M625B — Power Supply

M625B POWER_SUPPLY DC Output: +25 volts amperes load currents from Line Regulation: 1% for Iine variations from 105 125 from 210 250 volts ac respectively Load Regulation: for load variations from zero full load. Ripple and Noise: Less than 500 microvolts RMS for all Iine and load conditions specified above Internal Impedance: Less than ohm from dc to 20 kHz _ Stability: 0.1 volts measured over an period, after minutes warmup - hour Protection: Overcurrent and short circuit foldback_ Overvoltage crowbar.

AC Input: 115/230 volts ac nominal 50/60 Hz . Maximum input power: 525 VA_ Ambient Temperature: Dimensions: 40 degrees Celsius at rated output_ 8.45" wide 5.1" high 13.7" deep (214.6 mm 130 Mm 348 mm) Accessories: MF6A mounting frame (accommodates two M6258 power supplies) _ 1-1

M625B POWER SUPPLY 10) ~Apply power and check both output voltages_ If the regulator is opera ting correctly, the +25 and the -25 outputs should be within approximately volts of specified output. Adjust R14 (1-117) to raise or lower the +25 V output. Adjust R18 (1-117) to equalize the differential between the two voltages_ As it is important that the two voltages be identical, use DMM to check both voltages 11 ) ~Set the metering switch on the front panel to OFFSET and plug the DMM into the meter jacks.

~Adjust the calibration control R28 (1-117) to read volts at the DMM _ 12) ~Set the metering switch to +25 and set the DMM to CURRENT range. ~Adjust the calibration control R39 (1-117) to read +250 uA at the DMM _ ~Set the metering switch to -25 ~Adjust the calibration control R31 (1-117) to read -250 uA at the DMM.

13) ~Remove power. Connect an ammeter in series with 25 ohm load resistor (min. 100 W ) between J2-1 and J2-9 _ ~Slowly apply power and observe load current. The load current should stabilize at A 14) ~Change the load resistance to 10 ohms (min. 250 W ) _ ~Slowly apply power and observe load current. It should stabi- Iize at A ~Set me tering switch to +1 _ ~Plug the DMM into metering jacks ~Adjust the calibration control R33 (1-117) for reading of +50 uA _ ~Set metering switch to ~I .

~Adjust the calibration control R34 (1-117) for reading of -50 uA _ 15) ~Remove the DMM from the metering jacks. ~Leave the ammeter in the load circuit and reduce the load resistance slowly Foldback current limiting should set in at approximately ~Short circuit the output completely Load current should be 25 or less_ Page of

M625B POWER SUPPLY Reference M625B Manual 1 ) Using WBS schematic LB 625-02-003 as reference, check the module for correct assembly with special atttention given to the following= Check that the "high" side of the AC Iine voltage is connected between P1-7 and the "Line" side of the circuit breaker Sw1 Check that filter capacitors C3 and C4 are wired for the correct polarity Check that the connections for power transistors 01 _ 02, 03 and 04 are wired correctly .

d) Ensure that both fuses blow) and size (ZA ) are the correct type (fast 2) ~Apply power and check for presence of approximately +40 Vdc at the output sides of fuses F2 and F3 _ 3) ~Remove power. Install Q1 and 02 _ (Left side heat sink when facing power supply) 4) ~Install temporary jumper across R11 on 1-117 to disable the complementary "loss of voltage" detector.

5) -Install 1-117 card_ 6) ~Monitor the +25 output at J2-1 and J2-5 . Apply primary ac power slowly using variac. If the output should not g0 into regulation by the time it reaches +27 V, adjust R1b (on 1-117) to reduce the voltage to +25 V 7 ) ~Remove power and install 03 and 04 _ when facing power supply ) (Right side heat sink 8 ) ~Monitor the -25 output at J2-9 and J2-5 _ The -25 output should go into regulation before the voltage reaches -27 V 9) ~Remove power.

Remove jumper form R11 on 1-117 Page of ISSUE APRIL/83

M625B POWER SUPPLY 16 ) ~Operate the supply with load current of A . ~Measure the noise across each half of the power supply output, as wel | as across the +25 terminals_ Noise should be less than 500 uV RMS . Use oscilloscope to check for possible oscillations_ 17) ~Remove power. ~Using 10 to 25 ohm resistor, short emitter to collector on Q1 or 02 _ ~Place voltmeter across the +25 V output (J2-1 J2-5) _ ~Slowly apply ac input with variac.

When the voltage reaches approximately 28 to 30 volts, the crowbar' SCR 09 (1-117) should fire and short circuit the supply output _ ~Repeat above for the negative output of the supply 18) ~Set the metering switch to OFFSET and connect the DMM to the meter jacks Switch DMM to VOL TAGE _ ~Apply power to the supply_ -Intermittently connect and remove the 10 ohm load.

The change in meter reading should not exceed +100 mV_ 19) DC VOL TAGE CHART The following dc voltages are typical and are obtained under no load conditions, with the ac input adjusted such as to result in an unregulated voltage of +40 Vdc . The voltmeter used should have minimum impedance of 70, 0oo ohms/volt. M625B Main Frame: Emitter Base Col lector 01 02 03 04 +25 +25 -40 -40 +25.5 +25.5 -39.5 -39.5 +40 +40 -25 -25 Page of

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