I posted thermal photos before :
You can see them all
in my K2001 repository.
Usually if someone buy old 2001, I would do next:
1. Take boards of meter, take photos (try not to use flash, to avoid glare on PCB
)
2.
Upload photos for my collection
3. Replace all thruhole electrolytic caps. You will need 470uF x 63V 2pcs, 2200uF x 35V big ones, 1000uF 50V x 3pcs, 2200uF x 16V - 1pc, 1000uF 35V x 3pcs (for digital board), 47uF x 63V for digital board.
4. If there is electolyte gunk from old caps - you must desolder stuff around affected area, clean area very well, solder parts back. Believe me, this will save you DAYS of troubleshooting...
5. If any traces damaged/black - repair them. Pay attention to little vias around, to make sure they are not eaten/open.
6. Assembly stuff back, power on, check voltages (5V digital, 5V analog, +15V, -15V, +8VF, -8VF (there are test pads near A/D board connector), +38V, -38V (test pads near AD637)).
6b. Replace fan, usually they are bad in all old units (You need 40x40mm 12V 0.1A DC Fan).
7. CR11x avalance diodes near transformer must be cold, if they heating up - something around them and caps is messed up.
8. If all voltages within few % tolerance, run self-test and report what errors occur
9. Dump firmware and 24C16 calibration ROM contents, upload them for our collection
304.6,304.7 errors on ohms are usually contamination/dirt around ohm source ranges (Area around U325). If lower 304.x errors present - check Q320,Q311,Q312.
Correct voltage reference on pin 1 of A/D connector is -10.xx VDC.