Another DMM turned up, a French re-badge of a BM817 sold cheapish as "untested".
On arrival the 1A fuse for the mA input was missing, other than that flickery LCD segments due to the LCD/zebra strip assembly slightly unscrewed.
Once the fuse replaced a quick check shows DCA to be good, even on mA range, was not able to test below 10mA with my lab supply though.
A quick
![Ohms \$\Omega\$](https://www.eevblog.com/forum/Smileys/default/omega.gif)
test continuity and short work well, 190k test resistor also spot-on, will have to check some intermediate values.
DCV is within spec also except for the 5V range that is totally off.
The reading on 5V DC range is stable but displays only half the input voltage.
Measuring a 0.5V input will read 0.253V, displaying anything more than 0.301V (0.6V input) will display as an overload.
The meter uses an AD-85-4 ADC, as mentioned by others here it seems identical to the Fortune FS970X.
Where to look first? I made some quick in-circuit measurements at the resistor network on pins 18 to 22, all seems fine.
Is there a known way to get into calibration mode? I have an I.R. interface if that's needed.