TM 11-6625-2958-14&P

Table 5-8. Checks and Adjustments After Replacement of Semiconductor Devices (Continued)

REFERANCE

I

FUNCTION OR CIRCUIT

 

 

 

CHECK

ADJUST

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Limiting

action and level.

- - -

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Output voltage, ripple imbalance, and

R70, R82

 

 

 

 

 

 

preregulator

waveforms.

 

 

 

 

 

 

 

 

 

CR90 thru

 

Crowbar.

 

 

 

Trip voltage, voltage across series regu-

R95,

CR93,

 

 

 

 

 

lator when crowbar is tripped, supply

A5R125

A4CR108,

 

 

 

 

 

stability.

 

 

A4CR110

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A4CR101 thru

 

Main rectifier

diodes.

Voltage

across main filter capacitors.

- - -

A4CR104

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A4CR105

 

Reverse

voltage

protection.

Output

voltage.

- - -

and

 

 

 

 

 

 

 

 

 

 

A4CR106

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VR1

 

Voltage

clamp

circuit.

CC

load regulation.

- - -

 

 

 

 

 

 

 

 

VR40

 

Mixer amplifier

stabiliza-

CV

transient

response.

R47

 

 

tion diode.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+6.2V and -6.2V reference voltages.

- - -

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Trip

voltage.

 

R95,

 

 

 

 

 

 

 

 

 

 

A5R125

 

 

 

 

 

 

 

 

 

 

 

5-73ADJUSTMENT AND CALIBRATION

5-74 Adjustment and calibration may be required after performance testing, troubleshooting, or repair and replacement. Perform only those adjustments that affect the operation of the faulty circuit and no others.

5-75METER ZERO

.5-76 The meter pointer must rest on the zero calibration mark on the meter scale when the instrument is at normal operating temperature, resting in its normal operating position, and turned off. To zero set the meter proceed as follows:

a.Connect load resistor of value shown in Figure 5-2.

b.Turn on instrument and allow it to come up to normal operating temperature (about 30 min- utes).

c.Turn instrument off. Wait one minute for power supply capacitors to discharge completely.

d.Insert sharp pointed object (pen point or awl) into small indentation near top of round black plastic disc located directly below meter face.

e.Rotate plastic disc clockwise until me- ter reads zero, then rotate counterclockwise

slightly in order to free adjustment screw from meter suspension. Pointer should not move during latter part of adjustment.

5-77VOLTMETER CALIBRATION

5-78 To calibrate the voltmeter, proceed as fol- lows:

a.Connect differential voltmeter across supply, observing correct polarity.

b.Turn on supply and adjust VOLTAGE con- trols until differential voltmeter reads exactly the maximum rated output voltage.

c.Adjust R106 until front panel voltmeter also indicates exactly the maximum rated output voltage.

5-79AMMETER CALIBRATION

5-80 To calibrate the ammeter, proceed as fol- lows:

a.Connect test setup shown in Figure 5-8.

b.Turn VOLTAGE controls fully clockwise.

c.Turn on supply and adjust CURRENT con- trols until differential voltmeter reads 0.5Vdc.

d.Adjust R101 until front panel ammeter in- dicates exactly maximum rated output current.