MODEL 6259B
6260B
62610
6268B
6269B

is equal in either direction (within 25%). To check for imbalance, proceed as follows:

a.Connect appropriate Ioad resistance across rear output terminals of supply as follows:

Load Resistance 0.2 Ω 500W, ±5% O.1 Ω, 1000W, ±5% 0.4 Ω, 1000W, ±5% 1.33 Ω, 1200W, ±5% 0.8 Ω, 2000W, ±5%

b. Connect variable auto transformer between input power source and power supply power input; adjust auto transformer for 230Vac input to supply.

c. Connect oscilloscope (ac coupled) between TP102 and TP103 (across series regulator).

d. Turn CURRENT controls fully clockwise, turn on supply, and adjust VOLTAGE controls for maximum rated output voltage.

e. Adjust oscilloscope to observe 120Hz sawtooth waveform. Peak amplitudes of adjacent sawtooth peaks should be within 25% of each other.

f. If amplitude difference is greater than 25%, turn off supply and replace R82 with decade resistance.

9.Turn on supply and adjust decade resist- ance to reduce imbalance to within 25%.

h. Vary input line voltage from 207 to 253V ac and insure that imbalance does not exist any- where within this range. Replace decade box with equivalent resistor.

NOTE

If imbalance cannot be reduced to within 25%, check capacitors C70 and C72, and diodes CR79 through CR84. If these components test satisfactori- ly, the problem may be due to distortion present on the ac power line.

5-103PREREGULATOR TRACKING (50 and 60Hz Operation)

5-104 To adjust the voltage drop across the series regulator, proceed as follows:

a. Connect appropriate load resistance across rear output terminals of supply as follows:

Model

Load Resistance

62S9B

0.2 Ω

500W,

±5%

6260B

0.1 Ω, 1000W,

±5%

6261B

0.4 Ω,

1000W, ±5%

6268B

1.33 Ω, 1200W, ±5%

6269B

0.8 Ω,

2000W, ±5%

b. Connect variable auto transformer between input power source and power supply power input adjust auto transformer for 230Vac input to supply.

TM 11-6625-2958-14&P

Connect dc voltmeter acress series regulator (TP102 and TP103).

d. Turn CURRENT controls fully clockwise. e, To check voltage drop across regulator

at low output voltage, short circuit load resistor and adjust VOLTAGE controls for maximum rated output current on front pane 1 ammeter.

f. Adjust R70 until voltmeter reads 3.5±

0.3Vdc.

g. To check the voltage drop at high output voltage, remove short circuit from acress load resistor and adjust VOLTAGE controls for maximum rated output current. Voltmeter reading should again be 3.5 ± 0.3Vdc.

h. Vary input line voltage from 207 to 253V ac. Voltmeter reading should vary between 3.2 (minimum) and 3.8 (maximum) volts. If reading exceeds this range, proceed with Step (i).

i . Replace resistor R77 with decade resistance box. Vary input line voltage between 207 and 253Vac while adjusting decade box until voltmeter reading variation is minimal and within range of 3.2 to 3.8Vdc. Rep lace decade box with equivalent resistor.

5-10550Hz OPERATION (Option 005)

5-106 If the supply is to be operated from a 50Hz ac input, the following modifications are required:

a. Replace resistor R82 with 240 Ω, ±5%, 1/2 watt resistor, and check ripple imbalance as described in Steps (a) through (e) of Paragraph 5-101.

b. Perform preregulator tracking adjustment described in Paragraph 5-103.

5-107CROWBAR TRIP VOLTAGE

5-108 To adjust A5R125 (OVERVOLTAGE ADJUST), proceed as follows:

. Turn screwdriver adjustment, A5R125, fully clockwise.

b. Turn on supply.

c. Set voltage output to desired trip voltage. d. Turn A5R125 slowly counterclockwise

until the crowbar is tripped (meter falls to zero volts).

e.Turn off supply and turn down output

voltage.

f.Turn on supply and set desired operating output voltage.

NOTE

It is recommended that the crowbar be set to no less than 5% of the desired output voltage plus two volts, in order to avoid false tripping of the crowbar. However, if occasional crowbar tripping on unloading can be tolerated, the crowbar trip point can