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Using Arduino => General Electronics => Topic started by: squall2005 on Oct 02, 2012, 06:56 pm

Title: Need help with a car amp
Post by: squall2005 on Oct 02, 2012, 06:56 pm
I'm working on a car amp for a friend, the problem with it is a resistor that burnt out. My problem however is that it is too badly burnt to determine what size or was, is there any way to determine what size resistor I should replace it with? Thanks in advance for any kind of help!
Title: Re: Need help with a car amp
Post by: MarkT on Oct 02, 2012, 06:58 pm
Knowing where it is in the circuit and what it is for would help - photos would be great.  It could be burnt out because something else burnt out of course...
Title: Re: Need help with a car amp
Post by: johnwasser on Oct 02, 2012, 08:02 pm
If it is a stereo amplifier you may find that the other channel has a matching resistor.
Title: Re: Need help with a car amp
Post by: Docedison on Oct 02, 2012, 10:46 pm
It is considered good form to post a drawing and an accurate description of the problem. That having been said for the sake of saying it... If both channels are inoperative then It's likely the problem is in the power  supply. If one channel is blown the chances are that you have an identical, hopefully ok resistor in the other 'working? (You didn't state...) Channel. I have had occasion to service many of those devices over the years. Typically the "Amplifier" will have 2, 25 to 500? watt amplifiers and some means of isolating the dc input and increasing it's voltage, usually a power oscillator and transformer or power multivibrator of some kind and generally it's the Power Supply that fails. Some investigative work with a DMM should straightaway put you on to the bad parts, a slightly scorched smell may well be present too and is a good indicator of parts that have been stressed..

Bob
Title: Re: Need help with a car amp
Post by: johnwasser on Oct 02, 2012, 11:33 pm

Some investigative work with a DMM should straightaway put you on to the bad parts, a slightly scorched smell may well be present too and is a good indicator of parts that have been stressed..


He knows where the burned-beyond-recognition resistor is.  He wanted help figuring out the correct replacement value.

Oh, one other option:  If the resistor is near an identifiable chip you might find the application notes for that chip provide a recommended value for that resistor.
Title: Re: Need help with a car amp
Post by: DVDdoug on Oct 03, 2012, 01:25 am
Quote
...the problem with it is a resistor that burnt out.
Most-likely, that's not the only problem.  Resistors don't usually burn-up by themselves.   Usually, a semiconductor overheats, dies, and shorts-out dies.  Then the excess current caused by the shorted semiconductor might burn-up something else.
Title: Re: Need help with a car amp
Post by: SirNickity on Oct 03, 2012, 04:28 am
True that.  All but the smallest car audio amps require necessarily complicated switching PSUs to upscale the rail voltages.  Unless you're experienced and well equipped with scopes and whatnot, you might be better off sending it to a repair shop.  Not that it isn't worth a shot if you're determined to learn, just be careful and expect to do more damage than good while poking around.
Title: Re: Need help with a car amp
Post by: squall2005 on Oct 09, 2012, 05:29 am
I truly appreciate all the responses, I haven't been able to access my account for awhile. I looked up the specs, and I'm still really new to electronic boards. So these details you guys have been giving really help, but I digress, the specs:

# of Channels    2 (Stereo)
RMS Power (Watts)    700 x 2 @ 2
Max Power (Watts)    1100
Circuit Type    MOSFET
Car Amplifier Features    Bridgeable, Crossover
Inputs    RCA
It's the r532 resistor and google searches failed me on this, so I had to turn to further help. I'll try to get a pic of it up as soon as I can.
Title: Re: Need help with a car amp
Post by: squall2005 on Oct 09, 2012, 05:31 am
And I did completely fail to mention but it's an interfire IB 2900.
Title: Re: Need help with a car amp
Post by: retrolefty on Oct 09, 2012, 06:59 am

And I did completely fail to mention but it's an interfire IB 2900.


The bigger problem is that you really need to determine first what caused the resistor to burn out before you replace it, even if and when you do find out the ohm and wattage rating for it. Without a schematic drawing and some experience with electronics troubleshooting, it's normally not the case that a simple resistor change will fix the problem. The more likely outcome will just be that the new resistor will burn up. What will your plan be if and when that more likely thing happens?

Lefty
Title: Re: Need help with a car amp
Post by: squall2005 on Oct 09, 2012, 07:29 am
Well to be honest I'll have to cross that bridge when I get to it