Section {V. MAINTENANCE OF THE ELECTRONIC VOLTMETER ME-202(*)/U

TM 11-6625 -537-14-1

Figure 6-12. Ac range switch printed circuit board, showing component location.

Section {V. MAINTENANCE OF THE ELECTRONIC VOLTMETER ME-202(*)/U

RANGE

...500

6-8 l Fault Indication

NULL

.VTVM

The precision voltage divider is considered to be

AC-de

polarity

(positive)

faulty when differential voltage measurements

Voltage readout dials . . . . . . . . . . ..499.9 1 0

, , , ON (up position)

ON.

are out of tolerance on any range when the voltage

readout dials are set to any position other than 49

e. Allow at least 10 minutes warmup. Hold

99 1 0

switch

OPERATE-CALIBRATE

6-9. Equipment Required for Fault Isolation

C A L I B R A T E and adjust CALIBRATE control

to null VOLTS meter.

Fault isolation of the precision divider consists of

f. Measure the voltage across each resistor on

t a k i n g voltage readings across the resistors

within the divider. Use another electronic volt-

t h e precision voltage divider printed circuit

board. See figure 6-9 for component location. A

meter to make the measurements listed in table 6-

faulty resistor is indicated if the voltage across

the resistor exceeds the maximum voltage dif-

6-10. Test Procedure

ference specified in table 6-2.

a. Remove two screws at the rear and slide the

6-11. General Parts Replacement Techniques

voltmeter from its case.

All parts of Electronic Voltmeter ME-202(*)/U

b. Remove four screws and separate the front

can be reached and replaced without special

panel from the chassis. Gently lay the front panel

procedures. Do not attempt to replace any of the

face down in front of the chassis.

precision w i r e w o u n d resistors with ordinary

CAUTION

power resistors, Nichrome resistors, carbon or

T h e card resistors on the precision

deposited carbon resistors, or metal film

voltage divider printed circuit board can

resistors. Use only approved components when

be damaged by- touching the resistance

making repairs, After replacing components on

wire.

the printed circuit boards, coat any uncoated

c. Remove the cover from the precision voltage

areas around R305 through R31O on the reference

divider printed circuit board.

range resistor printed circuit board, and around

d. Set controls as follows:

6-17