PSW150 Problems...schematic available?

MuseChaser

Before I detail the issues with a new-to-me PSW150 powered sub, know that I did call Polk customer support yesterday to request a schematic. The first person I talked to told me "they don't carry that product....wait, do you mean the thing that tells you how to install it?" Seriously. I laughed out loud..couldn't help it. I asked nicely if I could talk to someone with some technical knowledge of their products and was connected to another representative. She seemed to know what a schematic was, but informed me they didn't have one. I find that very hard to believe, and I'm hoping she was mistaken.

Can any Polk representative or third party please help by providing a schematic? I'd be happy to purchase one, or a service manual containing the schematic.

Now, the issues. Power indicator glows red, internal relay can be heard switching on, but no sound except for a loud pop/crack when turning off power. Phase toggle switch inoperative and frozen in place.

Discoveries upon disassembly so far...

1. No continuity between any contacts of phase switch. I removed the switch from the control board and found a replacement switch to be ordered.

2. Strange insulated jumper wire soldered to bottom of control boards between diods and a pin of one of fhe ICs. Is that factory?!?

3. Jumper wire W19 has been removed, although there is evidence of remnants of it remaining in the mounting holes. The under-board jumoer wire does NOT duplicate the connection of W19.

4. The red power led was connected by having its bare leads shoved into a jst connector, then just globbed up with silicone. Is that factory, too?

5. Poor thermal paste coverage on at least two of the heat sink mounted transistors.

6. Dried brown goo underneath the large 10,00p mfd 50v caps, and on some of the smaller green caps. Some electrolytics show visible corrosion on top, but measure within capacitance tolerance. I don't have anything that will measure ESR.

7. Lots of gobs of silicon holding various caps and resistors in place. Factory, or someone else's work?

8. Internal fuse is fine.

Thanks for any assistance. Would love to hear from a Polk representative.

SeleniumFalcon

I'll ask a friend at Polk for the schematic.

MuseChaser

Thank you, SF... much appreciated.

MuseChaser

Just a quick bump for this... still hoping to hear back from Polk personnel ..

Can anyone confirm or deny that wire jumper W19 is supposed to be in place (it's been clipped off on my control board) and that an insulated white wire connecting the node between (diodes D108, D109, and one leg of the missing W19) and the non-inverting input (pin 3) of IC102, a JRC4558, on the underside of the control board is a factory addition, and not the work of some other attempted repair?

Here's a pic of the bottom of the control board I annotated ...






I would LOVE to get my hands on a schematic... PLEASE...

MuseChaser

Here's an annotated pic of the top of the control board ....

MuseChaser

Just some further observations as I compile a component list...

On this board, there are two different C114s, and two different C119s. There's also an unpopulated resistor spot underneath one of the pots (that's not all that unusual) and a resistor with no label etched on the board on one edge of the board.

SeleniumFalcon

One of Polk's engineers may have found it, I'll send it to you when possible.

SeleniumFalcon

I've sent it to you via email.

MuseChaser

Thanks very much, SF! I'll look for it.. nothing yet.

As an aside for anyone else reading, I called Polk again this morning, but couldn't get anywhere.. the rep was pretty steadfast that they couldn't or wouldn't provide a schematic. Sooooo...,.

I stared at the circuit a bunch, and the more I though about how the added wire routed a signal meant for the 6080D D+ input to the non-inverting input of one of the 4558 chips, the less sense that made. Same with the removal of W19, which PREVENTED the signal from getting to the 6080 D+ input. All I can figure is that, when the phase switch went defective, someone with really poor eyesight attempted some really bad way of bypassing it... who knows.

Throwing caution to the wind, I replaced W19, removed the added under-board insulated jumper wire, and bridged the center and 0deg tabs as a means of bypassing the faulty phase switch I removed.

Bound the speaker leads to a dummy load and powered it up. Red indicator light, no magic smoke left... so far so good.

Hooked up the scope, fed some test signals... Hmmm... traces look good, frequencies are correct, a little bit of oscillation up around 150K, but otherwise nothing remarkable. Low pass adjustment and volume adjustments work. Sooo..

Tried music input instead of test tones. Traces as expected... Sooooo....

Hooked it up to a cheap speaker, just in case, and tried it at low level...

Works! I need to reapply some damping silicone or hot glue before placing it in the original cabinet with the driver, but I think we're out of the woods.. at least for now. I will check things over when I see the schematic.... thanks again, SF!!!!

SeleniumFalcon

I re-sent the schematic.

MuseChaser

Got it. You're the best.. thank you VERY much!!! I just tested the amp with the drive in the enclosure... works great... except the driver buzzes and rattles like crazy at anything other than very quiet excursions. Pulled it.. the corrugated spider had separated from the frame. Just reglued it... should be good to go tomorrow. Very excited... can't thank you enough for the help.

SeleniumFalcon

Well done, I'm glad you've got it working properly. Cheers!