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Who can repair a home audio circuit board? Polk powered sub died

wyliesdiesels

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Also 5+ year bump for a barely related new post.
yeah i was gonna reply to several comments on this then realized how old it was.

i have board level soldering repair experience and can do this repair but i doubt majority of people on here can. and the cost to pay someone to do it would outweigh the cost of a replacement
 
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dave*99

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yeah i was gonna reply to several comments on this then realized how old it was.

i have board level soldering repair experience and can do this repair but i doubt majority of people on here can. and the cost to pay someone to do it would outweigh the cost of a replacement
If anyone wants to burn, I mean learn, there are instructions on the internet. :oops:

1738877080522.png
 

Max

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Also the resistors burned due to another problem - they are victims and not the root cause of the problem.
 

dave*99

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Also the resistors burned due to another problem - they are victims and not the root cause of the problem.
Maybe not. They are likely voltage dropping resistors. They are in the power supply section. Since they are dissipating a couple watts they get hot. Discoloration of the board and resistors can happen.
They might not actually have failed.
 

Max

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Maybe not. They are likely voltage dropping resistors. They are in the power supply section. Since they are dissipating a couple watts they get hot. Discoloration of the board and resistors can happen.
They might not actually have failed.
You may be right. But it's also quite likely that something failed and caused a over current that then burned up the resistors.
 

Metal-Marc

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yeah i was gonna reply to several comments on this then realized how old it was.
This.

That's an easy fix, but as the saying goes: Damaged Beyond Economical Repair.

When people tell me if I want to fix their electronic ****, "it's an easy fix, just replace this resistor", I tell them how much I will charge for the repair, and they always change their mind.
 
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Since I have the same problem and decided to dig in to fixing my DSW500 subwoofer, I came across this garagejournal thread during my search, and as a registered member I figure I would chime in and help with what I discovered.


This is a thread that goes into detail on how to fix, with a schematic provided by Polk.


Here is the schematic without having to register on badcaps to download it.
 
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BurtEggley

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This is as someone indicated, an old thread from 2019 or so.

There was a crisis in the electrolytic capacitor market around 2000. Some guys in Korea stole the plans from a Japanese capacitor manufacturer, and made them for a lot less. The formula they took for the fluid was an old prototype without a special buffering agent in it so the caps swell up, release hydrogen and go ****, or spew corrosive fluid that damages boards. I would think most all of those have failed by now. In general capacitors are one of the first things to go in electronics. An old board from the 70's or earlier may not like being plugged in if they have shorted over time. (Hence the beginning of this thread and the burned resistors aka the magic smoke emitters.) :)

Since this thread was originally posted, we have noticed a couple businesses that fix old electronics and do pretty well at it, I think. I ran a regional repair center for Teledyne in the 1970's and spent many years in IT so these guys look good. The caveat is I have not used either, but would in a heartbeat. Do your own research on these folks. I am going off channel programs I have watched many times, and the level of equipment / knowledge and skill they have demonstrated. They have the equipment, dexterity, parts knowledge, model knowledge, and working history on the items they repair.

>Fixes Dell Laptops (I'd give him a 10 on 1-10) Part's People Austin Texas. He fixes Dell laptops at the board level (chips, resistors, caps, rebuilds burned traces, diodes, damaged connectors etc..)

>Fixes Big Screen TV's, especially Sony main boards and power supplies. He fixes other things too. (I'd give him a 10 on 1-10) Nick's Electronic Repair Tuscon AZ. He does boards for Ranges/Stove/Oven, Audio Equipment/Automotive/Commercial Vehicles/MAS & Servers/Game Consoles Retro Renegade Repairs, Televisions, even Bobcat loader consoles and electronics.

I don't know their hourly rate, but someone is not going to spend 3 hours fixing something for $75. I would guess they bill out the same as many tradespeople these days. Heck, we know a well known east coast dog handler that bills out at $200 an hour for show dog grooming. However, for the TV guy, a $350 - $300 repair plus shipping on a $1500 TV is not a bad deal. You have to pull the main board and send it, but they have guides on how to isolate which board to send and how to remove it etc.. Guy with the bobcat saved thousands fixing his old console vs buying a new one. The bobcat would not run when it failed. The Dell guy has saved many a laptop for a couple hundred dollars where a new main board might have cost a thousand dollars or more if really high end. You just send him the Dell laptop. He has done so many that he has donor boards and new boards that he can use to fix them. A laptop over 8 - 10 years old is not going to be worth fixing.
 
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PCustoms

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This is as someone indicated, an old thread from 2019 or so.

There was a crisis in the electrolytic capacitor market around 2000. Some guys in Korea stole the plans from a Japanese capacitor manufacturer, and made them for a lot less. The formula they took for the fluid was an old prototype without a special buffering agent in it so the caps swell up, release hydrogen and go ****, or spew corrosive fluid that damages boards. I would think most all of those have failed by now. In general capacitors are one of the first things to go in electronics. An old board from the 70's or earlier may not like being plugged in if they have shorted over time. (Hence the beginning of this thread and the burned resistors aka the magic smoke emitters.) :)

Since this thread was originally posted, we have noticed a couple businesses that fix old electronics and do pretty well at it, I think. I ran a regional repair center for Teledyne in the 1970's and spent many years in IT so these guys look good. The caveat is I have not used either, but would in a heartbeat. Do your own research on these folks. I am going off channel programs I have watched many times, and the level of equipment / knowledge and skill they have demonstrated. They have the equipment, dexterity, parts knowledge, model knowledge, and working history on the items they repair.

>Fixes Dell Laptops (I'd give him a 10 on 1-10) Part's People Austin Texas. He fixes Dell laptops at the board level (chips, resistors, caps, rebuilds burned traces, diodes, damaged connectors etc..)

>Fixes Big Screen TV's, especially Sony main boards and power supplies. He fixes other things too. (I'd give him a 10 on 1-10) Nick's TV Repair Tuscon AZ. He does boards for Ranges/Stove/Oven, Audio Equipment/Automotive/Commercial Vehicles/MAS & Servers/Game Consoles Retro Renegade Repairs, Televisions, even Bobcat loader consoles and electronics.

I don't know their hourly rate, but someone is not going to spend 3 hours fixing something for $75. I would guess they bill out the same as many tradespeople these days. Heck, we know a well known east coast dog handler that bills out at $200 an hour for show dog grooming. However, for the TV guy, a $350 - $300 repair plus shipping on a $1500 TV is not a bad deal. You have to pull the main board and send it, but they have guides on how to isolate which board to send and how to remove it etc.. Guy with the bobcat saved thousands fixing his old console vs buying a new one. The bobcat would not run when it failed. The Dell guy has saved many a laptop for a couple hundred dollars where a new main board might have cost a thousand dollars or more if really high end. You just send him the Dell laptop. He has done so many that he has donor boards and new boards that he can use to fix them. A laptop over 8 - 10 years old is not going to be worth fixing.


Well ok then...
 

BurtEggley

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Well ok then...
the OP asked who could repair his Polk circuitboard with burned out components. The Polk unit was probably not worth repairing but since he asked, Nick's could do the work if someone else finds this thread and has the same kind of question.
 

PCustoms

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the OP asked who could repair his Polk circuitboard with burned out components. The Polk unit was probably not worth repairing but since he asked, Nick's could do the work if someone else finds this thread and has the same kind of question.

As you yourself noted this is a 7yr old thread...

No clue who/what Nick's is, I think you may have forgotten something in that long post
 

knobby

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Just my 2 cents but powered sub amps have the most common failure rate of any home audio and i suspect that this has something to do with insufficient isolation of the signal from the amp circuitry.
With the receiver or source on one household circuit and the amp on another there is potential for for a loop that over time will cause issues.
The point that i am trying to make is that it is a good idea to make sure that your main amplifier,any signal processing and the powered sub are all powered from the same circuit.
 

dave*99

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With the receiver or source on one household circuit and the amp on another there is potential for for a loop that over time will cause issues.
The point that i am trying to make is that it is a good idea to make sure that your main amplifier,any signal processing and the powered sub are all powered from the same circuit.
Crossing multiple circuits on an audio system can give you a hum from a ground loop. But that won’t damage a plate amp in a subwoofer.
There are lots of quality issues in those amps from the start.
 
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