[REPAIR] Multimiter sanwa PC510a strange temperature reading

[ss45]

Hi I have sanwa PC510a multi.
the temp reading is offset by about -1000 C
it was fine few months ago and started acting up recently
so room temp will read ~970 C

it is not the sensor ( K type) as when I plug to other meter (fluke) it reads just fine
the sensor is sanwa original

all other readings like voltage AC&DC, current AC&DC, resistance, diode, and capacitance give normal readings within
meter's specification.

I ve tried searching internet for schematic, but no luck so far.
I guess it has sth to do with the cold junction compensation circuit or sth else, but i am really blind about servicing meter.

i ve tried cleaning and brushing pcb with alcohol, again no change.

any help is appreciated.
thanks

[Per Hansson]

There is a thermistor inside the meter, probably it is open circuit with a reading like that...

[stj]

usually,
although some chips just have a programamble value in them that assumes 20' ambient.

[ss45]

@per Hansson
Yeah it is probable. But the big question is which one

Heres link to some of the photos
link

@stj
I wonder if only we could reprogram that chip....
Maybe as the chip becomes older values stored inside it become corrupted. Or in a very unlikely event, stray radiation knocked a bit off of a cell, resulting in error'... Hmmm......

[stj]

those meters give "err" on the display if they get corrupted