sony x-plod XM-1600GSD 1200W (protect mode)

[scampo77]

i have checked all of the transistors that are bolted to the heatsink and they all seem to be fine

i have not pulled the rectifiers yet because im not sure if this could be the problem and also im not sure how to check these.

any suggestions?

[Glowbug]

Going into protect no matter what the impedance is?

[scampo77]

sorry its going in to thermal not into protect. there are 4 LED lights power, over current, offset and thermal.

even with all of the FETs out its still does this.

[scampo77]

im still new at this and i cant tell which FETs do which job but i have 6x SSP45N20A and with the diode test none of them have any shorts but all 6 test to .480. is this close enough or should i change them?

another thing i am seeing for the first time is when i am pulling the fets out (with no power to the amp) im getting a lot of sparking when my soldering iron touches on 2 of the legs. is there a way to get rid of this voltage or is it a big deal?

[Perry Babin]

It's unlikely that you'll be able to find replacements for those outputs (45N20A). Most of these amps will only work with those transistors and many of the NOS 45N20As I've found wouldn't work properly. Reinstall them if they're not shorted.

The rail capacitors are remaining charged. Either wait until you read only a few volts across them or discharge them (preferably through a dummy load). Soldering the FETs in with charged caps could definitely blow them.

The 'outputs' will have a direct connection to the speaker terminals (assuming there is no speaker protection relay). The 'power supply transistors' will have a direct connection to the primary side of the power transformer and to the B+ terminal (when checking for continuity with your multimeter). The connection is typically to the center leg of the PS FET but on this amp, the connection is to the third leg.

[scampo77]

do you have any advice why the thermal light keeps coming on?

[Perry Babin]

Post the DC voltage on all 14 pins of the LM339. Place the black meter probe on the amplifier's ground terminal. Place the red meter probe on the point where you need to measure the voltage.

LM339
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:

[scampo77]

is it normal not to ba able to get transistors to repair amps? if so which amps should i stay away from?

[Perry Babin]

Some amplifiers only work properly with the original transistors. There may be other transistors that are drop-in replacements but finding them can be very time consuming and expensive. Sometimes, you can get substitute transistors to work but it requires a bit of re-design to get the amp to work properly. The amps that use the SSP45N20A are the hardest to find replacements for. For amps that used the 45N20A and have less than ±70v rails, the IRF3415 is sometimes a good replacement. I used lots of them in the MTX 6500Ds. For amps like the Sony P5 amps, the MTX1000D, MTX81000D and some Xtant amps, finding replacements is more difficult and all that I've found required at least a bit of tweaking for them to work properly.

Confirm that pin 12 has 6v. It should be at 0v. If it's at 6v, look for open ground traces.

[scampo77]

it was at 6v and i did find a open ground trace i bridged it and now the voltage at that pin is 0 but the light is still on.