Power supply torrid/transformer

[o. l. t.]

This Ample A226 was being used by a guy that seems to have blew it and pawned it off in a trade which I eventually got the amp and now would like to ask about a repair on it.

The main power supply torrid has a burnt winding. It doesn't go far, but apparently far enough because it blows the transistors in the power supply after coming on and playing for about 8 seconds, then politely kills (2) twenty amp fuses in the process.

The transistors in this power supply are NTE2396 and are getting pretty pricey from the local electronics shop. If I am going to keep blowing them testing this amp I'm going to have to find some bulk.

My question is this..... If the coating is burnt off the wire and that is causing a short in the transformer torrid, can I peel back that one winding a little bit and stick some shrink wrap on it or something else to make the torrrid useful again?

[Perry Babin]

NEVER use NTE parts in car amplifiers. Their ICs may be OK for TV repair but their transistors are essentially useless for car amps.

Buy some nice cheap IRFZ44s to repair this amp.

If there's enough wire and no other underlying windings were affected, you can insulate it and it should be OK. It could be completely rewound but that is time consuming and likely not justified for this amp.

[o. l. t.]

I am missing a section of one wire. From what you see what is the easiest way to fix this to make it work?

This is two winds around.

[Perry Babin]

You can solder a piece of wire to the short one.

[o. l. t.]

Should I use stranded awg or try to find a piece of solid copper?

[Perry Babin]

Either will serve the purpose. If you have an inductor from a passive crossovers, it may have suitable wire.

[o. l. t.]

My goal in doing this would be to get that wire back to length, then perhaps use shrink wrap and isolate this wire cluster from the other wraps, then I should be fixed, yes?

[Alaraune]

Hi! you need rewind the toroid, check the turns of burn wire, then, rewind the toroid with new wire. You need new wire, sorry, but is necessarily.
Sorry my bad english.

[1moreamp]

Shrink wrap is a bit thick, but if that's what you have then go with it. remember windings on a toroid don't usually have insulators between them as it interferes with design and causes other magnetics issues. Since your close to the end of the windings the issues might not rear their ugly side and cause any troubles. I myself am fond of kapton tape and insulating varnish. Both of which are very thin and flexible and can withstand very high heat before failure.
You can search for transformer tape it comes in several forms and thickness's but this most likely is going to cost way more then varnish and simple kapton tape.

As for the finality of your repair well in my mind I am hoping the bad wiring your fixing is all the bad spots as some can be hidden under windings and not accessible unless the toroid is completely unwound. I have my fingers crossed for you though...

[ppia600]

+1, I've NEVER had any luck using nte mosfets, and especially wouldn't expect them to survive long in a parallel setup. That may even be why the transformer is toasted... because the guy who originally "repaired" the amp used the nte's.

Originally Posted by Perry Babin

NEVER use NTE parts in car amplifiers. Their ICs may be OK for TV repair but their transistors are essentially useless for car amps.

Buy some nice cheap IRFZ44s to repair this amp.

If there's enough wire and no other underlying windings were affected, you can insulate it and it should be OK. It could be completely rewound but that is time consuming and likely not justified for this amp.