Polk Audio PSW 110 subwoofer

[budm]

Re: Polk Audio PSW 110 subwoofer

I expect the - regulated power supply to be the same as the + regulated power supply.
https://www.badcaps.net/forum/attach...7&d=1529626412
I see two zener diode (red glass body with black stripe, one for each TIP Transistor, the Base pin of the TIP Transistor should be connected to the Zner diode. You need to check the DCV between the two legs of each Zener to see what you get, get the number as printed on the Zener will help also.

BTW, what are the P/N for those 3 ICs?
https://www.badcaps.net/forum/attach...9&d=1529536965

[R_J]

Re: Polk Audio PSW 110 subwoofer

I would find the 2 diodes that are off the secondary that feed the + & - supplies and check the voltage on the cathode of the positive supply and the anode of the negative supply.
The U2 TL084c does seem to recommend equal + & - supplies
U3 seems to be a LM324P

[budm]

Re: Polk Audio PSW 110 subwoofer

I would think those 3 IC will be quad op amp running on bi-polar power supplies, hope OP will get the P/N to verify the VCC pins.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

I will get the part numbers for U1, U2, and U3 and the other voltages you asked for when I get home from work.

The part number for U3 is visible in the picture. TL084C.

[budm]

Re: Polk Audio PSW 110 subwoofer

Check Voltages at VCC+, VCC- with ref. to circuit GND when the unit is working properly and when it is not working properly.

[R_J]

Re: Polk Audio PSW 110 subwoofer

I drew out the secondary component locations on the bottom of the board that might help, I believe it is correct

[frankusb]

Re: Polk Audio PSW 110 subwoofer

Nice, the second capacitor that I measured last night is between R78 and R81 I believe.

[R_J]

Re: Polk Audio PSW 110 subwoofer

I circled two blue capacitors, I believe C18 is one, its positve is connected to the other caps. negative, this point should be ground, or common. when you measure the voltage on C18 (-) it should be (-11) or same level as the (+) on the other cap. next to it. If its not I suspect eitherthe cap is bad, one of those resistors I marked changed value (went high).

[frankusb]

Re: Polk Audio PSW 110 subwoofer

Here is the data I collected, if I am missing anything, please let me know.

+ capacitor 13.15V
- capacitor -8.32V
+ zener diode cathode 11.7V
+ zener diode anode 0V
- zener diode cathode 0V
- zener diode anode -7.61

Zener diode 742A is what I can see without removal
U1 TL084C
U2 TL084C
U3 LM324DG

[budm]

Re: Polk Audio PSW 110 subwoofer

It looks to me that the (-) power supply feeding that - linear regulator circuit is too low.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

In circuit, the (-) capacitor measure 39uF (it's a 47uF), the (+) capacitor measures 48uF.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

Replacing the 47uF 63V capacitor pair resulted in a stable +/- 11V and proper operation. Now to decide if I should just replace the rest. Any advice?

[budm]

Re: Polk Audio PSW 110 subwoofer

Replacing the 47uF 63V capacitor pair resulted in a stable +/- 11V and proper operation. Now to decide if I should just replace the rest. Any advice?

Already suggested that in my post #4 which would have solved the problem by then and makes thread less than 33 posts.
Those caps get cooked in sealed cabinet without any ventilation.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

I agree with that assessment, my original post indicated that I thought recapping was a valid approach. Post #4 also suggested measuring the voltages and in hindsight I am very happy that I was convinced to take that route as I learned numerous approaches and methods that I think I will be able to use in the future. Thanks budm, Andrew and R J for all of your suggestions, ideas and input. I am very much more satisfied at having understood the problem versus a blind recapping.

The reason I asked about recapping at this point was that I was trading off the possibility that since I was unable to find specifications on all the capacitors, that there was risk in replacing them. Plus I could potentially damage the board in the rework. A wise person told me a long time ago to don't fix what's not broke.

[batch85]

Re: Polk Audio PSW 110 subwoofer

I'm servicing the same model, and unfortunately fatal power supply failure happened on my unit. And I need badly the identification of the burned components to be able to restore the unit effectively.I'm hoping Mr.franksub can tell me the exact components I need to know and replace. Q12(H28), the resisitors and maybe capacitors connected to it under the solder side of the board. And also the DC supply voltages on the secondary of the switching transformer that is the +VCC and maybe -VCC supplying the preamp section and the main output amplifier.Thank you sir franksub in advance for your time and effort.More power to you and God bless.

[Andrew F. Ali]

Re: Polk Audio PSW 110 subwoofer

I agree with that assessment, my original post indicated that I thought recapping was a valid approach. Post #4 also suggested measuring the voltages and in hindsight I am very happy that I was convinced to take that route as I learned numerous approaches and methods that I think I will be able to use in the future. Thanks budm, Andrew and R J for all of your suggestions, ideas and input. I am very much more satisfied at having understood the problem versus a blind recapping.

The reason I asked about recapping at this point was that I was trading off the possibility that since I was unable to find specifications on all the capacitors, that there was risk in replacing them. Plus I could potentially damage the board in the rework. A wise person told me a long time ago to don't fix what's not broke.

You are most welcomed, Sir. Glad you got this sub working again. You have learned what I did along time ago__When asking for help follow precisely the instructions given by the more learned ones and success will be had.
Regards.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

I'm servicing the same model, and unfortunately fatal power supply failure happened on my unit. And I need badly the identification of the burned components to be able to restore the unit effectively.I'm hoping Mr.franksub can tell me the exact components I need to know and replace. Q12(H28), the resisitors and maybe capacitors connected to it under the solder side of the board. And also the DC supply voltages on the secondary of the switching transformer that is the +VCC and maybe -VCC supplying the preamp section and the main output amplifier.Thank you sir franksub in advance for your time and effort.More power to you and God bless.

Sorry for the delay, I was out on business travel.

I cannot visually identify Q12. There seems to be a black film over portions of the part. I have taken some pictures but the don't look any better than visual inspection.

[batch85]

Re: Polk Audio PSW 110 subwoofer

Wow thanks a million for replying on my message,have you able to check or measure the correct supply voltages when you were able to restore your own unit. I wanted to know the supply voltages for the preamp and to the main output amp if possible.Thanks really for your time and effort.More power to you and God bless

[frankusb]

Re: Polk Audio PSW 110 subwoofer

Wow thanks a million for replying on my message,have you able to check or measure the correct supply voltages when you were able to restore your own unit. I wanted to know the supply voltages for the preamp and to the main output amp if possible.Thanks really for your time and effort.More power to you and God bless

If I understand your question correctly, the preamp supply voltage measured +/- 11V. I am not sure where to measure the main output amp supply voltages.

[budm]

Re: Polk Audio PSW 110 subwoofer

You need to look up the SPEC sheet of the SMPS IC, then you may find the application circuit that may give you some idea as to what the Q12 spec should be.
The filter cap for the power supply of the power amp section is marked in the picture, just look at the Voltage rating then you can estimate what the running Voltage for the power amp will be.
The Voltages for the pre-amp are already indicated in other posts.