My new amp repair project Harman Kardon CA5250

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Alfaholic
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My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

Hi i wonder if anyone of you have any experience with the harman kardon car amplifiers, i got a broken CA5250 that got snow inside and the fuse went out.
Its a real big amplifier and it looks good and since all my amplifiers have new caps and works perfect i needed a new project, i payed 30$ + shipping for it so i should be able to make a profit on it.
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Re: My new amp repair project Harman Kardon CA5250

Post by vwdude »

I've never seen one of those. I wonder if that's an infinity or JBL? Harman owns both of those other companies.
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Re: My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

vwdude wrote:I've never seen one of those. I wonder if that's an infinity or JBL? Harman owns both of those other companies.
They were sold 2010-2012 in Norway then Harman Kardon stopped making them now they make oem stereo for BMW etc, they sound good for a 5 channel amp i see it got high scores when it was tested.
I dont think im going to use it but i will repair it and store it away, im trying to get a new plexi for the top but i think its easy to make one for it if i cant find one new.
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Re: My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

I bough another one today its a four channel harman kardon ca470 this is in working order i gave the seller a low bid because it has been for sale the last two months without getting sold i payed 40$ with shipping included.
They look nice these amplifiers i like them but not as much as my pg amps
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Re: My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

Well today i picked up the HK CA5250 does anyone know what is most likley to blow when an amplifier gets water inside?
The protect light is on but i cant see anything wrong with it so im going to test it with my brand new auto DMM, just wanted to here if anyone knew where i should start checking.
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Re: My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

Hi guys, i have removed all the mosfet transistors several of them where broken but i read somewhere that small smd resistors also can blow when the transistors blow.
Since im clueless i need your help to be honest i dont know what those small smd are i see some are resistors and some are transistors but the ones im havin problems with are the ones that only have colour not any writing on them.
What i need to know is the names on them and how i find them at digi key so i can order the ones that are blown, the biggest problem is that i dont know the names on them that makes it hard finding info about them.
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Re: My new amp repair project Harman Kardon CA5250

Post by vwdude »

They look like pico fuses but I've seen resistors that look like that too. I'm pretty sure those are the gate resistors. I think yet are called surface mount resistors rather than 'through hole' resistors. The number on them is a code, I'm sure a google search to decode them will yield the info you need on values...I'll see what I can find for sure.

Ok so upon further inspect, in your second to last photo those are se sisters (hence the "R" number). In the second a few of those are capacitors I think (C numbers) but the blown one is something else, that 'L' is something that I don't recognize. Those can be a pain to replace because of how small they are.
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Re: My new amp repair project Harman Kardon CA5250

Post by trickyricky »

Were any of the power supply fets bad? You probably removed them without needing to.
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Re: My new amp repair project Harman Kardon CA5250

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trickyricky wrote:Were any of the power supply fets bad? You probably removed them without needing to.
There was four bad power supply fets but i was not sure if i had to remove them to check them since they are connected to each other, i removed them all after i marked where they where mounted.
The ones with colour with the power terminal are smd capacitor they are light orange in colour, im going to order a set but they are listed after what size they are and i dont got a clue if they are 0805,1206 or 0603.
Im reading on the www.bcae1.com site he says that if the power fets are broken the smd resistors also can fail, my biggest problem is finding the right parts im thinking of asking Harman Kardon if they can share blueprint of the amplifier with me.
Thanks for the help guys :-)
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Re: My new amp repair project Harman Kardon CA5250

Post by Bertje »

For smd parts you can use a smd codebook like http://www.marsport.org.uk/smd/mainframe.htm. Sometimes transistors are difficult to find. Try to get the power supply working first. Just remove the rectifiers after the torroids, then you can test the power supply without any load.
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Re: My new amp repair project Harman Kardon CA5250

Post by trickyricky »

0805,1206 or 0603 are just the size of the smd resistors...in order to know which one you need to order you'll have to measure the original with a caliper.


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Re: My new amp repair project Harman Kardon CA5250

Post by trickyricky »

If one of the power supply fets failed...replace them all as well as their gate resistors and predrivers. It's also not a bad idea to replace the PWM IC while your at it.
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Re: My new amp repair project Harman Kardon CA5250

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trickyricky wrote:If one of the power supply fets failed...replace them all as well as their gate resistors and predrivers. It's also not a bad idea to replace the PWM IC while your at it.
Thanks for your help, i have measured the gate resistors and they are all have the right value but im ordering different kits with them so i can change them and the smd capacitor
that is blown.
Im not looking forward to changing these smd resistors and capacitor they are 0608, the water that has come inside the amlifier has gone down the side with the power supply fets.
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Re: My new amp repair project Harman Kardon CA5250

Post by Bertje »

Just clean the board with IPA and carefully test it without a load.
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Re: My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

Bertje wrote:Just clean the board with IPA and carefully test it without a load.
Tha board is out of the chasis and the fets are removed, when i powered it up the protection light comes on because
water came inside the amplifier the water was spilled a year ago.
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Re: My new amp repair project Harman Kardon CA5250

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Well i have orderd all the fets,small transistors, smd resistors/capacitors and new caps for input and rail, its expensive so i hope i can get it to work.
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Re: My new amp repair project Harman Kardon CA5250

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If not at least you will have some nice wall art.
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Re: My new amp repair project Harman Kardon CA5250

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vwdude wrote:If not at least you will have some nice wall art.
Nice and expensive wall art lol, i know im going to get it to work its just a matter on what its going to cost but if i learn something new
i dont care i have tested everything multiple times and everything seems to be ok.¨
On the sdt-ti r-link box i changed many different items but in the end it was a a pin soldiered together on the input rj45 connector, i learened much from it
and i think im much better when it comes to testing different transistors and resistors.
On this amplifier many of the small smd capacitors and transistors are without markings on them and that makes it hard finding datasheet to see how it works,
I have been lucky that trickyricky has helped me with answering many of my questions im also reading very much online about amplifier repairs.
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Re: My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

Hello, im just finished with changing all the fets and transistors and im putting the amp back together.
There is a long slice of sillypad and some of the fets had cooling paste on them, my question is if i can use cooling paste on all the fets?.
I always use some small spots of cooling paste unde the sillypad so it stick and does not slide, i hope the damn thing works fingers crossed.
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Re: My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

Well i tried to power it up and its still got problems, before it stayed in protect but now the power light goes on but then goes of and the amplifier goes in to protect
it keeps on going from power to protect and i got 4-12v on the subwoofer channel.
I think the problem is to much volt to the subwoofer channel i will read more about what may be the cause but its better then it was.
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Re: My new amp repair project Harman Kardon CA5250

Post by trickyricky »

DC? anything above 0.5vdc should trigger the dc protection circuit.
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Re: My new amp repair project Harman Kardon CA5250

Post by Alfaholic »

trickyricky wrote:DC? anything above 0.5vdc should trigger the dc protection circuit.
Yup, it tries starting up but the volt goes up on the sub channel and it goes in protect mode, i checked caps they have contact and
the caps are mounted the right way.
I changed all the fets and im waiting on the small smd resistors and capacitors, what can cause this im thinking bad connection but i measured
almost everything after i soldered inn the new parts.
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