Onkyo SKW-591 subwoofer is dead

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

The +/-12V components are visible like R912/D912/L912 same for the other side R911/D911/L911, C921/C922 are on the other side, but I can't see anything else.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

The 8C is the (NJM78L05) Q435 the other one that looks the same will be Q436 and have a 9C (NJM79L05)
The only other thing I can think of that could cause that -12 to be high is that C912 is bad, as in almost open, find it and solder another 10µf/100v across it and see if the voltage comes down.

D922 was showing .76V same as D921.

that could be misleading as these are zener diodes and even though it checks ok could zener at a wrong voltage. But like I said if it did zener at -9 instead of -12 the supply from D912 would be lower, not higher.

And the -12 being -9 might not effect the operation that much as it is only the supply for Q301, so it might effect the auto on function or the audio through q301.B might be a bit low or slightly destorted but should not stop the sub from working.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

I have removed both C911/C912 and both show 10.2uF 0.42ESR, with the Chinese component tester.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

When you mesured those voltages, did you have audio going to the input? It might be that the voltages were off due to the state of the switching power supply, It was likely in standby.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

It was in standby. I just plug it in and measure. I can hear a slight high voltage whistle coming on. Speaker is not connected either.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Unfortunately I don't have 10uF/100V capacitors, only lower voltage ones.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

With the sub in standby, only the switching power supply will be working and at a very low power, so those other voltages might be off. since none of the other circuits are drawing current, that cap may have charged to a higher voltage. once the sub is turned on I suspect it will drop and the -12v will be normal.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Found the 8C and 9C. These turn on only, when there is a signal right?

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

Not really, Its the transistor before the input to the regulators (q433/434) that turn on with signal and supply the regulator's input.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

I'm about to throw in the towel. I don't even know from where to get the ground from, when I take measurements.
This thing is not worth $40.
Now I have 38V, at the speaker output.
At 7905 I have -4.99, but nothing at the 7805.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

If you look at the schematic you will see where the ground is. That large black ground line that connects to q501 pin2. There seems to be only one voltage that does not use that ground, that is Q501 pin 12 vcc, It uses the minus of C503 or the minus of C902. If you follow the VCC (Q501,Pin12) it goes through R528, to VB Q901 (78M12) This 12 volt regulator has it's ground connected to -B so to measure THIS voltage you would just measure across C907.
If you used the normal ground to check this voltage it would not show correctly, it would likely show around -30 volts.

If you don't have VAA +5volts that will throw off the bias of the whole amp circuit so you will likely show a high voltage on the speaker terminals.
Again just look at the schematic, +40 comes to R433 and connects to Q433 emitter, this transistor acts like a switch, R435 should be low on the end opposite the transistor. If the transistor is turned on you should have ~10 volts on the input of Q435 and +5 on the output.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

I can't find Q433 and R433.
I have removed 7805 and installed a regular big one in there. At the input I had 5V and at the output I had 4.3V. Something is not right, it should be higher the input voltage.
Course, I must of made a short because I blew up Q502.
I have decided to put back the original 7805, to compare the readings. I have ripped off the input trace, so the smd 7805 I had to solder in a bit crooked, to be able make contact each leg. Most likely that caused the short.
Tomorrow I will look into it, what happened. Before, the output it was 0V, so I'm guessing, that the original 7805 is open.
Can I diagnose this amp, without Q502 soldered in?

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

Yes you should be able to operate the sub with Q502, I suggested it in post #3
R433 should be there, I saw the[*] beside it and was'nt sure, but looking at the chart at the bottom of the schematic indicates it should be there and the value for different versions. 1.2k 2 watt will not be a small resistor. I wouldguess it is mounted on the other side of the board. It might be mounted closer to C901

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Oh wait, it's most likely a big resistor on the other side. Damn, I was just searching on the bottom. Thanks R_J.
Without Q502, how it will affect the speaker output? You know, when I want to check the output voltage.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

You won't get any audio out but I suspect the speaker voltage should be near 0 volts, I could be wrong, It's hard to say how the ciruit will act but I can't see an issue.
The audio drive signal comes from pins 11 & 14 of Q501, so with out Q502 there will be no audio at the speaker.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Both R433/R434 are big resistors on the other side, and they have the right value.
Q502 had a short between pins #14/15. I have replaced it.
I have placed an order, for new amp ICs and some 7805V regulators.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

Q502 only has 5pins so I guess you meant pins 4 & 5 or did you mean Q501 pin 14 & 15?

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Q501, you are right.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

The parts have arrived, and of course I have purchased the wrong package(to big).
I have soldered it in somehow, and now I have +/-5V now. Speaker still shows +2V, without final IC.
I will solder in the final IC, and see what happens.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

You could check the voltages on Q501 and see what they are but looking at the ic' pdf the voltages on the output side seem to be referenced to com (pin 10)
I'm not sure why there is +2 volts on VS, it could be coming from Q501 or it might be normal, there is a difference in resistance from VS to positive supply (42.1k) and VS and negative suppply (44k) and that might explain the +2 volts