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Think this is repairable?? ZX475 blown transistor

Posted: Thu Mar 10, 2016 11:34 pm
by bikergreen
I picked this thing up on ebay as not fully working, it looked good cosmetically.. When I received it I opened the box and smelled like burning.. bad sign. I opened up the amp to take a look and well, one of the transistors went off like a bomb! I've powered it up and both front channels work and sound good. The left rear channel is the one now missing a transistor and the RR channel works but is a bit distorted, which I think is caused by the gain pot.

Looking for some thoughts of if you guys think this is salvageable, that being said I may give it a go just for fun. I'd need to source a transistor and replace a bunch of resistors and make some tracks to replace all the burnt up ones.

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Re: Think this is repairable?? ZX475 blown transistor

Posted: Fri Mar 11, 2016 5:58 am
by Eric D
That can be fixed, but it will be quite a bit of work.

Re: Think this is repairable?? ZX475 blown transistor

Posted: Fri Mar 11, 2016 8:37 am
by bikergreen
Eric D wrote:That can be fixed, but it will be quite a bit of work.
That was my thought as well. Hoping to get some tips on steps and what else to replace etc. I have the ability but don't know enough about PCB repair.

Re: Think this is repairable?? ZX475 blown transistor

Posted: Fri Mar 11, 2016 12:08 pm
by Eric D
-Remove any bad parts first
-Clean the board as best as you can
-Take photos of the area
-Cut out the bad part
-Make a patch using raw copper clad pcb, and the photos you took

If you don't know where some traces went, others on this forum, may have amps they can help you get information from.

Re: Think this is repairable?? ZX475 blown transistor

Posted: Fri Mar 11, 2016 11:10 pm
by Mr. Wild
Obviously that 8 fet power supply can deliver some serious current! Even the buss bars are warped from the heat :shock:

Re: Think this is repairable?? ZX475 blown transistor

Posted: Fri Mar 11, 2016 11:30 pm
by vwdude
That looks very familiar...I had an amp with very similar damage. I repaired it and it tested fine for me but when I sold it the new owner had issues so he ended up scrapping it.

It's a worthwhile amp to practice on. If you have luck fixing it then you'll have a great amp, if not then at least the case is salvageable. You can find a rusted out amp and take the board for your case and voila, a good amp again.


Check out www.phoenixgoldregistry.com

Re: Think this is repairable?? ZX475 blown transistor

Posted: Sat Mar 12, 2016 5:42 am
by trickyricky
Give it a try....if you fail don't worry or get bummed about it. Scrap it, I would be interested in the xover board for sure as I need those hard to find RCA's. The case is also neat to keep, nothing is trash.

Re: Think this is repairable?? ZX475 blown transistor

Posted: Sat Mar 12, 2016 10:09 am
by bikergreen
trickyricky wrote:Give it a try....if you fail don't worry or get bummed about it. Scrap it, I would be interested in the xover board for sure as I need those hard to find RCA's. The case is also neat to keep, nothing is trash.
Ya thats what I'm thinking, not to worried if it doesn't work out as I have another one coming ;) - have plans for the case and other things already. Fun to take it apart and experiment.