U1

[Nu-tra]

I set the voltage to +16 when my ground pin on my DMM is on pin 4 and positive tip on pin 3 when i go to pin 5 i adjust it to -16 and it fluctuates
to -15.4 to -16.5 it's pretty random... is this normal?

[tpryan]

it fluctuates -15.4 to -16.5 it's pretty random

Is this a typo? If it's -16.4 to -16.5 I wouldn't worry about it, though you should be able to adjust it to -16V exactly. If it's jumping between -15.4 to -16.5, something is wrong with the negative supply.

[Nu-tra]

I will set the voltage and it's fine then check the other things then come back to it and it has changed... My +16 is solid... From the previous bulletin I posted "I did replace the C4 capacitor... Which one is the negative supply on the board? Sorry... Once I get one done the rest will be without questions..


V

[tpryan]

U3 and its associated components comprise the negative regulator. C4 and C5 are tantalum bypass capacitors that are located as close as possible to the op-amp. It sounds like replacing C4 solved one problem, but U3 may be faulty as well. I'd try replacing U3, it's a common part you should be able to get locally.