amp repair fets?

[sqguy 0]

Ok I'm not that good at this but have a newer amp with 6 chips on the PS sink. Seems to be two transformers and 3 fets each, the output is on other side of chassis. Well the 3rd and 6th one are shorted pos to neg and blew the +12v trace. If shorted then they must be bad, the rest are near same ohms and not on/shorted at rest and all same # chips. Anyway, can I just replace them....what would cause this to happen? Would something else be shot too? They are $15 each so far I've found. Yes this is a junk explode amp, but might as well see what I can do its like new otherwise and 500wx1rms so not bad. I've been told not to substitute parts on new amps, have no idea what was done to it when it broke. Amp is worth about 100. Amp has no power, light comes on and thats it, has 12v in transformers and thats about it less than 2v in rails.

Edited September 26, 2007 by sqguyib

[JimJ 11]

If you can find compatible replacements, and you want to save the amp, I don't see why not.

[sqguy 0]

This is part: http://221.253.80.196/en/prod/semicon/pdf/data_ekv550e.pdf

Naturally I don't want to have $30+ship into it if that kind of failure would usually have other issues to repair that I'm not capable of. Nothing looks like it got hot but I don't know what would cause this. I guess two 40a fuses do not protect much...doh, or maybe it's a fault in design.

Sony will repair for 100, you can buy a refurb for 100...in fact the refurbs are all over the place so this must be a fine amp...but figure it would be a good little project instead of trashing it. Have no idea how well they work, I'm not super impressed with my Kicker so far but since the whole system is new I can't call out the amp alone...but they seem to be in the same price range as this Sony. Kicker does work ok, just wish I would have wired it up to my old drivers for comparison. Also it really drops power with the car off.

[X-OvrDistortion 0]

This is part: http://221.253.80.196/en/prod/semicon/pdf/data_ekv550e.pdf

Naturally I don't want to have $30+ship into it if that kind of failure would usually have other issues to repair that I'm not capable of. Nothing looks like it got hot but I don't know what would cause this. I guess two 40a fuses do not protect much...doh, or maybe it's a fault in design.

Sony will repair for 100, you can buy a refurb for 100...in fact the refurbs are all over the place so this must be a fine amp...but figure it would be a good little project instead of trashing it. Have no idea how well they work, I'm not super impressed with my Kicker so far but since the whole system is new I can't call out the amp alone...but they seem to be in the same price range as this Sony. Kicker does work ok, just wish I would have wired it up to my old drivers for comparison. Also it really drops power with the car off.

You would be best off replacing all of them, at least in my experience that is the way it should be done.

If you look hard enough, you should be able to find them for around 3.00 per chip. You should be able to cross reference them and find a cheap one.

[sqguy 0]

It appears to be a sony part 655144901 and that is why its hard to find. Does not cross to anything on sites I found and can't find a place to look up by specs yet. I have found a bunch of posts saying not to substitute on factory parts like this, naturally.

I imagine putting all of them in would be the right way, but 15x6=$90 and I can near buy one for that and might as well toss it. Let me see if I have a pic of it, there are not very many parts in there. Here is an ebay, item 170152581038

[sqguy 0]

OK found some cheap with some help from a guy...that sells them of course. This one looks real close in spec to the original, the timing is a little faster (tr, td, tf) is all but not sure that matters or not...other specs look good. So, we will see. I will go at it when they get here and see if I can un-explode the explod.

We'll find out if I'm the dude on the left or right there....

[sqguy 0]

Got rolling here and replaced all the fets, checked them, all was good. I hooked it up to a junk lawnmower battery with a 2amp charger on it, enough to run it at 12v. Ran off an old HU and to a couple of 8ohm bookshelf speakers. It worked but all is not well.

The heatsink on the far left got pretty warm but I could still keep my hand on it. I had unhooked the RCAs and was looking at the voltage to the speakers to see if both channels were the same, they were close. Only played it at real low volume for maybe half a minute. It then killed the battery and I noticed heat so then unhooked it. There are two tiny white pots in the left center of the board and I turned them checking for shorts way back....put them back but they could be off a hair. Have no idea what they are for naturally. I turned one and it did change voltage on output. Also on the warm sink I found two of the chips look a slightly different color, the metal part is more reddish but who knows. Was going to check ohms on all those but needed a break. I figure either I screwed up some adjustment there, or that output is screwed and might have trashed the power supply in the first place. Nothing else got warm at all...no new smoke yet...lol.

The two old fets are completely shorted that were bad, the others are not. The gate resistors all showed the same ohms and looked fine, they are the tiny things. I'll check the output chips now but will have to research to get beyond that. Was reading about differentials the other day but didn't finish that. Didn't think to test rail voltages when it was up.

[sqguy 0]

Checked the outputs best I could, nothing looks bad and they all test the same. Since it worked, I'll guess the bias is off and heating them up. I read under 15mv but I'll have to find a manual or tech to get it set right. Someone could have messed around in there before me as well. This must be humorous reading for somebody....

[JimJ 11]

I admire your tenacity

[sqguy 0]

I admire your tenacity

I'm not really sure why I decided to fix it....maybe just doing my part to keep something out of the landfill; to keep the world green!!!! Yeah that's it! lol!

If it really is 500wrms it would run my subs fine if I ever needed it, just not sure I'd want it in my trunk.

[sqguy 0]

Hmmm, something else must be amiss with this high powered $100 amp. I checked all the o/p fets and none are shorted and the diodes seem to be working. I ran it again and it plays fine, but the one channel still heats even playing nothing. Checked rail voltages and they were +/-48v. Not hooked up it shows 2.6mv on one channel and 1.6 on the other, .8 on the other two I think it was. So I cranked the bias down on the high one that is heating and it would not drop under 2.4, but would go higher. Have to research more, but maybe some of the fets are bad. If I get the ambition I'll take them out and test more but that sounds too easy. Showing same ohms on output resistors also, they are .22ohmK. Can't remember if I checked the gate resistors, think I did. Strange that it actually plays music though, and both channels sound the same....gives hope I don't like to have with these kinds of projects.

[sqguy 0]

After much screwing around/testing it seems that it might be ok. The bias was high enough to heat that side, though I don't know why it would be so off with only power supply repair....but it was and now I know how to set an amp bias. It still has higher mv on one channel at rest, but could be normal. Have it set right now and it plays with no heat, well both channels heat a very little after 20min of low volume playing. So I'll put it back together and dig my spare sony 12 out of the shed, see if I can hook it to the car. Didn't cost me much at all (if it works under power) but sure was a lot of screwing around.

[sqguy 0]

It seemed to work fine, though it is like Dual amps in that my old 2v test HU can't run it up that hard. But I did get the sub banging around good for a while then ran regular speakers with it....worked fine. So I sold it Didn't make much but learned something and fixed a few more amps with simple problems. Well it did fill my car with gas, that is pretty good deal these days.