prodigit 3320.Need repair or calibration. Need a scheme.

[Alex06]

Hello. This is still a newcomer. I decided to ask you for help, as I myself couldn’t do anything yet.
I have an electronic load Akip-1301A 60V / 30A
 (foreign analog of Prodigit 3320 60V / 30A) copy of 100%.
The malfunction lies in the inaccuracy of the readings that I submit to her voltmeter.
From 0 to 19 V is not resp., But from 20 to 60 V goes.
There are several tuning resistors, but so far they do not help.
On the Internet I was looking for a service manual or circuit, I did not find anything.
Maybe someone will help with the scheme or tell me where to go next.

[wraper]

Пост на всём кроме английского могут удалить, так что советую писать на нём. Тем более что большинство местного народа не будет заморачиваться переводить. И это не копия, а он и есть. Весь акип это тупо смена шильдика.

[dom0]

The auto-ranging of the meter may be broken.

[Alex06]

One person suggested that it should be calibrated for accuracy. In the service manual it is. But on the Internet, I did not find it.

[wraper]

From 0 to 19 V is not resp., But from 20 to 60 V goes.

Do you mean up to 19V it does not work at all or you cannot adjust? If inaccuracy, how much. It could be a fault, not calibration problem.

[Alex06]

measured the reading

[dom0]

So it should be accurate to +- 0.05 % + 2 counts, yours is up to 0.2 V out (15 V / 15.2 V), +1.3 % error.

Range switching is indeed done at 20 V. So the lower range needs adjustment, preferably to an reliable, accurate multimeter. Handheld 4 1/2 digit would probably be ok. There is probably one trimmer or 20-turn pot for each range.

[Alex06]

I twisted some resistance, and put in place. They did not help. Only the general adjustment range was found

[danilnik]

Hello everyone.  Can I bring this topic up?  Maybe someone got a service manual or calibration method for this device?