Blown sundown 3000d

Have a blown Sundown 3000 Im trying to fix for a friend. He ran it at 1/8th ohm (.125) and it blew in short order.

OK, so far what Ive figured out.. a few power supply fets are burnt, and a few output fets look OK but measure shorted. Going to replace all of them except the 2 fets in the middle on each side which I believe are voltage regulators right?

So, besides replacing this obvious stuff

2 output drivers IRS21844STRPBF
12 output fets IRFP360LCPBF
16 power supply fets IRFP064NPBF
All of the power supply gate resistors (red/red/black/gold) 22ohm 5% tolerance right? What wattage rating should I get? Resistors are confusing to me.

The output gate resistors all *look* okay and I will measure them once I pull the bad output fets but Im pretty sure they are OK.

So, besides the stuff I listed.. what else should I check or replace? Where are the power supply fet drivers and what would they look like? Is it a big IC? I see a KIA494AP.

The power supply driver transistors may have the circuit board designations of Q7-Q7C and Q8-Q8C (not sure, I don't have any specific information on this amp, a photo of the board may help).

The gate resistors are likely 1/4w. Measure them and buy resistors that are the same physical size.

The L7812 regulators commonly fail when the driver ICs fail.
These arent photos of the amp Im working on, I found these online. Hopefully they help.



If you click them they should expand.
OK I think I found them.

Q17, Q27, Q47, and Q49. After some searching I found that they are "2sa1023" but I cant find them for sale anywhere. What is a suitable replacement that is more easily available? Each one goes to 4 power supply fets.


They are circled in green.

Theres another transistor closeby though that I dont know what it does. It is a "2sc1027". What is a suitable replacement for it that is readily available? Might as well replace it too. Its board designation is Q18.

What is the thing circled in orange? I know its a terrible picture, but it is a bigger 3 legged thing. Its board designation is Q24. Says KAY 1381 on it. Should I replace it as well?
If the A1023 transistors are defective, they can be replaced with BD140s.

Q18 and 24 are part of the protection circuit. It's extremely unlikely that they have failed.

Q30 (a KTD1302) may have failed. I don't have any suggestions for a substitute. I doubt that it's critical as long as the transistor is high gain and rated for at least 300ma.

OK thanks for the info. Did you get my email about the pad that I pulled on the audio board? :eek:
CRAPPP! I pulled another pad! Ive replaced these IC's on this exact same amp (well this particular model) before with no issues, not sure whats going on. I didnt even know I pulled this one until I looked later.

This one is the opposite corner closest to the corner of the board as well. Heres a crappy picture.


Please tell me this one isnt used for anything either! Board is a DWM3640, can someone confirm neither of these pads are used?
The datasheet shows that 8, 9, 10 and 14 are unused pins.


Didnt even think about checking that.. DOH. I see that in this diagram. Dont really see a notch in the top of my chip like in the picture, but if that notch indicates the little dot thats used to orientate the chip correctly... then I think I got lucky. On U1, I pulled the pad for pin 8, and on U2, I pulled the pad for pin 14. Thats more or less a miracle......

I got all 16 of the power supply fet gate resistors pulled as well as the power supply transistors. Going to replace the resistors and replace the transistors with the BD140s as you suggested. Not replacing the output gate resistors, they seem to be OK. The outputs didnt have a bad failure, I guess the power supply went first.

So the list of stuff getting replaced is...

2 output drivers IRS21844STRPBF
12 output fets IRFP360LCPBF
16 power supply fets IRFP064NPBF
16 22ohm 1/8w power supply gate resistors
4 power supply transistors BD140

Really hoping that fixes it.. since I dont really know what to do past replacing this stuff.. and the fact that its not mine, its a friends.. just trying to help him.
The unconnected pads tend to lift easier because there is no trace sinking heat away from the pad. This means that they get hotter than the other pads.

Oh ok. That would make sense. Ive just never had it happen before on one of these boards. Little ICs can be tricky to get off though because theres 14 pins.

Would you suggest replacing anything else besides what I listed 2 posts up?
Wanted to update this. Got all the parts in the amp and it is working great now!

Bad news, me and the same buddy who owns this amp, decided to slap all of the 3ks we had in just for giggles. He had 2 wired to .5 ohms each, and wanted to try 4 at 1 ohm each.

3 amps were his (one being the repaired one) and 1 was mine. Of course, for whatever reason, mine blows.

Power supply went. Same amp, same parts. Hes not sure what happened but is paying for the parts for me to fix it. Outputs are OK, few power supply fets failed pretty badly. Going to replace all of them and a few gate resistors and the power supply transistors and it should be good to go.

Thanks everyone for the help.
When you get it repaired, confirm (with a scope) that you have a good drive signal on every power supply FET. Touch the probe to the leg of the FET.

Also, with the amp is on but no load and no input, push/pull/twist the transformers. Also push on various parts of the board to see if there is a change in idle current. If there is an intermittent problem, it should show up.