Adjustment and Calibration

Current Limit Adjustment

+6V Supply. To adjust the current limit circuit in the +6V sup- ply, proceed as follows:

a.Check the setting of the current limit by performing steps

(p) and (q) on page A-5. (Be sure to set the output voltage to 6 volts.) If reducing the load resistance permits the cur- rent to exceed 2.9 A, stop, turn R6 slightly clockwise, and repeat the test. If, instead, the current begins to fall before it reaches 2.6 A, turn R6 slightly counter clockwise and repeat the test.

b.Recheck the setting and readjust R6 until the test shows that the current limit circuit begins to reduce the current when a decreasing load resistance increases it to 2.75 A

± 5%.

Meter Calibration

Panel Voltmeters. To calibrate voltmeter, proceed as follows:

a.Connect DVM across +20V output terminal and COM ter- minal of the supply.

b.Turn on the supply.

c.Set the output voltage below 18V (ex, 15V), and adjust R11 on the display board until front panel VOLTS display reads exactly DVM value. Next, set the output voltage above 20V (ex, 21V) and adjust R17 on the display board until front panel VOLTS display reads exactly DVM value.

No other voltage output needs to be calibrated after calibrating the voltmeter of +20V output.

Panel Ammeter. To calibrate ammeter for +20V output and -

20V output, proceed as follows:

a.Connect RS between +20V output terminal and COM ter- minal and connect DVM across RS.

b.Push +20V meter switch and turn ±20V VOLTAGE control fully clockwise.

c.Turn on the supply and adjust R5 on the display board until front panel AMPS display reads exactly DVM value divided by Rs.

d.To calibrate the ammeter for +6V output, select +6V meter switch and turn +6V VOLTAGE control fully clock- wise.

e.Adjust R61 on the main board until front panel AMPS dis- play reads exactly DVM value divided by Rs.

A-11