S e c t i o n IV. ORGANIZATIONAL MAINTENANCE OF ELECTRONIC V O L T M E T E R ME-202( * )/U

TM 11-6625-537-14-1

Table 4-4, Organizational Troubleshooting

Probable cause

Corrective action

Malfunction

Defective lamps, or defective fuse F1.

1. Decimal indicator lamps do not

Replace defective lamp(s) (para 4-

1 la ). If no lamps light, replace

light.

fuse F1.

Check for a slight buzzing sound: if

2. CALIBRATE control has no effect

Defective chopper.

on VOLTS meter needle.

there is no buzzing, chopper must

be replaced by general support

maintenance personnel.

instrument to remove

3. VOLTS meter needle deflects more

Clean

Dirt in circuit board connectors or in

than one-tenth of full scale when

contamination.

switch contacts causing excessive

controls are set as follows:

electrical leakage.

RANGE

500

NULL

Voltage readout dials

49000

4. VOLTS meter needle deviates from

ZERO ADJ control improperly set.

Adjust ZERO ADJ control R227

zero when controls are set as

(para 4-llb ).

follows:

RANGE

NULL

.01

Voltage readout dials

S e c t i o n IV. ORGANIZATIONAL MAINTENANCE OF ELECTRONIC

V O L T M E T E R ME-202( * )/U

4-10. Replacement of Fuse

a. Connect the electronic voltmeter to a 115-

volt source. If the electronic voltmeter is wired for

I f t h e e l e c t r o n i c v o l t m e t e r i s completely

230-volt operation, connect to a 230-volt source.

i n o p e r a t i v e , the fuse is probably defective.

b. Mechanically zero VOLTS meter control

Replace the defective fuse with a new one. If the

with mechanical adjustment screw on meter case.

new fuse blows when power is applied, repair at

c. Set ON switch to ON and allow at least a

higher maintenance level is required. Replace the

20 minute warmup.

fuse as follows:

d. Set controls as follows:

a. Turn the fuseholder cap on the rear panel

(1) RANGE.5.

counterclockwise to unlock the cap.

(2) NULL .01.

b. Pull out the fuseholder cap and the defective

(3) Voltage readout dials 0.

fuse.

e. Adjust ZERO ADJ, R227, for zero VOLTS

c. Remove the defective fuse and replace it

meter deflection. R227 is in the lower right corner

with a new one.

of the printed circuit board on the left side of the

4.11. VOLTS Meter Zero Adjustment

cabinet when facing the front panel and is ac-

The electrical zero of the VOLTS meter may

c e s s i b l e through the ventilation holes in the

require

adjustment as indicated by the

cabinet. Use an insulated screwdriver to prevent

troubleshooting tables, or when changing from

accidental shorting to ground.

60-Hz to 400-Hz input power, Proceed as follows:

4-4