This is a follow up to my post:
Trying for sound in a W140. Putting all my gathered info into 1 post...

1992-1993 Bose Beta II System

After a few days of reading and many thanks to the help of James at MBCluster.com I have been able to get my sound system working with a stock Bose Beta II Amp and the Aftermarket Deck. The sound is clear, deep, and overall amazing.

What I had to work with, done by PO:
-An aftermarket deck JVC-R900 was wired from its amplified channels directly to the front door speakers only.
-An antenna extension coax cable was already ran from the Antenna Mast to Deck.
-An antenna ON cable was already ran and wired to the Antenna Mast. (This vehicle does not have the Antenna in the Rear Bumper, will discuss at the end)
-4 Channel RCA cable was already ran from the Deck to Trunk.
-2 Channel speaker wire was already ran from the Deck to Trunk. (These 2 speaker wires were used with wire tees to connect the amplified channels on Deck to the wires at the stock Amp, thus bypassing the stock Amp and running the sound directly to the speakers in the front door)
-No Bose Beta II Amp present
-No Antenna Tuner present
-Data cable butchered (From stock Deck to stock Antenna Tuner)
-Cut ends on Antenna Tuner output cable (which connects to the stock Amp)

What I needed:
-Stock working Bose Beta II Amp
-Patience while rewiring & soldering

1.
I removed the wire tees from the cable in the trunk that should connect to the stock Bose Amp. Instead, there was no stock Bose Amp.

2.
The wire tees damaged the stock wires, so I peeled back the insulation, soldered the wires to add strength back to them, covered the solder in liquid tape, and finally electrical tape. (Pics 1-4)

3.
I used 2 of the existing 4 channel RCA cables and converted them to Speaker wire outputs so that I could solder them directly into the stock Bose Amp input wires which ran from the stock Antenna Tuner. Since the stock Bose Beta II Amp is only a 2 channel Amp, the other 2 RCA's were not required. (Pic 5)

4.
I soldered the now converted Speaker wires to the already cut stock output wires that run from the stock Antenna Tuner to the stock Bose Amp input wires. (Pic 6)
Right Channel:
Red +
Blue -
Left Channel:
White +
Yellow -

5.
The stock Bose Beta II Amp also requires a Amp ON signal, so I used the existing butchered Data Cable and used the RED & YELLOW wires inside it as my signal wire for the Amp ON. I used both wires and soldered their ends together as these were very flimsy and I wanted a thicker connection. A total of 6 wires were inside this Data Cable. (Pic 7)

Pic 8 shows the finished work.
Pic 9 shows the work in progress.

You can see I used the space where the stock Antenna Tuner was to organize and tie wrap my wires. The 2 Channels of the RCA were connected to the FRONT RCA pre-amp outputs on my Deck and the 2 other unused RCA Channels were connected to the SUB RCA pre-amp outputs. As you can see I shrink wrapped those unused RCA ends as they may be used in the future for adding subs without having to pull the Deck out.

Antenna Mast:
I've read on some posts that the FM Antenna is in the Rear Bumper & AM Antenna is in the Rear Glass. I could not find any evidence of that and am starting to think this was only true for the W140's with the telephone option. This vehicle does/did not have the telephone, thus the Antenna Mast is used for the Radio.

Pic 10 shows the Antenna Mast and the connections with the spot for the telephone empty.

Pic 11 is the driver’s side behind the rear wheel where the wire for the Antenna should be running through if indeed it had the antenna built into the rear bumper. It does not.

I hope this helps other people achieve a solid factory sounding system. This sound is amazing especially for 1992-1993 and IMO can't compete without 1000's of $ in upgrades.

Any questions, please feel free to ask.

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Pics 6-9

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Pics 10-11

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