Kenwood KDC-MP825 head Unit repair - diyAudio
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Old 7th November 2007, 09:14 PM   #1
leko916 is offline leko916  United States
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Default Kenwood KDC-MP825 head Unit repair

Hello,

I am new but this looks like a great forum, very informative.

I have a Kenwood head unit KDC-MP825. the other day I had it on and it suddenly stopped sending any signal to the speakers. It still appears to work fine (CD's play, HD Radio tunes, ETC) and I still get signal to the sub from the pre-amp out so this makes me think the internal amp is toast. All fuses (that I can find) check out, and after having opened the unit nothing appears to be overloaded, burnt, loose etc.

I was told the problem is probably in the amp IC. I see 2 main IC's on the board, and in between them I see 2 terminals labeled TEST which I figure is where I need to start but I want some professional advice before I go poking around with my DMM.

I was quoted ~100.00 to have it repaired but I figure with some guidance I can get it sorted out. I found a website with IC's for this unit for about 12.00 each. I have plenty of electrical background and some electronics.

Thanks for any help and guidance you can offer.

Pics: http://www.robbrenner.com/kenwood.htm give it a minute to load, I uploaded them to my site in full-res.

Rob
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Old 7th November 2007, 11:52 PM   #2
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The internal amplifier is going to be mounted to the heatsink and will have ~25 pins.

Have you tried disconnecting all of the speaker wires from the head unit and using a test speaker to check the amplifier's output? If a speaker wire shorted to the chassis ground somewhere, the amplifier may have shut down to protect itself.
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Old 8th November 2007, 02:29 AM   #3
leko916 is offline leko916  United States
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Sorry, forgot to say I replaced the stock head unit and it works fine.

I also metered the speaker outputs to car chassis ground, on 2 channels I got +11.6v and on 2 outputs I got +1.4v.

Power supply is fine from the car, +12v con. is 13.8v and +12v ign. is 13.8v.
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Old 8th November 2007, 02:57 AM   #4
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It appears that the IC has failed.

If you decide to replace it, you need to be careful when removing the old IC from the board. I'd suggest using a razor knife or a pair of fine tipped cutters to cut the leads at the body of the IC. If you use a razor knife, you'd make several passes on the legs where they enter the body of the audio amplifier IC.

After separating the body from the leads, you can remove the leads individually. Apply new solder to the connection and then pull the lead (very gently) while heating the solder joint. Then clean the holes with a desoldering tool or desoldering braid (but not the stuff from radio shack).

Apply heatsink compound to the IC before replacing the heatsink.
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Old 8th November 2007, 09:10 PM   #5
leko916 is offline leko916  United States
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To make sure I am looking at the right IC (sorry for my newbi-ness) it looks like it is IC4, on the back of the unit (was clamped to the heat-sink) and is marked as;

ST
TDA7560
H22CR0417
MALTA
0.4

And has 25 pins as mentioned above. If thats the case, any advice on where to find a replacement?

I found:

PartStore.com which lists that part as
analog IC 2019v ($34.29)

But on KenwoodParts.com its listed as
TDA7560 Power IC ($34.29)
OR
E-TDA7560A Power IC ($30.26)

Neither of which have the KDC-MP825 listed under models they fit.

Thanks for your continued help.

Rob
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Old 8th November 2007, 09:27 PM   #6
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Looks like it's available at the usual distributors. Both DigiKey and Mouser carry it and have it currently in stock for about $22. It seems that this IC is available only in the one package, so if that's how the dead one is marked, the replacement should fit. Since this part seems to be easy to get, I wouldn't recommend using one of the 'part search' type vendors. They tend to jack up prices and aren't as reputable.
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Old 8th November 2007, 09:53 PM   #7
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http://www.mcminone.com/product.asp?...me=MCMProducts
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Old 9th November 2007, 01:08 AM   #8
ppia600 is offline ppia600  United States
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Are you absolutely sure it is not a grounded or shorted speaker problem? Most oem decks don't have short/ground protection and will keep playing even if one of the speakers or speaker wires is having issues. Aftermarket decks are getting better though, and most have protection and some even tell you which speaker is the culprit on the screen.
Also check pacific coast parts distributors, they have kenwood parts for good prices
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Old 9th November 2007, 01:19 AM   #9
Flyin11 is offline Flyin11  United States
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Kenwood are a good brand of radio but I have seen reports and have had it happen to me with my last receiver. The internal amplifiers tend to die out for some reason..?? It's the reason I had to get a new radio 2 years ago..My old Kenwood had the same thing happen...No highs but I had lows. It burnt out on me. Be careful with the MP series as well...I have experiences now with it overheating with my MP4028. If you play it very loud for a long period of time, the highs will fade down and then back up again and the only way to stop it is to turn it down and let it cool down. I've seen reports on Yahoo all over the net about people with the same issue. I hate to say it but my next HU more than likely will not be another Kenwood (Unless maybe a Excelon in which someone had said he had no issues after changing from his MP series). Other than that, I might look into a Alpine or Pioneer....Dern internal amplifiers
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Old 9th November 2007, 01:26 AM   #10
ppia600 is offline ppia600  United States
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Maybe he should also check for pins on the amp ic that may have cracked loose from the board. Some of the older decks had issues with that as well. Yeah, we had a few kenwoods come back with the no audio issue, but most of them were under warranty so I didn't get to fiddle with them.
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