Hello, the display of my KDC-W534U car stereo no longer functions. Already checked the 2R7-resistors and one appears to be broken (infinite resistance).
Does anyone know the exact type of these resistors so I can solder in a new one? I think it is ERJ..something.., manufactured by panasonic. Many thanks.
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I also created a tutorial on fixing faceplates with 2R7 resistors (refer to my tip).
But, your unit will have a different chassis, as the faceplate is also a video display.
First you need to determine if the buttons on the faceplate are operating the various functions. If the buttons are NOT operating, then the faceplate itself (or connection to the main unit) can be considered faulty.
It's highly probable that the RIBBON cable (which connects faceplate to the inside of the unit) may be defective - this is common in some Kenwood units.
Try searching Google or youtube for ribbon cable repairs etc.
Yes, the problem is inside the main unit. I have fixed hundreds of these radios over the years.
The solder on these resistors get heat stressed and stop conducting properly. They just need a tiny little touch of solder.
With the radio in front of you and the face is facing you, take the top off and remove the CD mech. The CD mech can just be set over to the left a little and the ribbon cable to it can stay connected. Just move it out of the way gently. You will see a series of resistors in the right front corner area of the main board on top. They have 2R7 printed on them and there are quiite a few, all in that main area. Just resolder them and put it all back together again and the display will work normal.
Resolder all the resistors. They say 2.7 in the manual, but the print on the component is 2R7. For solder use 60-40 rosin core with flux. The thickness should be a small diameter, but most any solder will work, you will only be putting a very small dab of solder on each solder connection. Just enough to make it melt and reflow, no more. This is no guarantee that it will fix your unit, but it is the most common cause. You may find that the display being out for yours is something different. If you have a voltmeter you can put the radio on a bench and check the voltages (DC) on those resistors when it is powered on. You will need a small power supply capable of about 3 amps to power up a car stereo. I don't remember what the voltage are supposed to be, but you should start at one end and have a high voltage and as you go from one resistor to another, the voltage will go down in equal increments. It is a voltage ladder and with all the resistors being the same value, you should have the same voltage across each resistor.
The first thing to check would be the voltages on the speaker wires. They should be about 6.5 to 7 volts on each wire. Then check the surface mounted resistors on the front right side of the main board. Take out the CD deck and reflow the solder on them. Make sure you do this part with no power source connected. The surface mounted resistors have "2R7" on the top of them and are located in the right front as mentioned before, while looking at the unit from the front facing you. If you do not find the surface mounted resistors it could be that I am thinking of another model of Kenwood, but I am pretty sure they are also in this model as well. Use just a touch of solder on each side of the resistors, there are about 6 to 8 of them all connected in series. After that, reconnect the CD deck and connect the power source to the red and yellow wires and the black wire is your ground, connect that as well. The display should light up. Let me know what you come up with on the voltages of the speaker wires and if the display starts working again. I do not have access to my service manuals at this time, it may be about 2 weeks before I can get them. So I may not be able to get you completely fixed up until I can get my service manuals. A schematic is sometimes the most valuable tool when fixing electronics.