Replacement part number for black transistors in the 2125

[Lance_S]

Hey guys,

I just smoked two of the black transistors on my 2125. They are the ones that are in a row of 6. They are slot number 0304 and 0306. The first and third from the back on the left side of the amp. I am hoping digikey has replacements.

Are they difficult to replace? Any advice is appreciated.

Thanks,

Lance

[Eric D]

If you smoked those, I highly suggest you replace all 6 on that side. If you don't any of the other 4 may soon fail. You probably also need to replace the fusable resistors connected to those transistors as well.

[Lance_S]

Eric,

Ok. It looked like the first 4 are irfp044, the last two 16JPF20 and 16CPF10. Can I replace all six with the same units or do they need to be different? Also, what about the resistors, looks like there are 3 of them. Do you know what the model numbers are for the parts I need to replace?

Thanks for the help.

Lance

[Lance_S]

Some before and after pics. It was only hooked up for about 3 or 4 seconds. It was my fault. When i was buttoning up the reassembly I failed to screw down the board ends of the power rails. I didn't notice they weren't down because they were laying flat, or close to it, on the board. But the two small screws weren't in and down. Lesson learned. Anyway, just wanted to give you a pic, they always help. The board cleaned up pretty well, doesn't look like any permanent damage but would appreciate your input.

Still need a place to purchase the replacement parts if you have any ideas.

Thanks,

Lance

[Eric D]

OK, this changes things. Those are in groups of 4, the end 2 items are rectifiers, not transistors. You need to replace the 4 only. If the other 4 across the amp are bad, you would need to replace those as well. The resistors near the transistors may have failed as well.

[Lance_S]

OK, that's what I thought. They had different numbers on them.

Here is the link for the transistors. the numbers match up. Do they look like a proper replacement to you?

http://search.digikey.com/scripts/DkSea ... 044NPBF-ND

The other side of the amp looks brand new, no smoke, nothing. They all look great on the other side.

Is there a way to check the transistor to see if it's bad without swapping it out?

Thanks again Eric for all your help.

Lance

[Eric D]

Those look to be the correct transistors. Were the ones on the other side not bolted down as well? If they were not, you can probably count on them being damaged.

A DMM (digital multi meter) in diode check mode can tell you if the transistors are bad. It can also tell you if they are bad while in the circuit, but it will not rule out them as being good while in the circuit. However, it seems that 90% of the time if they measure good in the circuit they are actually good.

[Lance_S]

Yes, the other side was bolted down tight. But the left side of the amp was the only side that lit up. The right side (the other side) looks perfect, no damage.

I have a DDM. I will check them out and see what it says.

Thanks again for all the help.

It looks like there is a solder connection on both the back and the front of the transistor where it goes through the board. Is that your take as well? To pull them off my plan is to wick the backs of them, then flip them over and wick the front. That should lift them off. Any added advice on tricks to pull them and or install them without damaging them?

Thanks again for all your help, couldn't do this without your expertise.

[ttocs]

I always recomend a desolderer for that. IT has a hot hollow tip and a rubber ball on the end. all you do it gently heat the area, suck out the solder with the ball and it will fall out. They are only $15-20 at that rat shack.

[Eric D]

To remove the bad transistors, I just cut their leads, then heat up each remaining lead still in the board, and put it with some tweezers. It is pretty hard to damage the board this way. If you try removing a burned transistor in one pieces, you are taking an unnecessary risk at damaging your board.

[Lance_S]

I learn something new on this board daily. Thanks, makes total sense. cut them, heat them and pull them individually, got it.

Do you suggest soldering both the front and back of the joint or just the back like we do on the caps?

[Eric D]

PG soldered just the top at the factory. I mount the board, then bend the leads trim them, and mount the devices completely without soldering. Then I solder them from the top. When all done I remove the board and solder from the bottom as well. This is a good way to make sure the connection is good, and to make sure there will be no stress on the leads when the board is mounted back in the heatsink.

[marko]

just like Eric says, on all ms/mps and mq amps the board must be fitted and screwed down in place before any soldering happens, if not the fets will not seat correctly to the sink and will burn up within minutes of playing..

[Lance_S]

Good stuff, thanks guys. That's what I will do. Just ordered the parts from digikey today, should have them by Monday.