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The 560sel that I bought recently had a tired Blaupunkt Tokyo in the dash with an amp in the trunk and subwoofers. Yesterday I pulled the old radio and installed a new Blaupunkt unit. Connectors and layout are the same on both units, so I just plugged things back the way they were.

I realized something when playing with the balance adjustment - all speakers play sound from the right channel, that is, mono. I don't know how the PO wired everything up, though there was the minimum of hacking, thank God.

Maybe a few of you have dealt with this before. I am wondering if the PO wired the subwoofer to the left channel only, or if the problem lies with the fader control, which was not wired around. Thanks guys and gals-
 

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Had same problem

The 560sel that I bought recently had a tired Blaupunkt Tokyo in the dash with an amp in the trunk and subwoofers. Yesterday I pulled the old radio and installed a new Blaupunkt unit. Connectors and layout are the same on both units, so I just plugged things back the way they were.

I realized something when playing with the balance adjustment - all speakers play sound from the right channel, that is, mono. I don't know how the PO wired everything up, though there was the minimum of hacking, thank God.

Maybe a few of you have dealt with this before. I am wondering if the PO wired the subwoofer to the left channel only, or if the problem lies with the fader control, which was not wired around. Thanks guys and gals-
It was a faulty fader switch.
 

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Discussion Starter #3
I pulled the radio and studied the wiring for over and hour... It looks like all the speakers are hooked up to the Right Rear output. It has an amp in the trunk that was meant to only drive the subwoofer. Is there a way to hook up the Blaupunkt to the factory wiring harness, which is still intact, and have stereo sound coming out of all the speakers? It seems like you could wire into the fader control harness and achieve that, except I don't know what to do with the separate + and - wires of the radio output.

I am also halfheartedly considering pulling new wire. I've read several posts on the great results, but no DIY instructions. It seems like you would need to remove seats and consoles, a big PITA. If I could do it in a weekend, I might do it.
 

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I have an 89, like you do. I had a similar problem but with all factory parts. In my case the one amp under the rear seats was bad, replaced it and all speakers work again. Not sure what they did in your case, if they mucked with the wiring behind the head unit that could well be your problem. But if you are going to pull the seats anyway, may as well check those amps out. One on each side.
 

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I pulled the radio and studied the wiring for over and hour... It looks like all the speakers are hooked up to the Right Rear output. It has an amp in the trunk that was meant to only drive the subwoofer. Is there a way to hook up the Blaupunkt to the factory wiring harness, which is still intact, and have stereo sound coming out of all the speakers? It seems like you could wire into the fader control harness and achieve that, except I don't know what to do with the separate + and - wires of the radio output.

I am also halfheartedly considering pulling new wire. I've read several posts on the great results, but no DIY instructions. It seems like you would need to remove seats and consoles, a big PITA. If I could do it in a weekend, I might do it.
I would search the forum, or go to Jonathans blueridgemb site for the audio install / wiring write up.
Swapping the rear amps sounds like an easy way to find out whether one of them is faulty.
Cheers
 

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Discussion Starter #6
I have an 89, like you do. I had a similar problem but with all factory parts. In my case the one amp under the rear seats was bad, replaced it and all speakers work again. Not sure what they did in your case, if they mucked with the wiring behind the head unit that could well be your problem. But if you are going to pull the seats anyway, may as well check those amps out. One on each side.
I don't think that is the problem - on the existing splices for the old Blaupunkt head unit, only the RR channel from the receiver is hooked into the harness. The LR, LF, and RF are capped off, so in essence, all the speakers are being fed by the RR channel from the head unit. I had thought that the sound seemed mono and I was right.

The way the wiring was done is very confusing and I don't know if the old Becker amps behind the rear seat are in the circuit at all. I have pulled the rear seat on my 300SE a few times and it was a breeze. I am not sure how to pull a 560SEL rear seat though.

It would be far easier to purchase and install an original Becker 780 but I want to be able to play CD's and this new Blaupunkt unit is very nice and looks appropriate in my car.
 

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It sounds like you Blaupunkt radio has an internal fader as it had four ouputs (right front, left front, right rear and left rear). Your original Becker only put out stereo and used the external fader swith to balance front and back.

To feed your amplifiers, you need to use the pre-outs from the head unit. If you send the amplified signal to your Becker amps you risk frying them, or blow the speakers.

Test the outputs from the Blaupunkt unit by hooking a speaker directly to the unit. If you get normal sound, the unit has an internal amp and should not be used with the Becker components.
 

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Discussion Starter #8 (Edited)
It sounds like you Blaupunkt radio has an internal fader as it had four ouputs (right front, left front, right rear and left rear). Your original Becker only put out stereo and used the external fader swith to balance front and back.

To feed your amplifiers, you need to use the pre-outs from the head unit. If you send the amplified signal to your Becker amps you risk frying them, or blow the speakers.

Test the outputs from the Blaupunkt unit by hooking a speaker directly to the unit. If you get normal sound, the unit has an internal amp and should not be used with the Becker components.
Hey Axel,
The Blaupunkt indeed has internal fader control. When playing with the balance control, however, I realized that the speakers all are fed by the right channel, and after studying the wiring mess, only the right rear channel from the head unit.

I believe that the Becker wires and amps are intact, the installer tapped into them without cutting. He sure did take the easy out on most of it.

I have studied the Mercedes wiring diagram and looked at the fader control plug. If I'm right, I could tap into the E1(front left) and A1(rear left), and the E2(front right) and A2(rear right) wires and get sound to all speakers with no rewiring. Is that correct? How would I wire the + and - wires from the head unit? It does have pre-amp out for all 4 channels.
 

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If the Blaupunkt unit has pre-outs (line-level, as it is also known) and you want to use the rest of the Becker system, you need only to locate the left and right outputs and hook those up to the OEM wiring. With the left and right stereo signal going to the rear amps and the fader control in the center console, you should be all set.
 

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Discussion Starter #10
If the Blaupunkt unit has pre-outs (line-level, as it is also known) and you want to use the rest of the Becker system, you need only to locate the left and right outputs and hook those up to the OEM wiring. With the left and right stereo signal going to the rear amps and the fader control in the center console, you should be all set.
Even at pre-amp level, it is divided into RF, RR, LF, LR. Which should I chose-front or rear?
 

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Even at pre-amp level, it is divided into RF, RR, LF, LR. Which should I chose-front or rear?
It doesn't matter.

Just pick front or rear and set the head-unit's internal fader all the way to whichever you choose.
 

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Discussion Starter #12
Sounds easy enough, Axel. The four pre-amp outputs are RCA female plugs. I would get an adapter that has a male RCA plug on one end and two wires on the other. Which wire would I use to tap into the Becker harness - red (+) or black (-)?

A big thank you for your advise and wisdom!
 

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The four pre-amp outputs are RCA female plugs. I would get an adapter that has a male RCA plug on one end and two wires on the other. Which wire would I use to tap into the Becker harness - red (+) or black (-)?
Hmmmm......

An RCA plug is neither positive nor negative. The center plug(hole) is the connector for the signal and the outer ring provides grounding between the two components.

The audio signal is DC unitl the final amplification stage where AC is needed to drive the speakers. So pre-outs are low voltage DC signals.

The Becker amplifier input cables are therefore not +/-, they're left or right and obviously don't have the grounding function.
 

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Discussion Starter #14
Hmmmm......

An RCA plug is neither positive nor negative. The center plug(hole) is the connector for the signal and the outer ring provides grounding between the two components.

The audio signal is DC unitl the final amplification stage where AC is needed to drive the speakers. So pre-outs are low voltage DC signals.

The Becker amplifier input cables are therefore not +/-, they're left or right and obviously don't have the grounding function.
A knuckle-headed question on my part...I realized the answer after I posted it.
 

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Discussion Starter #15
IT IS DONE! I deciphered the mess of spaghetti from a previous half-a**ed installation and have stereo tunes from my new Blaupunkt receiver. The help I received from AxelWulff and Mercedes wiring diagrams was invaluable.

What I ended up doing is connecting the new receiver to the Becker wiring harness/amps via the preamp out. The preamp out had RCA plugs, which I cut off and spliced into the R and L channel out wires of the Becker harness. I had to fashion a signal ground wire to connect to the white and yellow wires that run to the rear Becker amps. Before I did that, there was no sound.

The dash speakers have been replaced with Blaupunkt unit that have good sound. The rear hat shelf Becker speakers sound tired and I would like to replace them with 6.5" units. Is that the correct size? I had no trouble removing the speaker cover - just pull up at the front edge, then slide forward to remove.

Will I keep it like this forever? Not likely. I will pull new wire someday, I'm just not in the mood to do it now. I sounds good enough for now.
 

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The rear hat shelf Becker speakers sound tired and I would like to replace them with 6.5" units. Is that the correct size?
The Becker speakers on the rear shelf are actually 16 cm, or about 6.3", but most 6.5" speakers will fit.
 
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