Geodimeter 600 series / Alfa CU backup batteries and board level debugging

Hi to all!

We have been using a Geodimeter 640 robotic with an Alpha CU in research for autonomous vehicles. So we are not surveyors but electrical engineers and computer scientists. We are still amazed by the high precision surveyors and such a device deliver!

We have been using the Geodimeter with an Alfa CU. We had quite good results and love the robotic feature and the simple serial interface. Yesterday I was not able to switch on the device any more. When pressing the PWR button the device beeps and the shutter (?) makes some noise. Quite normal. I am still able to move the device with the servos and aim at a target. So the 'gun' seems to work quite normal. The sound indicating that some signal is reflected still works. But there is nothing on the display and A/M button does nothing (obviously, because the compensator was not initialised).

I removed the CU from the 'gun' and powered it directly. Still, the CU does not display anything.

I tried resetting the device with PWR + CON, but no luck at all.

After some research I found out that the CU has two 3 Volts lithium batteries (CR2430) and the firmware is stored in volatile RAM (SRAM, KM6810000 / KGT1008C2E).

The battery behind the processor (good old TS80C188) still has 3.0 Volts and continues to supply the SRAM. The SRAM has a minimum voltage requirement for data retention of 2.0 Volts (from the datasheet). So I think the firmware is not yet lost.

The second battery (on the bottom left if you look at the display) was dead (a bit swollen and only 0.5 Volts). I tried to supply 3.3 Volts from a new battery at that connection but without results.

We never got any warnings about backup batteries and the device was in service one year ago when we bought it.

I am curious if someone has access to a more detailed description of the device (schematics, ...). I saw some high-quality comments on the Geodimeter internals in that forum. What is the second battery for? It would be great we could understand more about the CU to repair it. The 6-layer board is marked "MAP D" "571 203 140".

What about the firmware? Can anyone provide it?

We are not surveyors but some skilled EE people with lots of experience in circuit board design, embedded software development and debugging.

Looking forward to receiving any kind of input. It would be great if we could revive that nice Geodimeter 640 again.