Amp repair questions

[jmanpc 5,000+ posts]

Okay, so if you didn't see my other thread, here's a brief synopsis. My amp is slowly dying- when I crank up the volume above~65%, the speakers all fade out and turn to muddled garbage till I get off the volume. The amp stays on, no protect light or anything. My best guess, and the consensus seems to be that my power supply capacitors are failing.

Since the amp was $135 brand new, and repairs would probably cost $100, there is no sense in getting it repaired by a repair company. Instead, I think I'll spend $20 and just repair it myself. If that doesn't work, I can just get a new one.

After cracking it open and inspecting the guts, I have found that the power supply has twelve capacitors- 8 2200uf, 50v capacitors and 4 2200uf, 35v capacitors.

My first question is, what is the difference in different capacitors. While searching, I stumbled upon these and these. Obviously, the capacitors on PartsExpress are a name-brand and a bit more expensive. The others are generic and cheap. Is it worth it to spend the extra money, or is a capacitor a capacitor. I assume it'd be better to spend the money to get higher quality parts.

Secondly, what is the process by which you solder the parts on? I assume from my previous soldering experience that it's as easy as heating up the solder to remove the old caps, and then putting the new ones in and just putting a new bead of solder on. Any tips or tricks?

Any advice would be appreciated. Thanks in advance for your help.

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[big bass joel 10+ year member]

pm chris at dbr electronics?

 

[big bass joel 10+ year member]

or pm makeshift out of oklahoma?

 

[jmanpc 5,000+ posts]

Why would they want to tell me how to fix an amp when thats how they make a living? If they want to chime into this thread, I'd be appreciative, but I don't expect them to chip away at their own profits.

 

[l7runner 10+ year member]

It will be easy to pull out the old parts. Just pull the board from the heatsink flip it over and heat up the solder joint from the back. With the solder molten you can easily remove the part by pulling it out. Replace then resolder the connection.

How have you came to the conclusion that the caps are bad? Be sure to check all mosfets/transistors for shorts, you may even want to check out the voltage on the pins of the pwm chip.

good luck

 

[bubbagumper6 5,000+ posts]

I would buy from here: DigiKey Corp. | Electronic Components Distributor | United States Home Page

You have the part number from the stock caps?

 

[jmanpc 5,000+ posts]

I'd have to crack it open and look again.

 

[bubbagumper6 5,000+ posts]

I'd have to crack it open and look again.

Well your going to want to replace them with something as close as possible to the original. You don't want to just throw any old caps in there. So open it up, write down the factory part number, and look it up on digikey.

 

[jmanpc 5,000+ posts]

Thanks for that site. Looks like they've got everything you'd ever need //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[bubbagumper6 5,000+ posts]

Yeah they do, we use them at work all the time, if they don't have what your looking for, or you want another price quote, try Mouser Electronics - Electronic Component Distributor

 

[Grinder1989 5,000+ posts]

Best guess? So change parts and see if it works? Bad idea. Waste of time and money. Get it checked out by someone who knows how to repair an amp before you attempt to do it yourself.

 

[jmanpc 5,000+ posts]

Best guess? So change parts and see if it works? Bad idea. Waste of time and money. Get it checked out by someone who knows how to repair an amp before you attempt to do it yourself.

See original post. Why would I pay someone to fix it when I could buy a brand new amp for $30 more? I just see an opportunity for experimentation. If I smoke this amp, then it won't be a big deal.

 

[Haunz 10+ year member]

Just pull the board from the heatsink flip it over and heat up the solder joint from the back. With the solder molten you can easily remove the part by pulling it out. Replace then resolder the connection.

He should be using a solder-sucker to get all old solder out of the mounting holes before trying to pull the caps out...

With that said, failing caps are often pretty obvious because they swell up and even burst... if you still think it's bad caps try pulling one out and check it with a DMM.. (many will measure capacitance)

I too would recommend getting the amp benched at a repair shop... many will give free estimates, so it won't necassarilly cost you anything to have a professional look at it...

 

[jmanpc 5,000+ posts]

Problem is, I live in nowhere, Arkansas, therefore, I don't have an amp repair shop in the neighborhood //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[Johnny Law.Lulz 5,000+ posts]

Send it to a shop. Get it diagnosed and then try it yourself. Atleast you wont be shooting in the dark.