Definitely puzzled here...
For a W126, is it similar to a W123 where I need a new rubber gasket too?
Google and searching around has conflicting answers and I rather know before buying a new windshield from Seattle.
Any help is greatly appreciated!
Hello friends!
Today I have a guide to share!
I have successfully revived a Becker Grand Prix 754 - Serial Number 6725525.
I want to document this before I forget.
As we all know, the security harness screws a lot of people over when removing their radios for behind dash maintenance.
So if you forgot and your radio dumped its RAM, this guide is for you.
Please be advised... This is not for the faint of heart.
You will need:
Solder
A Soldering Iron
A 3.6v replacement battery with solder leads
A DIP8 chip clip
Jumper Cables
A variable bench power supply
A programmer
An AI chatbot of your choice. (Optional... just helped me calculate the serial values in hex.)
This hex block below can be saved and modified by an AI. Just give it this, tell it you're reflashing a Becker 754 RAM module, and tell it you want to use <your serial number here>.
[Original Factory Hex Dump (Serial #6729669)]
Addr: Data
0000: A4 AA C2 3C C0 12 10 AF 48 48 05 E0 8C 11 00 7A
0010: 2E 52 02 21 2C 12 18 20 11 14 5A 0C 88 9C 4F B8
0020: 38 10 03 00 21 0C A2 00 40 05 20 5C 51 89 AC 43
0030: 00 50 04 5C 51 34 20 1A A2 92 12 C0 80 81 48 42
0040: 4D A4 4A 1B 80 A8 13 EC 27 65 DD 20 80 02 01 28
0050: 22 01 5B 70 BB 84 18 28 B4 91 F0 04 0E 75 A3 50
0060: 42 4C 50 13 01 10 60 16 D0 3D B0 21 80 05 86 01
0070: 10 50 A2 D4 03 14 1D 56 43 3E 00 45 00 20 01 50
[Mathematical Re-encoding for Target Serial #3725525]
The Becker architecture stores the indexing word for the unique serial profile suffix at Row 0000, Columns +1 and +2 as a 16-bit Big-Endian word.
* Original Words: AA C2 -> 0xAACC = 43,724 (Decimal)
* Suffix Formula: Core Offset + RAM Word = Serial Suffix
* Isolated Core Offset: 6,729,669 - 43,724 = 6,685,945
* Target Underflow Calculation: 3,725,525 - 6,685,945 = -2,960,420
* Two's Complement Remainder (Modulo 65,536): 0xCCDC
* Modified Bytes: Column +1 becomes CC; Column +2 becomes DC.
[Modified Target Hex Dump (Serial #3725525)]
Addr: Data
0000: A4 CC DC 3C C0 12 10 AF 48 48 05 E0 8C 11 00 7A
0010: 2E 52 02 21 2C 12 18 20 11 14 5A 0C 88 9C 4F B8
0020: 38 10 03 00 21 0C A2 00 40 05 20 5C 51 89 AC 43
0030: 00 50 04 5C 51 34 20 1A A2 92 12 C0 80 81 48 42
0040: 4D A4 4A 1B 80 A8 13 EC 27 65 DD 20 80 02 01 28
0050: 22 01 5B 70 BB 84 18 28 B4 91 F0 04 0E 75 A3 50
0060: 42 4C 50 13 01 10 60 16 D0 3D B0 21 80 05 86 01
0070: 10 50 A2 D4 03 14 1D 56 43 3E 00 45 00 20 01 50
[Power Requirements]
* Voltage: Regulated 12.0V to 13.8V DC supply.
* Current Rating: Minimum 2 to 3 Amps required.
- Idle/Wakeup state draws roughly 200mA - 500mA.
- Driving audio speaker loads pushes current requirements up to 1.5A - 2.5A.
* Safety: Install a standard 5A inline fuse on the positive rail to protect old-school trace geometries.
[Chassis Pin Connections (Without Factory Wire Harness)]
* Switched +12V (Ignition): Feed to the individual recessed round female bullet receptacle hole located on the back panel plate next to the primary fuse capsule.
* Constant +12V (Memory Rail): Feed to the separate individual flat male spade terminal projecting out of the rear frame (stamped with a '+' symbol).
* Ground (GND / Negative): Connect the power supply ground clamp directly to an unpainted part of the solid outer steel casing frame or to the threaded copper grounding lug on the back.
* Note: Avoid the 5-pin inline anti-theft block to prevent microprocessor short-circuit faults.
I also referenced this youtube video I found. Got VERY lucky!
https://www.youtube.com/watch?v=J0fxASPGSw8
Take the above board and some jumpers. Wire them according to the following diagram below:
Pinout diagram. Ignore other components.
Your board, once disassembled, will orient the chip upside down versus this diagram. Please keep that in mind!
BEFORE PROCEEDING: SET YOUR POWER SUPPLY TO 5V 0.300 AMPS. Turn it back off.
Once the chip is hooked up, plug your power supply into the boards VVD for positive, and GND for negative. Make sure that jumper board is connected to the programmer with pin 1 of the board in the closest slot to the latch lever.
Flip your power supply on and plug in the programmer.
Use the settings in the left menu.
You should see Connected or File in the bottom left.
For my radio, the below is the hex I flashed.
A4 9A 9C 3C C0 12 10 AF 48 48 05 E0 8C 11 00 7A
2E 52 02 21 2C 12 18 20 11 14 5A 0C 88 9C 4F B8
38 10 03 00 21 0C A2 00 40 05 20 5C 51 89 AC 43
00 50 04 5C 51 34 20 1A A2 92 12 C0 80 81 48 42
4D A4 4A 1B 80 A8 13 EC 27 65 DD 20 80 02 01 28
22 01 5B 70 BB 84 18 28 B4 91 F0 04 0E 75 A3 50
42 4C 50 13 01 10 60 16 D0 3D B0 21 80 05 86 01
10 50 A2 D4 03 14 1D 56 43 3E 00 45 00 20 01 50
Ask Gemini or ChatGPT to modify it for your serial if you really want. Totally optional.
Copy and paste that hex. Ensure you have Hex text checked. Click ok.
Then validate all your wires and leads, click write.
(I did this like 4 times to validate it worked.)
Wait about a minute.
Click read.
As long as you get the same hex you put in when you wrote, you are golden!
Disconnect all leads and power down. Close and screw back in the top circuit board.
On the rear of the becker, hook up your power supply positive like so and se for 12v, 2.5Amps
The blade is for the power antenna signal.
You will need to jump pins 4 and 2.
DO NOT TOUCH THE 5 PIN CONNECTOR! You risk wiping your RAM and starting over with the Dashes of Doom.
I was able to hyper extend my alligator clip to bite both 4 and 2. Take your negative clip and attach to the screw below the 4 pin socket.
Power on your PSU and click the on button on your radio.
If successful, you will see 87.5 FM on the screen and have no presets in RAM.
Thanks to rick601a and Becker's ridiculous reset pricing for inspiring me to try this on my own.
Happy Restoring!
