Will a Becker 780 fit where a 753 goes? - PeachParts Mercedes-Benz Forum

waybomb · #1 08-09-2007, 09:04 PM

I have a dead radio in my 1987 420SEL. It smells a little smoked.

I went to the Car Audio section here with little help, so I am hoping someone here can help.

I went to the Becker site. The 754 which I have fits a 1986 and 1987 126. There are a number of 780 Beckers on Ebay. The 780 fits 1988 and 1989 126 cars.

Will a 780 be a direct replacement for a 754? Anybody ever done that? Or, does somebody have a working 754 for sale?

MB-Dude · #2 08-09-2007, 09:54 PM

Yes, the Becker 780 can be a direct replacement for the Becker 754. Literally days ago, I was experimenting with both the Becker 754 and Becker 780 in my '79 240D. As far as sound is concerned, the two units are interchangeable. There are slight variation in the controls, but the units are pin-for-pin interchangeable. However...

If you have a power antenna, I do not believe the Becker 754 is designed to control it. If you have a manual antenna, then either will work.

As it turned out, I installed the Becker 754 in my '79 as it is the closest in vintage and I have a manual antenna.

waybomb · #3 08-09-2007, 10:03 PM

When I turn my 754 radio on, well, when it worked, the antenna went up. Looking at the pix on ebay auctions, the pin-outs seem the same. If I can find one cheap enough, I'll give it a try.

MB-Dude · #4 08-09-2007, 10:11 PM

If that's the case, then you *must* look for a Becker 754 or a Becker 780 that has a small box attached to the rear of the unit. It should have a 3-pin connector to it, which feeds power, etc. to the power antenna. If you need pin-outs, let me know. But the box hanging off the back is very distinctive. I can send a picture, if you need it.

waybomb · #5 08-09-2007, 10:32 PM

My 754 does not have a black box on the back. The back of my 754 looks like the one in this auction except on my 754, the little white plug near the antenna lead on the 780 is non-existant, and the 754 I have has a recessed antenna connection instead of the external cable as shown in the 780 auction. The power, speaker, ground, and antenna connections are the same in both.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=013&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=230159166996&rd=1

MB-Dude · #6 08-09-2007, 10:44 PM

Hmmmm.... It's possible your car system has an additional power amplifier, separate from the radio, that controls your power antenna and front/rear speakers. Question for you - How many cables connect to the rear of your existing unit?

For the Becker 754 and Becker 780 to be completely interchangeable, there can be only 4 cables:
1x Antenna cable
1x 4-Connector cable (red, gray, black, brown wires)
2x Speaker cables

The antenna connection outside the box is not a problem. The small box I refer to is very distinctive and sticks out like a sore thumb, but may be a part of a separate unit in your vehicle.

Bottom line - If your unit looks like the rear of the unit in the E-Bay picture and your unit only has the 4 cables above, they should be interchangeable.

One more thought - There may be yet a fifth wire - a brown wire - that connects to a single spade lug on the radio chassis. This may or may not exist in your setup, but does not effect Becker 754 and Becker 780 interchangability.

waybomb · #7 08-09-2007, 10:48 PM

Any idea what the small white connector is for in the ebay picture? Mine does not have that connector.

MB-Dude · #8 08-09-2007, 10:50 PM

Quote:

Originally Posted by waybomb

Any idea what the small white connector is for in the ebay picture? Mine does not have that connector.

No clue. If I had to hazard a guess, I would say it was some sort of test connection. The fact that its white in color suggests it to be non-standard. But again, I have never seen anything like it.

MB-Dude · #9 08-10-2007, 10:56 PM

Quote:

Originally Posted by waybomb

Any idea what the small white connector is for in the ebay picture? Mine does not have that connector.

Curiosity got the best of me and I dissected my Becker 780 in search of this white connector. Lo and behold, I found it.

Referring to the attached pics, the first picture shows the power antenna control box I referred to in previous posts. You can also see that there are 3-wires that feed power/signals to the power antenna. The main 4-connector cable is also visible.

Picture #2 shows a bit better detail of the 2 connectors.

Picture #3 illustrates that there is only one Phillips screw holding the power antenna control box onto the head unit.

Picture #4 clearly shows the power antenna box removed and the white connector. This white connector feeds signals to the power antenna control box that is attached to the rear of the radio.

If you have a manual antenna, then this unit is interchangeable with a Becker 754. The power antenna control box is superfluous and not used/needed.

If you have a power antenna and a 3-wire power antenna cable, then a Becker 780 unit must have the power antenna control box attached.

If you have a power antenna but do not have a 3-wire power antenna cable, then your power antenna is controlled by a separate unit. In this case, the Becker 754 and Becker 780 are interchangeable. The power antenna control box is superfluous and not used/needed.