hifi engine

Replacing burnt transformer

I have a Pioneer SX-780 with a burnt power transformer,I have a new one...How difficult is it to replace ? Seems pretty up shuck...to do myself ?

Re: Replacing burnt transformer

Hi kurbkrawler,
I borrowed an idea used by tube-tv techs when they fired up a set after repairing:find a way to put a light bulb in series with the power cord and rate the light bulb at or slightly higher than the fuse rating. 100 watt for 1 amp,etc. Max.300watt bulb. Locate the bulb via jumpers or extension cord to a well insulated area. Shade is a must. The idea is to limit,not cut,the current in case of a short. Just may buy some time to do a shutdown before damage is permanent. Start with a small wattage,and graduate up,if needed. Remember,the cold resistance of a filament is several ohms. A transformer is a reactance device(current and voltage out of phase) and responds differently to the addition of a nonlinear resistance. With me so far? It works so well,I use them to track down overloads in commercial dishmachine wiring,which is my day job. SAFETY FIRST! Check all connections before applying power. Live long and have fun doing what U love to do.

karodimitrov's picture

Re: Replacing burnt transformer

Take the camera made several pictures of the outputs of the transformer. Which color goes where. Then get out the old and put the new one. Color by color soldering and ready. It is easy.

Re: Replacing burnt transformer

Be careful, transformers don't usually burn up by themselves. They usually burn up because someone jumpered across fuse or put in a value way higher than the spec. And many times the short that causes the overcurrent and transformer burning is found in the output stage, or the power supply.
so you need to look and check for shorted output stage, or shorted rectifiers, or filters in the power supply.
If you still have the short, and the fuse is a lot higher than the rating, you can easily burn up the new transformer.