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I blew 2 transistors.The markings on them are nl720 MTP 50N06v that what it looks like. Both channels blew. One channel melted the transistor the other transisitor cracked and fell apart. Where can i find some transistors to replace these with? Also i dont know why it blew. I was bassing for about 10min(on my way to return something) and when i turned my truck off i went to the passenger side to get a box out, and noticed smoke. It has blown b4 after i shut it off about a year ago. While its on it works good. Its just when i turn it off. The time before it was 2 diodes that i looked like safety diodes. Now i wish i replaced them instead of just taking them out.
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They look like transistors, but could possibly be something else. It is a T-220 case. and apperas to have one leg connected to B+ input. It looks like it has the motorola symbol on it, but its so small it hard to tell.
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They are MosFETs, and probably are from Motorola. You say you blew both channels, do you just mean you blew both of the FETs? Are the FETs closest to the battery connection or the speaker connection? I'm guessing since you said they are connected to B+ they are the power supply FETs. You can just replace them and it may work again, but you need to find out why it happened so it doesn't happen again. You can get replacements from www.mouser.com that would probably be the easiest place if you don't have a local electronics store. When I get home I'll take a look at one of my RF amps to see if I can come up with any reasons for the problem.
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ON Semi is the division of Motorola that does discrete components so I'm sure they are the same thing. You could also replace both of them with MTP7060 or RFP7060, they will have a little more current capability. It won't help if you have a major problem, and it won't make more power but it is a little margin for error. Plus they shouldn't be any more expensive
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I also blew 2 diodes about a year ago that were reversed biased between the B+ and Ground. I had assumed it was a saftey so that if excess current or voltage was pulled the diode would breakdown and the fuse would blow. I had taken them out and did not replace them. Does anyone know the specs on these diodes or an equivalent that i could replace it with. I have lost the original diodes so i dont have any numbers off of them.
I am trying to find out what caused it to blow. I have a power 250.2 in the shop being repaired for warranty work and dont want to connect it until i find out why my other amp blew.
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I'll check my RF amps to see what they use for the diodes. Normally they are there for protection against hooking up the pos and neg backwards. As far as the power supply FETs blowing normally it is because they are trying to pass too much current because of a fault somewhere, low battery voltage, low impedance... Can you tell me more about what you were using the amp for.
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I am running 4 gauge to a few inches from my amp and runing 4 gauge up to my amp. I am pushing one 12"XLC in a 1.25CuFt Sealed Box. The box is fiberglassed internally and have about 3/4 lbs of poly-fill. I have a high to low convertor coming off my rear speakers.
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looks like the right part to me, it's pretty common in alot of amps, made by mtx and rf. as far as those diodes, they are there to protect against hooking the amp up backwads. i would just use a regular silicon diode about a 1/2" in dia., and make sure you put it in the right way.
there had to be some reason that your amp burnt up though, look at the board really close, since you've already taken it apart once check for any trransistor heatsinks touching the heatsink itself, also the screws that attach them to the heatsink. i had this problem and after about a year the power supply burnt up.
sounds like the power supply is where you have the problem since neither channel works, i would go ahead and replace all of the fet's in the power supply, since there's a good chance that the others have been weakend and will more than likely fail again in the future.
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How do you remove the old transistors that are glued down?
I replaced the transistors and diodes, but did not attach them to the heat sink. When i play at normal volume something starts to stink like electronics burning. I opened it up and everything looks good. Is this because its not connected to the heatsink yet? It never turned off, just started to smell like something burning.
[This message has been edited by Pomaikai (edited 03-27-2001).]
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Ok I replaced the mosfets and the diodes. I grinded of the old FET and glued the new one down. I put Some heat tranfer silicon between the curcuit board and the heat sink because i had rubbed most of it off on accident. I hooked it back and played it for a few seconds and it sounded good, but then there was a small pop. Now I have to replace a capacitor. Does anyone know what would cause these to blow? it is a 330uF 63V Cap and there is only one of them on the board. So im assuming the problem is before the channels split up. It looks like it is in parallel with the power right as it enters the amp. Please help. I dont want to keep replacing parts. The cap is before the toriod transformer.
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