SPL Z1X-3000D

[Dr Zeus]

I have another one of these amps in from my local distributor. The story goes that this amp was able to power and play although very very softly like the gain and other things were all the way down. I'm not sure how much water that story holds, because on my bench all I can get this amp to produce is 15~25vDC across the speaker outputs 90% of the time with the protection LED lit. 10% of the time the amp sucessfully powers not in protection but still with <10vDC across the speaker terminals.

None of the TO-220 transistors seem dimished, but the 2200uF 80v rail caps look like they've taken some buldging heat. They are not shorted, but I still pulled the buldging ones off the pcb for troubleshootin, leaving 2 out of the 5 in place which look and read well enough.

[Perry Babin]

Was there any indication of arcing under the capacitors?

You may want to pull the third one for the negative rail if the first two were from the negative rail.

Do you have both positive and negative rail?

Positive and negative regulated voltage on the op-amps?

Have you replaced Q124 and Q125 yet?

[Dr Zeus]

I pulled all three 2200uF 80v rail caps - They are buldged but not dead shorted. Only the 2 positive rail caps remain in circuit.

The amp is starting to come on and stay powered on better than before. There is no DC voltage on speaker outputs, but no audio either.

+-13.7v on the opamps. I did not check output pins.

Q124 and Q125 are half open and need replacing. Good thing I bought a bag of MPSW42!

[Perry Babin]

In EVERY amp like this that uses 10 output transistors, you need to remove the original transistors (Q124/125) and replace them, mounting them closer to the fan. Even if the problems are not associated with these drivers, they need to be replaced (unless you're the type of tech that leaves problems so that you'll get future business from them). These will ALL fail and will often damage the driver board due to excessive heating (Class D - Type 2 in the tutorial).

If you only removed 3 capacitors, there are 3 positive rail caps remaining. The other is nearer the speaker terminal.

[Dr Zeus]

Thank you Perry, This is only the 3rd maybe 4th amp like this design I've fixed, and probably only the 2nd amp which had failed MPS42 in these locations. Something told me to buy a bunch of MPSW42 last order from Arrow and now I have a few PowerBass and this SPL to fix. They probably all have this similar issue as they all came from the same operator.

Replacing Q124/Q125 seems to have fixed this amp's issues because its playing fine now, but its time to order up some new rail caps.

Thanks!