Trimble 4000SX Deep Dive

ROM Images

ROM Label Board Marks File
U36U-36 Rev 3.30
4000
Chk Sum 52EA
ROM0-UU36.rom
U37U-37 Rev 3.30
4000
Chk Sum 2500
ROM9-UU37.rom
U38U-38 Rev 3.30
4000
Chk Sum E240
ROMA-UU38.rom
U44U-44 Rev 3.30
4000
Chk Sum D16B
ROM0-LU44.rom
U45U-45 Rev 3.30
4000
Chk Sum 8E92
ROM9-LU45.rom
U46U-46 Rev 3.30
4000
Chk Sum 0717
ROMA-LU46.rom

Merged ROM Images

Bank File
ROM0 (U36+U44)ROM0.bin
ROM9 (U37+U45)ROM9.bin
ROMA (U38+U46)ROMA.bin

Memory Map

000000 - 003FFF ROM0
004000 - 007FFF RAM
090000 - 09FFFF ROM9
0A0000 - 0AFFFF ROMA

Flight Case Cannon Connector Pinouts

Purpose Connector Pinout
AC Line In Cannon MS3106A14S-7S
A Line
B Neutral
C Ground
DC Power Cannon MS3106A10SL-4S
A Positive
B Negative
RS232C Cannon MS3106A14S-5S
A Signal Ground
B Transmit Data
C Receive Data
D CTS
E DTR

Firmware Teardown

Unlike later receiver models like the 4000ST, The majority of the firmware running on the 4000SX runs inside a stack based virtual machine. I have reverse engineered most of the Instruction set. I have also created a disassembler for the virtual machine code contained in the ROMS.

Disassembly at my current level of knowledge: disassembly.txt

PCB Photos

10670 - DAC

Component side

Copper side

10850 - Synthesizer

Notes

On the board shown, Tantalum capacitor C24 had shorted, as they do, which shorted the output of regulator U10. This caused L7 and L8, the two inductors in series on the input of U10, to overheat, which is why the board is discoloured in that vicinity. This failure eventually burned out the 1.5A fuse in the power supply protecting the +14V rail. The charred inductors were replaced, as were all tantalum capacitors.

Component side

Copper side

10853 - Mixer/VFO

Component side

Copper side

10924 - Lock Board

Component side

Copper side

Other Stuff

The OCXO is a Piezo Systems 2810007-23, which is a clone of the HP 10811B.

Mixer/Lock/Synthesizer Module Power Cable

The Mixer (10853), Lock (10924) and Synthesizer modules (10850) are interconnected with a 10 conductor ribbon cable that is used to distribute power among the cards. Pin 1 is closest to the aluminum faceplate of the card, and closest to the J20/J30/J40 end of the card. The pinout:

1  +12V for OCXO (Produced from +14V by U31, an LM317 on lock board)
2  GND for OCXO
3  -12V (Produced from -14V by U11, an LM337 on synthesizer board)
4  GND
5  -14V (provided by system power supply)
6  +12V (Produced from +14V by U10, an LM317 on synthesizer board)
7  GND  (probably)
8  +14V (provided by system power supply)
9  +5V  (provided by system power supply)
10 +5V  (provided by system power supply)

RF Block Diagram

RF Block Diagram