Polk Audio PSW 110 subwoofer

[frankusb]

Hi,

My brother in law got a sub-woofer out of the trash for me. It's a Polk Audio PSW110. It works but seems to go in to a kind of protect mode at higher volumes and lowers the output considerably for a period of time and then starts playing again. To me that feels like a capacitor in the power supply may be giving out. The attached pictures, to my eye, do not look visibly failed.

Does anyone have a schematic? Short of that I am inclined to recap it (at least the polarized capacitors).

[budm]

Re: Polk Audio PSW 110 subwoofer

https://www.badcaps.net/forum/attach...2&d=1529196489
Did you remove the clamping bar that holds those TO-220 device tightly against the heatsink?

[frankusb]

Re: Polk Audio PSW 110 subwoofer

I removed 3 clamping bars so that I could take a picture of the bottom of the board.

[budm]

Re: Polk Audio PSW 110 subwoofer

So it has power supply/power amplifier combo board, the other board is the preamp/input board. There are 5-pin connector that goes to the preamp board, you can test and record the Voltage of all 5 pins before and after it acts up.

There are lots of threads about this 110 sub. You may try recapping it at this point.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

Anyone have any datasheets on PVAN or MHC capacitors? I found the JUNZL PL series datasheet and the SK series datasheet.

There are 8 polarized capacitors.

PVAN CD268 400V 150uF
JUNZL SK 35V 100uF
MHC CD263 63V 10uF
JUNZL PL 63V 120uF
PVAN CD268 63V 47uF
PVAN CD268 63V 47uF
JUNZL SK 50V 47uF
JUNZL SK 50V 47uF

[frankusb]

Re: Polk Audio PSW 110 subwoofer

So far I've found that this is a BASH amp (did not know those existed, nice reading) which is either designed all or in part by Sonavox. The PSW 111 contains the same amplifier board apparently.

I've got a set of capacitors in my basked on Mouser but I have not pulled the trigger yet.

[Andrew F. Ali]

Re: Polk Audio PSW 110 subwoofer

So it has power supply/power amplifier combo board, the other board is the preamp/input board. There are 5-pin connector that goes to the preamp board, you can test and record the Voltage of all 5 pins before and after it acts up.

There are lots of threads about this 110 sub. You may try recapping it at this point.

Did you follow this advice? If you did what were your findings??

[frankusb]

Re: Polk Audio PSW 110 subwoofer

I have not measured the voltage of the 5 pins. I'm only using the LFE input, I can't believe it would be related to the issue.

I have not recapped yet, I will probably order from Mouser today. I've been studying the circuit and thinking on it.

[Andrew F. Ali]

Re: Polk Audio PSW 110 subwoofer

cool

[budm]

Re: Polk Audio PSW 110 subwoofer

Voltage measurement is one of the first thing you do beside visual inspection when troubleshooting, bad Voltage = problem.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

Maybe I mistakenly assumed, but I figured I would only see audio signals on the connector, no rails.

[budm]

Re: Polk Audio PSW 110 subwoofer

I have not measured the voltage of the 5 pins. I'm only using the LFE input, I can't believe it would be related to the issue.

I have not recapped yet, I will probably order from Mouser today. I've been studying the circuit and thinking on it.

The sub woofer needs active circuits to process the incoming audio, hat board has OP-amps for the preamp and low bandpass amplifiers which requires bi-polar power supplies to run plus detection/timer circuits for auto ON/OFF function, usually +/- 12 ~18VDC.

It has 5 wires so they should be GND, +VCC, -VCC, Audio, and Control for Standby on/off; that will be typical setup.
I already gave you the suggestion as to what to test at least, it is up to you to follow the suggestion or not, I am out since I have better thing to do.

[Andrew F. Ali]

Re: Polk Audio PSW 110 subwoofer

Part of original post by budm:
It has 5 wires so they should be GND, +VCC, -VCC, Audio, and Control for Standby on/off; that will be typical setup.
I already gave you the suggestion as to what to test at least, it is up to you to follow the suggestion or not, I am out since I have better thing to do.

Agreed 1000%

[frankusb]

Re: Polk Audio PSW 110 subwoofer

My mistake, thank you for the explanation. I will check.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

I was so wrong....

[frankusb]

Re: Polk Audio PSW 110 subwoofer

All right, RCA input jack ground appears to be on brown and several other points (knob shell for volume/crossover). Relative to ground:

On mode, no audio
Yellow -6.14
Orange -0.008
Red -6.7
Brown 0
Black 11.03

Playing
Yellow -7.5 - -8 varied
Orange -0.00ish
Red -8 - -11
Brown 0
Black 11.03

Broke mode (mostly plays at reduced volume but some bass hits hard for maybe 1/2 second every 6 seconds)
Yellow -8.5
Orange -0.00ish
Red -8ish
Brown 0
Black 11.11

Standby
Yellow 1.36
Orange -0.055
Red -7.00
Brown 0
Black 11.00

[R_J]

Re: Polk Audio PSW 110 subwoofer

That Red -7 volts seems low, most amps usually have plus and minus voltages that are close to the same voltage, I would expect around -11 volts. If you have not replace the cap on the negative side it could be bad, I also see two components on seperate heat sinks (H18 & H19) are those regulator ic's or just transistors? and are they connected to the + - pins.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

The output of Q22 (HI8) is connected to Red and has a 47uF 50V capacitor in parallel. In circuit measurement of the capacitor is 73uF. The output of Q7 (HI9) is connected to Black and has a 47uF 50V capacitor in parallel. In circuit measurement of the capacitor is 66uF. Measurements done with a Fluke 12.

It's hard to read the numbers without removing the components but I've got a partial number in the attached pictures, TIP3??? BJTs?

[budm]

Re: Polk Audio PSW 110 subwoofer

Check the DCV between each heatsink of the TIP3x transistor against GND to see what you get. Do the same on the Emitter pin of each TIP3x against GND.

[frankusb]

Re: Polk Audio PSW 110 subwoofer

Q22 heatsink measures -8.6, Q7 heatsink measures 13.2.

Based on https://cdn.badcaps-static.com/pdfs/...4a008e39e0.pdf, the emitters were what I measured on the 5 pin connector, no?