Hey all. I recently purchased a non working Memphis 500D from fleabay and obviously, it doesn't work. It was "blown" before and it look like most, if not all MOSFET's have been replaced. The problem was it wouldn't turn on...at all. Then, after looking a bit, I found that a capacitor was missing (upper red arrow). Unfortunately, I had no clue as to what size and rating so I guessed. I used what little knowledge I have and tried a 100 microfarad 35V capacitor. Now, the amp will attempt to turn on, but only the protect light will flash for a second. You also hear a click when the amp has power and then another click when the power is removed. Also, the two MOSFET's indicated by red arrows at the bottom of the board get really hot while the others just get warm. I used new thermal paste when I reassembled but the original owner did not. Could they have severly overheated and are causing a problem? Could some of the FET's be screwed? Could I be waaaaaay off base on the capacitor that I chose? I tried testing the FET's but I have no success. My good meter has a blown resistor on the impedence side so I only have a crappy meter to use for the time being and I just can't seem to get anything conclusive. Anyone have any ideas? I need some experienced electronics engineers, here. Thanks and sorry for my long post. Here are the pictures: (note, not my soldering)
EDIT: in the pics of the FET's on the lower portion of the board, the far left FET is missing. That's because I removed it to attempt testing but it is now back on the board.
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That board is butchered and fried man, Even if you do get it repaired, I doubt it wil be what it was. Your best bet is to sell it off threw egay, or trash it.
My Cav
I give up...
i'm buying a VW those people love trees, so they should love eachother too... "Andy"
that things toasted. you've probably got some layer separation, as well as some trace-burns. the soldering job isn't that great either. looks like several cold-solder joints. one of the resistor's don't look to be in that great of shape either.
I can't tell too well from the pic, but it looks like the cap is missing on purpose. they could use that board for several different products, and in that model, that cap isn't used.
I would say to remove all the FET's, clean the board thoroughly with some isopropyl alcohol and do a thorough inspection of the pads with at least a 5x jeweler's eye loops to look for damage.
or just get rid of it. sorry man.
Desert Tuners
“When you come across a big kettle of crazy, it’s best not to stir it.”
you definately have some solder skips and bridges there with that bad solder job....could have been why it fried in the first place
Yeah, the guy I bought it from said he took it to a shop and had it repaired....shop? Shenanigans. I think he tried fixing it himself and it didn't work. I believe it can be fixed no problem (I've seen worse fixed) but it's just more than I want/need to dive into. I've already relisted it on fleabay, hoping to recoup what I paid. On the bright side, I did pick up a working (supposed to be, anyway) Rockford bd500.1 for $120 and change.
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Wow, wish I had known about them before I listed it on ebay...it would've only been $80 to fix. Ah, well, the Rockford will do, I guess. Thanks anyway.
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Just for a heads up, the amp sold for $35...woohoo I made $3.00!!! Stupid amp...
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