Transformer Fix?

[tom.ad...@gmail.com]

Hi, 

Would anyone be willing to help me fix a Bose mains transformer?  I've not done much electronics work before but am keen to learn.

Any offers welcome/or advice to get a pro to look at it!

Thanks, 

Tom 

[Simon Howes]

Repairing a transformer can be a fun and rewarding experience though its unlikely to be cost-effective nowadays unless said transformer is quite specialist and rare. The reason for this foremost is that the copper windings if removed must be replaced - you cannot rewind them as the enamel coating becomes embrittled over time/usage and will no longer be insulating. Unfortunately copper makes up most of the cost of motors/transformers nowadays, so you'll find replacement wire very expensive. Ebay may be a better alternative...

I'm guessing this is for something like Bose receiver? They tend to use toroidal (donut!) transformers which are really fun to tweak because they have their secondary windings on the outside (the mains windings are encapsulated inside epoxy on the inside). This allows you to adjust the voltage by counting the windings and then taking off or adding windings (something I did for a cnc mill once to get within 1V of the 35V max of the drivers, but I digress!) :)

you probably want to put a multimeter/ohm meter over the coils and get the resistance. This will tell you which one is blown. The input should have a high resistance and the output a low. If the meter doesn't read you've found the busted coil. If its the primary (mains/high voltage/high resistance) winding which is cooked and the transformer is a toroidal then you're out of luck, as that winding is sealed inside the insulating epoxy and you cannot get to it...

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[Paddy Duncan]

..unless he means the PSU :)

Paddy

[Philip Roy]

Many small mains transformers have a thermal fuse bound onto or into the windings, it is always worth checking to see if this has failed, like ordinary fuses they sometimes just die of old age. Replacements are about a pound each. Fitting usually involves judicious use of a scalpel to remove the old one and a couple of small cable ties or a bit of epoxy to secure the new.

Phil

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[Tom Hayes]

Thanks for the help.

All fixed - luckerly once I got into the transformer (which was the hard bit - they dont make it easy!) it was just a loose connection - phew!

T

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