Looking for 550WI schematic

DaVinci856

(I incorrectly first posted this in the wrong forum area, so copying it here. I'll be doing a little circuit checking today in any case, so possibly I'll find something helpful before I see a response, but any help would be welcome.)_

Hi All.
My DSW PRO 550WI runs for almost a minute and then the power dies. (All the lights go out.) I pulled the power supply board and started looking at it and found that things get past the bridge, but that everything at the output connectors goes dead when things go south. I'll be checking the control signals and such, but it would speed things up a lot if I had an actual schematic. I'm looking up some component data sheets and actually started drawing a rough schematic myself, but this could be quite time consuming. Unpowered circuit tests of the semiconductors have not been revealing so far, but that was just a way to get a quick start before making extensions for the interface plugs. If anyone could provide a drawing, it would be really appreciated.
Thanks.

SeleniumFalcon

I'll ask a friend at Polk for you.

DaVinci856

Thanks! I started looking at this, btw, and am creating a schematic (which is very slow). I also started some general troubleshooting and saw that CN3 and CN4 pretty much all drop to zero when it fails, but it only failed two short times and came back about 10 seconds later each time. (Makes me wonder about cold solder, but haven't seen any evidence of that yet.) The voltages either follow the numbers printed on the board or appear reasonable under normal conditions. If I could get it to fail again, it would really help, but this one is intermittent, which makes it ever so much more "fun". I was originally thinking that possibly a problem in another board was sending a control to shut things down, but not enough info to believe that yet. I have an errand first, but will get back to this a little later today. Thanks again.

DaVinci856

Well, I got back to my project and MIGHT have found an issue, but I'm not convinced. I may have found a cold solder on the board, but I'm not really sure, because it didn't look too bad even under a magnifier. In any case, I resoldered it and the sub ran for about 45 minutes with no issues. I did remove a few electrolytics and saw they'd dried out a bit and lost about 10-15% over time, so may just replace them to avoid other issues. Their ESR was well within spec, but the 2200uFs (C5+C6), for example, dropping to just under 1000 is enough to make me want to do replace them, so I'll do some preventative maintenance in any case. I will put the sub back into service and wait for it to fail. We'll see. I'm suspecting this isn't done. I'd still appreciate the schematic if it can be obtained, because, for example, taking out T2 just to find out which terminals did what, was annoying. Thanks.

DaVinci856

Yeah, typo there...C5/C6 to just under 2000...

SeleniumFalcon

I have sent an email.

DaVinci856

Thanks. I've got several caps on the power supply on the edge (by capacity and ESR), so have ordered some high quality electrolytics to replace them in any case. Also replacing TVS1. Doesn't SEEM to be bad, but was throwing off a lot of heat, to the point where it badly discolored the board and I question whether it's reliable. It's a simple, inexpensive replacement while I'm in there, anyway. As it was the unit was running for about an hour and then fail for a minute and come back, so I'll see if that affects anything. In my haste I didn't order replacements for a couple on the amp board, but that may happen in the future.

DaVinci856

Well, it looks like I MIGHT have fixed the sub. I found a couple of bad caps, and after replacing those, it appears to be stable. I'm still going to work on the schematic a little more just in case, however. If a real schematic does show up, it would save time, but if I get this a little more done, I'll post it in case anyone else needs it (with the obligatory, disclaimer about errors). It's really annoying that companies often consider these confidential, but such is life.

DaVinci856

Well, it's been about a week, and all seems good. Just in case this might help others, in my case, C17 looks like it was the culprit. It's part of the standby 5v supply and had a very high ESR (measured 2.6 ohms in circuit when it should be about 0.6). When I removed the cap, it was about half the capacitance it should have been as well. Interestingly, the ESR jumped to 44 ohms out of circuit, which was puzzling, but also way beyond normal of course. That variability might also explain the intermittent failure, though.
While I was there, I also replaced C8 and C20, which also had ESR values that were a little higher than I thought they should have been, even though their capacitance measured OK after I removed them. I kept the extra ones I ordered just to have on hand, but it appears that my issue is resolved.

zcarello

I realize this is a few months late, but did you ever receive a schematic? I have a dsw 660 that died. The capacitor at c14 went and fried the leg of the inductor at b1. Unfortunately I can not identify any markings on the b1 inductor so sourcing the correct replacement has proven difficult to say the least.

MizztaPeppa

I am also having board issues with my 660, any look on that schematic? Thank you

SeleniumFalcon

Schematic sent...

mgh333

Any chance I could get a look at that schematic? I have a 550 thats been powering off after 10-20 seconds. But when I pulled it apart and started to trouble shoot it started working again. ugh. Pretty sure it's the power supply since the 46v rails slowly got down when it stops working. But I was just to the point of measuring the amps power protect line to make sure it wasn't shutting down the PS when it started working again. So I know it's just a matter of time before it fails again. Thanks.

SeleniumFalcon

Schematic sent...

Shinji

Hi,
looks like another 550WI problem, Green light is up on back but no blue led on front, no sound T_T
Love this product, Did an attemps to repair,
So looking too for 550WI schematic, please
Thanks in advance, Best Regards.

SeleniumFalcon

Hello,
Sent to you.
Cheers!

Shinji

Hi,
Yeah Great

I didn't expect you to be so fast ^^'
I thank you very much for your responsiveness.

SeleniumFalcon

You're welcome, good luck with the repair!

Shinji

I took the rear panels off today.

Everything seems clean on the capacitor side, nothing seems to have exploded or leaked onto the card.
(on the other hand there is a sort of glue everywhere, probably for transport and against shocks, but that does not simplify the task).

By checking more closely there is a resistor (R8) which has a little green on the solder pad, and by scratching a little it has completely unsoldered from the card, therefore potentially defective,
82K Omhs, small order made, I didn't have any in reserve.

I'm not touching the rest too much for the moment, the large power capacitors can stay charged for a long time, within 2/3 days it will be ok.

SeleniumFalcon

There is some evidence that it is possible, over time, that the glue can be come conductive as it ages. It was used to hold components in place during assembly. You can discharge capacitors by placing a 10k ohm resistor across the terminals for a few seconds. There are discharge tools available also.

Shinji

Back,
a little better since the replacement of the R8 resistor, the blue LED on the front now lights up.
But still no sound comes out T_T

pitdogg2

Time to buy a new sub. Most Polk subs were never long lasting and mostly terrible.

F1nut

^BINGO^

Shinji

Another investigation, but nothing found.
I replace the Card on the back panel and remount it together with sub.
let try another time with power supply ...

Turn On ... and .....
Hummm big Clack, and hummm smell component smoke (very particular isn't it XD)

THX203H-7V completly exploded ....

Should I try another component replacement (THX203H-7V is not expensive at all) .... but is it him or another root cause T_T