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Old 04-26-2019, 10:51 AM   #1
tibimakai
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Default Onkyo SKW-591 subwoofer is dead

Somebody gave me the whole system for free. Receiver's HDMI IC is getting extremely hot, course, there is no HDMI in/output and this sub is dead.
HDMI IC was replaced already by previous owner.
But this thread, is about the subwoofer.
I have found the final dual FET transistor Q502, shorted across +/- power supply(pin 1 & 5) and Q952 FET, at the power supply shorted as well.
I have just replaced them, but at the speaker output, I'm measuring over -7V DC. Q951/Q952 are starting to heat up really fast.
D515 and D516 are good.
There is not much time to start measuring.
What should I start measuring?
Any help would be appreciated.
Here it is the SM:
elektrotanya.com/onkyo_htp-591_skw-591_sm.pdf/download.html

Read more: http://repairalmostanything.com/thre...#ixzz5mDm0XNkL
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Old 04-26-2019, 10:52 AM   #2
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Default Re: Onkyo SKW-591 subwoofer is dead

I have went over all the components, at the final amp section and I have found, three 33 Ohm resistors that were bad(high value). R505, R511 and R513 are the blown values.
Unfortunately, after I have replaced these resistors and I have turned it on, heard a whistle like sound and than a slight pop-pop-pop sound and I knew that Q502 was shorted again.
And it was. I have only seconds, until it blows.
The voltage, at the speaker output it was still -7.xxV.
How should I proceed repairing this amp?
I still have another final amp IC.
I shouldn't solder it in, and try the power supplies first, if they have the proper voltages?

Last edited by tibimakai; 04-26-2019 at 11:40 AM..
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Old 04-26-2019, 11:21 AM   #3
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Default Re: Onkyo SKW-591 subwoofer is dead

If R511 & R513 were damage It is very likely Q501 IC is bad, If R505 was open I would suspect C501 could be damaged also.
You might be able to work on it without Q502 installed I would also check the value of all the resistors/diodes in the output circuit. If one of the resistors is open it can effect the offset voltage and blow the output
Check R528, it should supply +12 volts to the ic

Last edited by R_J; 04-26-2019 at 11:41 AM..
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Old 04-26-2019, 11:39 AM   #4
tibimakai
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Default Re: Onkyo SKW-591 subwoofer is dead

I will place an order for a new IC & capacitor, and I will check that capacitor, but if I remember correctly, it wasn't shorted.
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Old 04-26-2019, 11:59 AM   #5
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Default Re: Onkyo SKW-591 subwoofer is dead

there was enough current flowing through c501 to open R505, download the pdf for the irs2092, it has internal fets and you should be able to check them and give some idea of what is going on. IE: if fet across VB & HO is shorted etc.
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Old 04-27-2019, 11:56 PM   #6
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Default Re: Onkyo SKW-591 subwoofer is dead

At pin #12, where it should be 12V, I measured -39V(!). GND I took it, from pin #2.
I have removed Q901(7812 regulator) and -40V it was still there.
I have went through all the parts in the amp section and only the three 33 Ohm resistors were bad, which I have replaced already.
Just for good measure, I have replaced the 470uF capacitor. It was showing 4.3 Ohm ESR.
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Old 04-28-2019, 12:17 PM   #7
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Default Re: Onkyo SKW-591 subwoofer is dead

I looked at the schematic again and the +12 VB volt uses -39 volt supply as ground, to check the 12 volts use COM (Pin10) on the ic or measure across C503
The amp ic is used in bi-amp mode, It uses the -39v supply for the 12 volt regulator's ground, not chassis ground
Were you able to check the ic's internal fets to see if any are shorted?

Last edited by R_J; 04-28-2019 at 12:30 PM..
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Old 04-28-2019, 06:05 PM   #8
tibimakai
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Default Re: Onkyo SKW-591 subwoofer is dead

There is 0V with 7812 installed and IC removed.
It seems like, between pin #15 and 14 there is a short, and between 12 and 11, there is another short. So the upper FETs, at both channels.

Last edited by tibimakai; 04-28-2019 at 06:34 PM..
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Old 04-28-2019, 07:26 PM   #9
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Default Re: Onkyo SKW-591 subwoofer is dead

I would check for around +15 volts across C905, it needs to be there before you will have the +12 volts from the regulator, Q902 needs to be turned on by Q903.
The IRS2092's VCC is turned on and off by that circuit

Last edited by R_J; 04-28-2019 at 07:29 PM..
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Old 04-29-2019, 06:51 PM   #10
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Default Re: Onkyo SKW-591 subwoofer is dead

Across C905, I measure 26V.
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Old 04-29-2019, 08:39 PM   #11
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Default Re: Onkyo SKW-591 subwoofer is dead

Thats likely what it should be, When the sub turns on Q902 supplies Q901 regulator and that 12 volt regulator is what supplies the vcc voltage to turn on the amp ic
Earlier when you replaced the resistors and Q502 had you also replaced the Q501 ic or only the resistors and q502?

Last edited by R_J; 04-29-2019 at 08:45 PM..
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Old 04-29-2019, 08:59 PM   #12
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Default Re: Onkyo SKW-591 subwoofer is dead

Only the Q502 and resistor. I did not know that Q501 was bad.
I need to order some.
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Old 05-05-2019, 10:40 PM   #13
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Default Re: Onkyo SKW-591 subwoofer is dead

I have replaced both ICs in the amp section, and there is still an issue.
DC voltage is 2.3V.
I have noticed that the schematic on elektrotanya, is not the right one.
There are no 7805 or 7905 ICs, on the board. There is only a 7812. 12V is there.
It seems like the amp +/- voltages seem a bit off. One side is like 2V higher than the other and slowly increases. The DC voltage at the speaker output is slowly increases as well.
I have measured all the components in the amp section, and they all look OK.
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Old 05-06-2019, 07:03 PM   #14
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Default Re: Onkyo SKW-591 subwoofer is dead

Quote:
DC voltage is 2.3V.
where? across the speaker? what is in place of the regulators? anything? is Q433(C) connected to VAA
I can't see +/- being off a couple volts being an issue unless the filters C901/902 are bad. Also are the ic's getting hot? Make sure R525 is ok as it takes the offset voltage and feeds it back to the input for compensation.
If the schematic is not the same I'm not sure how I can help.
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Old 05-06-2019, 07:06 PM   #15
tibimakai
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Default Re: Onkyo SKW-591 subwoofer is dead

Across the speakers.
Everything installed, except the speaker.
The final IC is not getting hot, I haven't checked Q501.
R525 is OK.

Last edited by tibimakai; 05-06-2019 at 07:11 PM..
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Old 05-06-2019, 07:16 PM   #16
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Default Re: Onkyo SKW-591 subwoofer is dead

I would see what the voltage is with the speaker connected and if you have any hum. It could be that the 2.3v is due to the lack of a load
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Old 05-06-2019, 07:18 PM   #17
tibimakai
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Default Re: Onkyo SKW-591 subwoofer is dead

It has a loud brrrrr.
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Old 05-06-2019, 07:44 PM   #18
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Default Re: Onkyo SKW-591 subwoofer is dead

If this sub used a regular 60hz power supply that would sounds like a bad main filter cap, but this uses a switching power supply so that should'nt sound like that if the caps were bad

This sub does use the switching power supply correct? (q951/952,Q953) or is that part also different?

Last edited by R_J; 05-06-2019 at 07:57 PM..
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Old 05-07-2019, 09:01 AM   #19
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Default Re: Onkyo SKW-591 subwoofer is dead

I know for sure that Q951/952 is there, because one of them it was shorted and I have replaced it. Most likely, Q953 is there as well. I will check it, when I get home.
The +/-40V and 12V is there.
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Old 05-08-2019, 11:11 PM   #20
tibimakai
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Default Re: Onkyo SKW-591 subwoofer is dead

I have tried with the speaker. It just pops ones as I plug it in, the cone extended and stays there.
The brrrr, seems like it's gone.
The first time did not make anything, I had to touch the input and that started the popping as a I plugged it in and the cone extended.
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