Lifted the 24C02 EEPROM's SDA, SCL pins and attached wires. Used an Arduino and 3V level translator.
Bytes match a Russian AN8008 dump, aside from the CAL factors.
The DMM IC is full featured but the multimeter's hardware (rotary switch, die-bonding PCB) prevents their use. LCD has all annunciators though. I don't have the exact datasheet for the DMM IC, just its predecessors.
RS-232 output - I can't see the IC TXD pin bonded.
hFE test - needs transistor socket and 3 resistors but could be done from the front banana jacks.
Mid-range amps - not possible as rotary switch does not bypass 99R (uA) shunt. I still hear Dave yelling about this gyp. Could add a switch, lol.
Temperature - I enabled in EEPROM on the mV function, works °C/°F and factory CJC CAL is already set at 25°C fixed.
NCV - could be used with antenna 10MEG resistor added.
Clamp-on CT - could add if you enter CAL factors.
Presently only two buttons: SEL/HOLD and RANGE/BL.
To add MAX/MIN & RELATIVE buttons- I haven't checked if that MCU pin available; they are muxed.
So you can enable the temp function (although
shown here it's advertised in Russia; my meter did not have the function).
Also you can change timer settings for BL and power off etc. or change calibration.
Factory alarms set to 1,000VDC and 750VAC. OL at 1,100VDC and 800VAC.
It was a fun adventure.