Question about Kenwood KDC-MP528 CD Player

2 Answers

"Mystery" indicator and no audio

I just bought a car with an MP528 and it was working. It had a subwoofer and front and rear speakers, plus sub amp and another main speaker amp. I removed all this stuff and gave it to my grandson and after doing so I only wanted to connect it to the remaining front kick panel speakers, i.e. plain old stereo. After connecting the four speaker wires, the system no longer works (no audio).

I went into the menu and turned on the built-in amp, but still no audio. The tuner is apparently working as I get a stereo indicator when tuned to a valid station.

Also, on the upper left of the panel above the "volume" knob, there is a red indicator that is lit. It shows in the manual photos, but could find no mention of it anywhere to say what it's for. (Maybe it's telling me some kind of mute or error condition exists???)

Thanks,

Rick

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  • 7 more comments 
  • kermitdafrog Jun 19, 2008

    Solution #1 says "To find your solution CLICK HERE" where I didn't see a solution ... what am I missing?

  • kermitdafrog Jul 07, 2008

    Dave,



    Thanks for the reply, I appreciate it.



    More on the voltage measurements you mentioned, but I'll get the other stuff out of the way first:



    Since there was no mention of the red indicator anywhere in the manual, I broke down and asked a dealer, and he said the same thing as you did ... that it was a power on indicator ... which to me seems kind of redundant since everything else lights up anyway when it's powered on.



    The "ATT" I knew about from previous stereos over the years, (plus they mentioned it in the manual).



    Roger on the speaker wires. The four color groups coincide with the four speakers, with one from each pair having a tracer and the other one no tracer. The factory tags are still on each wire stating where they should go, and the manual agreed with the tags.



    I was pretty sure that the output amps float, so none of the speakers should be connected to chassis ground in any way, which I verified by disconnecting the speakers and measuring between them and ground with a VOM and verifying infinite. My two speakers are mounted to fiberglass kick panels anyway, so that need should be ok.



    I double checked the speakers to verify that they worked by disconnecting them and checking with a AA battery briefly across the leads to listen for the "pop", but just for grins I swapped to another pair of speakers.



    About the voltage measurements:



    You said to check for approximately 8 volts at each speaker wire ... would that be 8 volts across each pair, or from each wire to chassis ground? Also is that DC output with no signal? Is that with or without the speakers connected? 8 volts seems like an awfully high DC voltage to maintain constantly across a voice coil with nearly zero DC resistance.



    Thanks in advance,



    Rick

  • kermitdafrog Jul 07, 2008

    One more comment I forgot to mention:



    After using my guitar amp and verifying I was at least getting output from the line-out RCA jacks, (big impedance mismatch there) I bought a cheapie two channel amp ($20) from a pawn shop and that works so I least have a radio now, but I'd prefer to run it without an external amp. Since this is a 69 VW Beetle, I wanna keep all my luggage space.



    Rick

  • kermitdafrog Jul 07, 2008

    OK Dave, that makes sense now ... I just didn't know what the readings were referenced to. I'll check that this evening if I get a chance.



    Before I pulled out the external 4-ch amp and the sub amp and gave it to the grandson, the deck was using it's four pair of speaker wires to drive the 4-ch amp (the amp didn't have any RCA jacks).



    Not knowing any better, I was guessing that when the deck had it's internal amp turned off on the menu, that the speaker leads provided higher impedance line level out to drive the external amp instead of the usual low impedance high speaker level out. I was also thinking that the speaker leads may have still had line level output still available to drive the amp, but that the previous installer had maybe somehow fried the high power ic.



    Not being able to find anything else wrong that was obvious, and knowing that line level won't drive a speaker, and that I was getting audio out of those leads before, I thought it was "cockpit trouble" on my part.



    Lemmee check the lead voltages tonight and see if the amp ic is toast. I should be ok with soldering in a new ic provided the cost doesn't require a second mortgage.



    Thanks again,



    Rick



  • kermitdafrog Jul 07, 2008

    Dave,



    Thanks for the part number.



    I don't have any trouble with the theory part, (Ham radio 45 years) but with the "newer" microprocessor controlled, menu driven radios, I don't have a clue that when disconnected from power, does anything reset back to some kind of factory default state and disable the amps?, was the security stuff disabling it? Was I missing something in the menus? That sort of thing.



    Yup, your last paragraph brings up the same questions I have ... It was working before ... so I guess the obvious question to ask myself is "What changed?"



    Rick

  • kermitdafrog Jul 07, 2008



    Looks like Mouser has that amp for about $22

  • kermitdafrog Jul 07, 2008



    R R R WB8HNO DE WB5PDD

    dah dit dah

    dah dit dah

    dah dit dah



    Yeah, I guess "CQ" sticks with you for life. If you were General, you were doing CW at at least 13wpm. I think I got mine in the 9th grade. (WN5BIW Novice, then upgraded to WA5BIW General, let it expire while in the military, then later retested to my current WB5PDD General.) Back in our time there were five license classes; Novice, Technician, General, Advanced, and Extra. At my age I don't want to retest, so I keep mine current even though I'm rarely on the air.



    Voltages tomorrow ...



    Rick

  • kermitdafrog Jul 08, 2008

    Dave,



    I measured a little over a volt (1.4 - 1.7 I think it was) on each of the eight speaker wires to ground.



    I didn't hunt for a data sheet for the power amp IC so don't know how it's "wired" internally, but I'm wondering if the output stages were already toasted in the old installation before I removed it, and the drivers were bleeding through enough signal to drive the other amp, but not enough for speakers. I don't remember now if it had an input gain control like this cheapie I just bought. I might try connecting one of the rear speaker wire pairs, which I'm not using right now, to my guitar amp just to satisfy my curiosity.



    Rick

  • kermitdafrog Jul 09, 2008



    I have two solder suckers, two guns and three irons, plus a large hammer and pry bar, so one way or the other it'll come out.



    It probably won't be right away since funding for this project is further down the get it fixed list somewhere behind the lawnmower ignition module I ordered yesterday.



    I'll holler back when I do it and let you know if that does it.



    Rick

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Chet unkaufer always says murphys laws always apply

Posted on Jun 13, 2013

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The problem with the audio must be a problem with how the speakers are connected. You do not need to turn on the internal amplifier in this radio, it is always on. You said you connected the four speaker wires to the two speakers. You may have used the wrong wires. The front speaker wires from the radio are the white, white with black stripe for one speaker and the grey, grey with black stripe for the other front speaker. make sure each speaker you are connecting has the matching colors from the radio connected to it. meaning that one speaker will have a white wire and a white with black stripe wire, the other speaker will have the grey wire and the grey with black stripe wire. The purple and green wires should be seperated and insulated off from each other so that nothing can touch them that has any conductive surface.

The red led indicator is just for knowing that the radio is on. No other function for that. The muting for these is called "ATT" for attenuation and is located in the top left of the face.

make sure your speakers (terminals only) are not grounded to the chassis of the car, this can blow up the internal amplifier of the radio and this can result in no sound. If you can measure the voltage of the speaker wires coming out of the radio, they should measure at about 6 to 7 volts. If any one of the 8 speaker wires is not at that level, you have a blown amplifier IC in the radio. They all should measure the same give or take a few millivolts, if not the amp is bad.

Let me know if this help you at all. and a good rating would be appreciated for this free help.

Thanks,

Dave

Posted on Jul 06, 2008

  • 3 more comments 
  • Dave DeGain
    Dave DeGain Jul 07, 2008

    When you check the voltage of the speaker wire, they are 6 to 7 volts each wire when you have the ground lead of the meter grouned to chassis. Not from one wire to the other. Since the speaker wires will all have thst same voltage, it is no extra voltage across the voice coil. If you measure from one speaker wire to the other it will measure zero volts.



    Since the line out RCA's work, if there is no output from the internal amp, the output ic is bad. If you can solder, you can replace it easy. Let me know how the voltages check on the speaker wires.

  • Dave DeGain
    Dave DeGain Jul 07, 2008

    The part number for this IC is E-TDA7560A



    Since the amplifier had no RCA jacks for input, it had the speaker level input that you used. That means the speaker outputs are good if you had good quality sound using the speaker wires from the radio for the input to the amplifier. The speaker wires from the radio only have the high level output, they do not have a low level setting for input to an amplifier. The amplifier has an input just for speaker level and it brings that level from the speaker wires down to the proper level for input to the amp. I have not seen in a long time an amplifier that did not have an RCA input and only had a speaker level input. The speaker wires from the radio actually have a lower impedance but a higher voltage level output which makes it able to drive a speaker. The RCA jack outputs have a higher impedance but much lower voltage level which makes it good for input to an amplifier. The important thing to remember about these two different types of outputs is that the speaker wires have higher voltage output and in modern radios they have a floating ground at about 6 to 7 volts D/C. The RCA output is grounded at zero volts and sometimes even at the same point electrically as the chassis. The RCA max output level is normally about 300 millivolts A/C or 0.3 volts and the speaker wires output much more than that. The output signal is an A/C voltage but it rides on a D/C level.



    I am very concerned that you can get output from the amplifier using the speaker wires from the radio as input to the amp, but you get no sound from the speakers when the speaker wires from the radio are connected directly to the speakers. This really doesn't make much sense. After you measure the DC voltage at the speaker wires with the negative lead grounded to the chassis of the radio or the car, I should be able to get a clearer understanding of what might be going on. But if you get a signal from them to the amp, I got a feeling they will measure at the right level. Let's wait and see.



    Dave

  • Dave DeGain
    Dave DeGain Jul 07, 2008

    There is nothing in the menu system to have changed the output from the speaker leads. Those are always active, no way to turn them off.

    If you were using the speaker wires from the radio and had them going to an amplifier, and you had sound, then they seem to be working. The amplifier has a stage for speaker wire inputs to bring that level down to the proper level for an amplifier. The radio is not at the low level output at the speaker wires for an amplifier to use without some circuit that lowers the voltage of the speaker outputs. if the speaker wires at the radio output are making the amplifier work, that level at the radio is a high output level. It just gets lowered in the amplifier. That is what is bothering me, it should work with the speakers then. The radio has no setting for the speaker outputs to be changed from a high level output suitable for driving a speaker, to a low level output suitable for an input to an amplifier. The speaker outputs of the radio are always on, even if you are not using them and can not be turned off. They can be muted by a muting circuit, but if you have not muted it yourself, it will not happen unless you have a shorted muting transistor in the circuit. The muting is "Att" or attenuation circuit we discussed earlier. That can be defective, maybe just a coincidence it happened when the radio was taken out and re-installed in another car. I really would like to see those voltages at the speaker outputs before we try to figure out anyhting else. Just to make sure we are not chasing our tails on this. It could be very telling for me.

    I used to be a ham about 35 years ago, in high school. WB8HNO if I remember correctly. I had a general lic. I think it was called. One step above the novice or first level. I just have a hard time remembering now. But I do remember this:



    dah dit dah dit - dah dah dit dah



    Dave

  • Dave DeGain
    Dave DeGain Jul 08, 2008

    If you measures 1.4 to 1.7 volts of DC with your meter grounded to the chassis of the car or the chassis of the radio, you have a bad amp IC. it should be about 6.5 to 7.0 volts DC, it rides at that level so that it can go negative and positive about the same amount witht he AC signal. The AC signal is the audio. This is a circuit known as BTL circuit. It stands for a Balanced Transformer Less circuit. There is no need for a negative voltage supply if the signal is riding at about half way of the supply voltage (14.4 VDC in a car) A sound signal has a postive half of a cycle and a negative half of the cycle. If the speaker wires are at zero volts DC, the amp must produce a negative voltage to create the negative cycle of the sound wave. But if the relative ground is at half of the supply voltage, it can use just that postive voltage to create both the negative and positive cycle of the sound signal. Thus, no negative voltage needed, only positive.



    When you take out the old IC make sure to be careful and use some solder wick so you don't damage the circuit traces, and be sure not to create any solder bridges when you solder it back in.



    The radio comes apart pretty easy, if you need any help let know.



    Dave

  • keith Jun 13, 2013

    chet Unckefurr says murphys laws always apply

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