I think you have a fault (or cold solder or something) with your flash, where the firmware is stored.
There are 2 identical flash chips, doing the job in between them: U215 and U117. Treat these 2 as one chip.
These chips have 3 memory banks that we use. This is basically how it works:
1. Basestation stores the last 2 downloads of firmware. These two can be the same firmware, downloaded twice or separate firmwares.
2. Basestation always boots up with the firmware sitting in bank 1. We do not have access to this bank. It gets its contents automatically either from bank-2 or 3.
3. When a firmware is downloaded, it either goes to bank 2 or bank 3
4. Last download location flag is stored in U10 (SRAM) which is battery backed up
5. When unit is re-booted, depending on the last download location, the firmware is automatically transferred from bank 2 or 3 to bank 1 and then the unit boots up (from bank 1).
So, I think there is something wrong with the flash device(s). It looks like the last download does not get transferred to bank-1. It is booting up 1.5.7 because that’s what is residing in bank-1.
Or it may be (unlikely) that the internal battery is flat and the unit does not get the ‘last download position’ flag. In that case, it will always boot up from bank-1. Measure the battery BT1.
Also check if you have V2 residing in bank 2 or 3. If you have, then there is no problem with downloading the firmware mechanism. If not, then the problem might be before the flash (i.e, the firmware may not have reached flash to be stored)
To check bank-2 and 3 firmware:
1. Switch the unit off
2. Press and hold ‘Channel A talk’ button and ‘setup’ encoder while switching the unit on.
3. Beltpack indicator lights (10 LEDs) should all light up
4. Release the talk button and the encoder. 1st beltpack button should stay on, the rest should be off.
5. Rotate the encoder 2 notches so the beltpack LED moves from 1st to 3nd. Press the encoder and the units should bootup from bank-3 (Latest firmware should be there)
6. Do the above (from step 1 to step 5) for bank-2 and find out the firmware revision in that bank
7. If it still boots up with 1.5.7, then it means there is only 1 firmware in the unit and it did not take V2 at all.
How to erase firmware in all locations:
1. Set all 4 switches on dipswitch S1 to OFF.
2. Turn the unit on for 30 secs
3. Turn off the unit and set all S1 to all ON.
4. Reboot unit. It should not boot up. The 5th beltpack indicator light will probably be on (not so sure). Unit will be waiting for a serial firmware download. Use S4 to download V2.
Last resort is to change the flash devices. Change them both.
I hope this helps,
Oguz