Onkyo SKW-591 subwoofer is dead

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

If the cone is extending and staying out, that is because there is DC voltage keeping it extended, there should be 0 volts across the speaker. The sub does need an input signal to turn it on (unless it has an on switch)
The brrr may be gone because the ic has failed again.

This sub uses a switching power supply so there should not be any 120hz hum coming through the speaker even if a supply cap was weak.

There are no 7805 or 7905 ICs, on the board

If these are not there, what else is not there? I will guess that if the +/- regulators are not there, where does VAA & VSS come from?

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

I will take some pictures and inspect the power supply, since one of the transistors has failed.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Here are some pictures.
Q501 and Q502, are not shorted.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

The 12V is not there anymore. Only 0.26V is there.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

The 12 volts comes from Q901 regulator, The input voltage for the regulator is controlled by Q902 (switch) Q903, turns Q902 on when there is audio input.
I will ask again, Where does Q501 get it's VAA and VSS from ??? you said that Q436 & Q435 are not there.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Actually they are there, only in a different form factor. SMD
No voltage gets to them.
I should be using pin #2 of Q501 for ground, right? It is confusing in this design, which one is the ground.
I have found Q434, but I can only assume which one is Q432. There is that white silicon, over that area. Same goes, for both regulators 7805/7905. Both transistors check out OK, and also both regulators are not shorted or opened.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

When checking for VAA & VSS, use Q501 pin2 (or negative of C901)
Check if you have + voltage on Q433, emitter (use R433 2watt)
Check if you have - voltage on Q434, emitter (use R434 2watt)
Those two get turned on to supply VAA & VSS to Q501

When checking for the +12 volts of Q901, you need to use C902 negative as ground

There are also two other +12 & -12 supplies, C921 & C922 are the test points and you can use C901 negative for ground. These two supplies should always be on (when power is applied)
The Q501 VSS, VAA & VCC will only be there when there is audio input.

I also see two opto couplers Q955 & Q954. I suspect they are for putting the switching power supply into standby when there is no audio input present.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

I should be testing with audio source?

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

With no audio input, the sub should be in standby, you need audio input to turn it on, Audio comes into p301, then to c351 and Q301, this ic turns on the amp.
C354 gets charged keeping the amp on as long as there is audio, when there is no audio, c354 will slowly discharge and after some time with no signal will turn the sub off again.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

I'm a bit confused now, which voltages should I be able to measure at this stage, without an audio input?

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

with no input (standby)
Across C905 will have around +20 volts
from ground, C901 will have +30~+40 volts, C902 will have -30~-40 volts
You will also have +30~40v on R433 and -30~40v on R434. You should have the same voltage on both sides of the resistor in standby as there is no current, there is no voltage drop across the resistors.
from ground, C921 will have +12 volts, C922 will have -12 volts

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Ok, thanks. Tomorrow, I will check these.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Across C905 there is 26V.
Across C901 there is 40V and C902 is 46V
Across C921 there is 12V and C922 is only -9.5V. Maybe here is the difference, that can be seen, at the 40/46V.
I can't find R433/R434, most likely that silicon covers them.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

I just wanted to make sure R433/434 were ok as they supply the two 7805 & 7905 regulator ic's
That -9.v volts is low, But it does seem to only supply Q301
It could be due to a bad cap on that line, check the voltages across C911 which is the positive side and compair it to the voltage across C912 the negative side, if they are close to the same (oposite polarity), then check R922 maybe it has gone higher than 4.7K, it could also be D922 zener that is bad.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

Across C911, there is 12.4V, but across C912, there is 20.7V(!).

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

I hope you mean minus 20.7v (!)

across C911 12volts, through r921 & R924 C921 is 12 volts, seems ok and very little current flow so no voltage drop.
Across c912 -20.7 volts, through r922, C922 -9.5 volts.
This tells me R922 has gone high in value. if there was a heavy load causing the -12 to be -9.5, the voltage across C912 would also be reduced to ~ -10 volts
So R922 must be bad

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

I have measured the resistance between C922 and L922 and it shows 46.8k. I can't find some of these parts.
I have measured with diode tester across C922 and it shows a correct result.

[R_J]

Re: Onkyo SKW-591 subwoofer is dead

What parts can't you find?
and what exactly would be the correct result when measuring a capacitor using diode test?

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

R922, D922
See that area how it looks.
I have lifted that big capacitor and removed that black tape, but most likely, those components are under that white silicon.

[tibimakai]

Re: Onkyo SKW-591 subwoofer is dead

D922 was showing .76V same as D921.