# How is this amp still working ??



## anthonyott99 (Mar 21, 2011)

I purchased this amp for 20 bucks, i was told it worked, so i powered it up with 12 volts, green light came on, plugged my home audio rca's into it and it has output using a multimeter an both channels and bridged, but this is what i found inside. how is this amp working ??


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## ATOMICTECH62 (Jan 24, 2009)

It wont work correctly.It will be missing one side of the rail voltage so only half of the wave form will be produced.


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## anthonyott99 (Mar 21, 2011)

ATOMICTECH62 said:


> It wont work correctly.It will be missing one side of the rail voltage so only half of the wave form will be produced.


Sorry, i am a total noob to this, so will one channel work ? Or will it not be a useable amp at all ?? can those diodes be replaced or is the board fried ??


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## ATOMICTECH62 (Jan 24, 2009)

Sorry,but if you do get any music out of it it will be very distorted on all channels.
It looks like a Power Acoustik or similar, so its not really worth repairing.


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## anthonyott99 (Mar 21, 2011)

ATOMICTECH62 said:


> Sorry,but if you do get any music out of it it will be very distorted on all channels.
> It looks like a Power Acoustik or similar, so its not really worth repairing.


Thanks for being honest man, just for sh**'s and giggles, is replacing those diodes what needs to be done to repair or is it more in-depth than that ??


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## ATOMICTECH62 (Jan 24, 2009)

Those 3 pin burnt pieces are mosfets.Probably IRFZ44n's.There is 5 resistors that will also need replaced(burnt)Probably 100 ohms.Then,without using a scope the verify a good waveform you will also need to replace the 2 small gate drive transistors and the 16 pin TL494 PWM chip along with the 5 mosfets on the other side of the board.If all these parts are not replaced,when the amp is turned on the first time it might explode again.


You will first have to check all the channels for shorted output transistors.This is probably why it blew and it will blow again as soon as power is applied.


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## anthonyott99 (Mar 21, 2011)

Wow, thanks a lot for the info, i always wanted to try to repair an amp, and a cheap one like this would be a good test subject if i decide to do so, i really appreciate the help, if i decide to try to repair i will post up ! Thanks again !


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## ATOMICTECH62 (Jan 24, 2009)

Q27 and Q28 are the transistors I mentioned earlier.


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## anthonyott99 (Mar 21, 2011)

ATOMICTECH62 said:


> Those 3 pin burnt pieces are mosfets.Probably IRFZ44n's.There is 5 resistors that will also need replaced(burnt)Probably 100 ohms.Then,without using a scope the verify a good waveform you will also need to replace the 2 small gate drive transistors and the 16 pin TL494 PWM chip along with the 5 mosfets on the other side of the board.If all these parts are not replaced,when the amp is turned on the first time it might explode again.
> 
> 
> You will first have to check all the channels for shorted output transistors.This is probably why it blew and it will blow again as soon as power is applied.


Seriously considering replacing all these and seeing whats up, would be a great first amp repair project !!!


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## anthonyott99 (Mar 21, 2011)

what part number or kind of resistors would i need to replace the burnt ones ?? what about the q27 and q28 ones ?


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## ATOMICTECH62 (Jan 24, 2009)

Q27 and 28 will have the #'s on them and the 5 burnt resistors look like 1/4 watt 100 ohm.
Look at the 5 mosfets and resistors on the other side of the board.The resistors should be brown,black,brown and the mosfets should be IRFZ44's ,48's,46's,34's.


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## anthonyott99 (Mar 21, 2011)

ATOMICTECH62 said:


> Q27 and 28 will have the #'s on them and the 5 burnt resistors look like 1/4 watt 100 ohm.
> Look at the 5 mosfets and resistors on the other side of the board.The resistors should be brown,black,brown and the mosfets should be IRFZ44's ,48's,46's,34's.


really appreciate this info !! I am going to try this !!


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## anthonyott99 (Mar 21, 2011)

now i just need to study up on the actual process of replacing and soldering them in !! 
Thanks again !!


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## anthonyott99 (Mar 21, 2011)

did you mean Q26 and Q27 ???

















Q28 is one of those Mosfets and they are the 1RFZ48n's, 

Thanks again !!


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## anthonyott99 (Mar 21, 2011)

Also, my chip is listed as a K1A 494 AP chip, will the Tl 494 pwm chip be the replacement ??. Also you said to : You will first have to check all the channels for shorted output transistors.This is probably why it blew and it will blow again as soon as power is applied., , , How do i do this ?? Sorry, know a lot of questions but want to make sure its right when it goes back together. Thanks in advance for any help !!!


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## anthonyott99 (Mar 21, 2011)

Additional info : had a friend decide he wanted t see what the amp would do and hooked it up to his two Kicker 12s and it pushed them with plenty of power, better than his actually but it does have a low hum to it when the source is turned down, and when the decibel switch is on +18 instead of 0 it has a lot of distortion, but hearing it , i think i am going to repair it, its almost usable now, just not on full power.


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## vwdave (Jun 12, 2013)

That wasn't smart on his part as his subs could have blown or at least been damaged.

I would replace the caps too. Check the measurements and find comparable sized caps with the same voltage and temp ratings. Chances are you will get high farad rating. Also, with resistors. Get 1% tolerance ones and it will be better quality parts than from the factory.


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## miniSQ (Aug 4, 2009)

vwdave said:


> That wasn't smart on his part as his subs could have blown or at least been damaged.
> 
> I would replace the caps too. Check the measurements and find comparable sized caps with the same voltage and temp ratings. Chances are you will get high farad rating. Also, with resistors. Get 1% tolerance ones and it will be better quality parts than from the factory.


you beat me too it..i was going to say hook up any speakers to this amp that you are fond of


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## anthonyott99 (Mar 21, 2011)

Where is the best place to get these parts ? I found the 100 ohm resistors on Ebay but having a little trouble with the mosfets, only a few available online, thought maybe yall would know a better resource ?? Are the mosfets interchangeable, the 44's in place of the 48's or do i need to stay with the 48's ??


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## anthonyott99 (Mar 21, 2011)

miniSQ said:


> you beat me too it..i was going to say hook up any speakers to this amp that you are fond of


Believe me, i warned him, i don't know what he was thinking.


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## TrickyRicky (Apr 5, 2009)

Mouser, arrow electronics, Digikey, MCM are just a few that I buy my components from. You might want to avoid ebay as there are many counterfeit components listed.


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## ATOMICTECH62 (Jan 24, 2009)

You need to use the 48's or,better yet replace all 10 48' with IRF3205 and replace the10 100 ohm resistors with 47 ohm ones.Sorry I meant to say Q27 and Q26 not 28 in the earlier post.Yes a TL494 is the same part.
If you by Mosfets from Ebay try to get them from "activeparts"he sells real stuff not the counterfeit junk that has flooded Ebay.
If the amp is producing sound then the channels might be ok.But to test the output transistors put one test lead from the meter on the middle leg and check ohms with the other test lead on the right leg and then the left leg.If you get anything under a few thousand ohms(like 1,10,350 for example) its probably defective.


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## anthonyott99 (Mar 21, 2011)

ATOMICTECH62 said:


> You need to use the 48's or,better yet replace all 10 48' with IRF3205 and replace the10 100 ohm resistors with 47 ohm ones.Sorry I meant to say Q27 and Q26 not 28 in the earlier post.Yes a TL494 is the same part.
> If you by Mosfets from Ebay try to get them from "activeparts"he sells real stuff not the counterfeit junk that has flooded Ebay.
> If the amp is producing sound then the channels might be ok.But to test the output transistors put one test lead from the meter on the middle leg and check ohms with the other test lead on the right leg and then the left leg.If you get anything under a few thousand ohms(like 1,10,350 for example) its probably defective.


I was going to replace all 10 48's so i will take your advice and order the IRF3205's and i was also planning on replacing all the 100 ohm resistors, so i will also take your advice and do the 47 ohm ones, what will be the advantage of replacing these with the ones you suggested ?? i am also going to order the TL494, and replace the Q27 and 26, believe that part number was an A1023 on both, i have really appreciated your help !!

The 47 ohm resistors are 1/4 watt correct ATOMIC ???


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## ATOMICTECH62 (Jan 24, 2009)

Yes they are 1/4 watt.The 3205 are 50%more heavy duty so they need a lower ohm resistor to over come the gate capacitance and Miller effect.
The 48's are older and usually cost more then the 3205's so I just upgrade the amp when possible.Activeparts sells the 3205's for about $1 each and he ships fast.


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## TrickyRicky (Apr 5, 2009)

Have to give a big thanks to Atomic for the hook up with the 3205's. They're a bit cheaper than Mouser. Thanks.


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## dealer (Jul 31, 2013)

TrickyRicky said:


> Have to give a big thanks to Atomic for the hook up with the 3205's. They're a bit cheaper than Mouser. Thanks.


Yes, he is definitely giving out some top notch advice. 3205's are much more reliable and over 100 amps current capability if I remember correctly. In some circuits depending on how many per mosfet driver, 22 ohms worked better as the resistor, but 47 would work great in this amp, and in most as a rule of thumb. 3205 very forgiving vs something like an ndp7060, ugh.


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## anthonyott99 (Mar 21, 2011)

Yes, I am very fortunate to recieve such sound advice on my first venture into amp repair, the next thing is to find the right soldering iron in my budget, can't really afford a station right now


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## GlasSman (Nov 14, 2006)

anthonyott99 said:


> Yes, I am very fortunate to recieve such sound advice on my first venture into amp repair, the next thing is to find the right soldering iron in my budget, can't really afford a station right now


Suggestion.....watch as many amp repair vids on Youtube as possible.....then asked the important/strategic questions once you have a good base knowledge.

This project will cost more than it's worth....but you _*should*_ walk away learning a good amount about amp repair.


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## ndramountanis (Apr 23, 2013)

Can you just put the magic smoke back in lol...It's nice when you can see the damage... Sometimes its a guessing game..


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## anthonyott99 (Mar 21, 2011)

yeah it looks like a pretty straight forward repair thanks to the advice and parts list i was given, believe it or not, it will push a couple of 12's right now pretty darn good with gain turned down a little, when it turned up you get some distortion with the source turned off, cant wait till the Holidays when i have some time off to start working on this thing ! Thanks everyone !!


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## helpmeplease (Oct 6, 2012)

vwdave said:


> That wasn't smart on his part as his subs could have blown or at least been damaged.
> 
> I would replace the caps too. Check the measurements and find comparable sized caps with the same voltage and temp ratings. Chances are you will get high farad rating. Also, with resistors. Get 1% tolerance ones and it will be better quality parts than from the factory.


They are just kickers


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