attachments

  • transformer.jpg
    transformer.jpg
    59.6 KB · Views: 339
maybe a short in the primary side of transformer...
it hapen to me in Kora Hibride...the transformer became very hot...but i have find that was two turns touching...i pull them apart put some vernish...and it riturns working properly...;)
I' m a lucky man!!!
But if that is not your problem you may check for oscilation in that chanel..or short circuit!
Good luck!
Regards
Jorge
 
What is the manufacturer and model of this transformer? Does it have a shield wire? It looks like it might but I cant tell. If so this should be attached to the star ground point. What are the wire color codes for your transformer? Typically orange and white are line neutral, black and brown are the line, there are some normal colors for the secondaries too but I will not speculate. If the two dot ends or the non-dot ends of the seconaries are connected, you are driving a short circuit. On the secondaries, a dot end and a no-dot end should be connected and become the common line to be attached to the star ground point. This may be what caused your problem. An idle transformer should dissipate little heat.

BeanZ
 
The colour code is right actually. The transformer is from RS right?

Then blue/brown is mains

Black/red is one secondary
Yel/Orange is the other secondary

looks like one of the secondarys have been shorted (internally or externally) and has melted all of it's insulation.

safest thing to do is to replace the transformer

BEANZ : don't forget mains colour coding is diffrent in UK then US