Unilab voltage offset and current limit trimmers

[pstemari]

These appear to be off. With them turned to the limit, the "zero" output voltage is -0.015 volts and the current limit can only be brough down to 3.1 amps.

Looks like this is to be expected since the 337 controlling the negative rail can only go down to 1.25 +/- 0.05 volts and the switcher's control voltage is 1.23 +/- 0.05. The circuit needs a series resistor inline with the voltage control pot P1 to get around this.

Setting the current limit has a similar problem, but in that case the existing R11 can be replaced with a 180K resistor to cure the problem.