Alright, we are getting there.

Fortunately, the meter allows calibration of single ranges of single functions.

Manual asks for R19 series resistors for calibration (probably because suggested calibrator gives these values)

But you can enter your own calibration point easily, so after letting both meters warm up for 3 hours, I carefully measured a range of R20 series 1% resistors using the K196 and proper 4-wire hookup in the low ranges.

Did the 300 ohm, 3K, 30K, 300K and 3M ranges using 200 ohm, 2K, 20K, 200K and 2M respectively.

Now for the good news :

1. My original problem, jumpiness of readings is SOLVED.

The meter now converges reasonably quickly to a stable reading on all ranges.

2. The 300, 3K, 30K ranges are working fine across their full scale. 30M and 300M were already good, I did not touch them.

The bad news is the 300K and 3M are only good at the calibration point (200K and 2M).

Their error factor is not linear, but makes a nice curve whose amplitude is higher for the 3M range.

Some raw data :

K199 measurements on 300K range :

`ohms K196 K199 factor`

200 200.1315 000.357 K 1.784

2 K 1.995296 K 003.538 K 1.773

20 K 20.10081 K 033.272 K 1.655

51 K 50.5125 K 075.213 K 1.489

200 K 198.7545 K 198.756 K 1

300 K 299.9202 K 244.916 K 0.8166K199 measurements on 3M range :

`ohms K196 K199 factor`

200 200.1315 0.00179 M 8.944

2K 1.995296 K 0.01777 M 8.906

20 K 20.10081 K 0.16720 M 8.318

51 K 50.5125 K 0.37790 M 7.481

200 K 198.7545 K 0.99867 M 5.025

300 K 299.9202 K 1.23055 M 4.103

510 K 0.509145 M 1.51577 M 2.977

1 M 0.994468 M 1.80842 M 1.808

2 M 2.014896 M 2.01504 M 1

3 M 2.959862 M 2.08937 M 0.706

OPEN Overflow 2.26766 M K199 measurements on 30K range :

`200 ohm : 00.2001 K `

2 K : 01.9954 K

20 K : 20.1015 KSo there is something common to these 2 ranges but unused by the lower and upper ranges that is still broken.

I will get to enjoy another disassembly it seems

What those 2 ranges have in common is the use of R17B, which is controlled by Q13. I don't really know what to look for however.