CONVERSION FOR DIFFERENT INPUT VOLTAGE .

4.5.3 CONVERSION FOR DIFFERENT INPUT VOLTAGE .

To convert from one line-voltage input to another, remove the

jumpers which interconnect the transformer windings. These jumpers

are located on the etched board. Connect the proper jumpers as noted on

the schematic diagram (see Figure 4-7). Terminals AT1 and AT4 are

those located nearest to the fuse. See Figure 4-2. The numbers are silk-

screened on the reverse side of the board. Insert a proper value fuse.

If the input voltage is changed, the plate on the panel, just above

the power cord, should either be removed or marked to indicate the

remount the plate

correct power input required. Recommendation:

with the reverse side up and print new input requirements with an in-

delible marking device.

4.5.4 NO FLASH NO DIAL LIGHT.

If the strobotron tube will not flash and the RPM dial is not ill-

uminated; unplug the instrument, remove it from the case, and:

a. Check for open fuse. If fuse blows when replaced, refer to

b. Flip power switch on and check for continuity between pins

of power-cord plug. If continuity check indicates an open circuit, check

power switch and continuity of the power input circuit.

It is possible that the pilot lamp is defective and there is also

some other difficulty preventing the strobotron from flashing. Refer

4.5.5 INSTRUMENT BLOWS FUSES.

If the stroboscope continually blows fuses (see Figures 4-1, 4-2,

and 4-7):

a. Make certain replacement fuse is correct value.

b. Make certain transformer is properly connected.

c. Check for accidental short circuits to ground at secondary of

power transformer (AT5), or +400-volt (AT17) and -400-volt (AT20)

lines.

d. Check for possible short circuits across C12C or C13.

e. Check for low back resistance of rectifier diodes CR1, CR2,

CR3, and CR4. Measure forward and back resistance of each diode.

(Measured values will depend upon type of instrument and scale used.)

The back resistance should be much greater 100 times greater, for

example than the forward resistance. (The +400- or -400-volt supply

will probably be low if diodes are faulty).

4.5.6 NO DIAL ILLUMINATION.

If the indicator

under the RPM dial is not illuminated, but the

strobotron lamp fires,

pilot lamp (P1, Figure 4-1) is defective. To re-

place, swing back the

etched board (refer to paragraph 4.4.6) and unclip

the lamp socket from

its bracket. The lamp can now be easily replaced.