Help identifying electronic components

[GMJim]

Hello all!  First post here out of desperation.  I'm hoping someone can help me identify these three electronic components on a circuit board for my Polk DWS Pro 500 sub woofer. They want a bunch of money to replace the entire panel with four printed circuit boards on it. If I can identify the component with P6? printed on it I may be able to solder a new one in and repair this myself. I think the IC chip is toast too as one pin is burnt off.  I'm quite willing and capable to solder in new components but I must admit I'm a noobie with this stuff.  Any suggestions are greatly appreciated.

I wanted to post this in Chit Chat but it wound up here?
Thanks

 

[HarryA1]

The eight leaded DIP is a " Low power offline switched-mode power supply primary switcher" see:

file:///C:/Users/harry/AppData/Local/Temp/viper12a-e.pdf

The larger diode P6? maybe a protection diode to protect from over-voltage. The  two smaller diodes most likely  are rectifiers used as part of the power supply. The question is what caused the fault that damaged the components.

You need to investigate that before replacing the components else they may just blowout again.

Try drawing out that part of the circuit to get insight into the circuit.

 

[GMJim]

HarryA

Thank you very much for the reply and advice.  While investigating this I found at least three other posts on various audio websites showing exactly the same failure and dates on the board indicate approximately the same production dates.  I can only assume this is a weak point in design.  Polk Audio won't repair the board and won't replace just this board on the panel but wants to sell me an entire panel with all new boards obviously at a cost.  I've owned this speaker for 22 years and it worked well so I figure if I replace the burnt components I might get lucky.  I'm a retired auto technician so handy with a soldering gun but NOT knowledgeable in electronics repair.  After looking for an electronics repair shop and coming up empty I decided to try fixing it myself with $5.00 worth of parts instead of a few hundred dollars for a new panel.  I'm going to call Polk audio Monday to get more information.

Thanks again for the help!

 

[HarryA1]

Yes, you are not the only one with that problem! See the circuit here:

https://www.ebay.com/itm/Polk-Audio-DSW-PRO-500-Subwoofer-Amp-Plate-Not-Working-For-Parts-Repair/184441091699?hash=item2af18bb673:g:2~QAAOSwEkxfWY2A

I was thinking you could get the correct parts from that one but no such good luck.

 

[Guy Shemesh]

Hello Jim,

I think the fix would be fairly easy, assuming that P6 is the only diode that got burned. If the failure propagated elsewhere in the circuit there might be more damage but my gut feeling says you have a really good chances here. 

Looking at the Viper IC I see it is self protected, Overtemperature, overcurrent and overvoltage protection - so I wouldn't bother to replace it. You just need to pick a diode at a rating similar or high to the P6 diode. If you have the exact P/N that would be the best, otherwise just pick a diode with slightly bigger dimensions. 

Now the trick is a follows. You don't want to get into the over temperature problem again. This is a design flaw of this circuit and part of the fix would be to avoid it as well. So what to do? Apparently you could help to cool the replaced P6 diode just by leaving its wire leads uncut on both sides long. When you install the new P6 diode, don't cut the wires on both sides. Take care that these leads wont touch anything unintentionally in the circuit, you could also bend them in directions to ensure this. Moreover, you could even extend these leads or just add solder to the excessive leads, this really helps to cool them since more mass - more surface area - better heat transfer to ambient.

I had a similar issue with a customer who brought in a really expensive microphone's power supply. It was not our design but we promised to look at it anyway and bang - same issue - diodes heating up and burning the circuit. 

If anything unclear you could also post pictures here after the fix and before powering the unit.

Good luck

Guy

 

[GMJim]

Guy

Thanks for the encouraging information.  After searching several places on the internet I found several examples of the same board with exactly the same issue.  Since reading that there may be reason for this upstream I looked closer at other components and found two components with a black substance melted?? and settling at their base.  I'm not sure if it's a goop applied for vibration issues or the component melted down.  The IC switch also has a pin burned off that I mentioned this in the previous post.  I'm attaching a few more better pictures.  If you feel I can save the board I'll take a shot at it but I'm having a difficult time finding a diode.

 

[Guy Shemesh]

Oh! 

I'm sorry to see this, looks like there is further damage. The caps are severely damaged.. 

No I would not recommend to try and save this board. 

I would let it go

 

[HarryA1]

If you compare your  board with the one on Ebay that one looks like the better board.

You may gain some insight by comparing the P6? on your board with the three in the schematic and see if it connects the same as one of them. This is the schematic of the Viber12a in a battery charger.

 

[GMJim]

Thank you everyone for your help and advice.  I found a brand new updated AMP plate (DSW Pro 550) for $150.00.  I think I might just keep this one (DSW Pro 500) for parts.

Thanks again!

 

[Guy Shemesh]

That would be the best! Good luck