K15 Power Supply Test Procedure

Manufacturing Checkout Procedure

The Korad K15 power supply is designed for use with the K15, KWD and KHD series lasers. The function of this supply is to charge the storage capacitor bank to a selected voltage at a fast rate. For a complete description of the K15 supply and controls, see the "K15 Power Supply Instruction Manual".

The purpose of this procedure is not to describe the K15 supply, but instead, provide an easy and safe method of testing and calibrating the supply. For this purpose, a special test fixture has been provided to test the supply.

Equipment Needed

K15 test fixture
Oscilloscope
5 kilojoule head with lamp and heat exchanger
DC hypot

Hookup

Connect the supply to the test fixture as shown in figure 1.

Short Circuit Test

Before plugging in the 240 volt line plug, turn the power switch (on the supply) on.
Place a Ohmmeter across the 240 volt line (across the switch terminals is convenient) and read approximately 12 Ohms.
Place a Ohmmeter from one switch terminal to ground and read greater than 2 megohms.
Repeat the above step for the other switch terminal.
Turn supply power switch off.
Plug 240 volt line connector into outlet.

To Test The Interlock

Set the controls on the K15 test panel and the power supply controls as indicated and verify the following conditions

Test Panel Controls

Supply Controls

To Test The Controls

K15 Test Panel Controls

Supply Controls

To verify ground point and 120, 240 points: set the controls on supply as indicated, then rotate S2 from 1 through 3 and verify that the conditions indicated occur.

Power Supply Controls

K15 Test Panel Controls

To verify test points out of S1

Set the power supply and test panel control as indicated in the tables. These controls will remain constant while verifying these outputs but note other controls will vary

Supply Controls

K15 Test Panel Controls

Set the controls (variables) on the power supply and K15 test panel as indicated. Connect the oscilloscope to S1 and verify the outputs and other conditions

Test Panel Controls - Power Supply Controls

To Calibrate the Rep-Rate Circuit

Turn the supply off and remove the SCR control assembly card.
Solder a 10 Meg Ohm resistor (1/2 Watt) R9 on the card.
Place the SCR control card back in the supply.

Set the test panel and supply controls as indicated

K15 Test Panel Controls

Power Supply Controls

Connect the scope to S1 on the test panel with time base set at 1.0 sec/cm sensitivity at 10 v/cm and sync. Source to internal sync.
Turn the PPM dial completely counterclock wise.
Push the auto button and verify that the spikes approximately 25V in amplitude occur.
Adjust R1 on the SCR control card until the spikes are 1.0 cm apart.
Turn the PPM dial clockwise until the spikes are 2 cm apart.
Loosen the set screws and remove the PPM dial point the arrow to 30 PPM and tighten the set screws.
Set the time base on the scope to 2 sec/cm.
Turn the PPM dial to 10 PPM and verify that the spikes are 3 cm apart.

To Test the Trigger Circuit

Set the test panel and power supply controls as indicated

K15 Test Panel Controls

Power Supply Controls

Set scope sensitivity to 2 volts/cm time base to 2 milliseconds/cm and sync. On auto or internal.
Connect the scope 20 J3 on the test panel and verify an output similar to the shown below about 7v peak.

With the exception of the kilovolt dial, leave the control as in the above and below figures. Turn the kilovolt dial to zero and verify that the waveform show above goes to zero and back to its original value as shown below

To Test and Calibrate the High Voltage Supply

Set the test panel and power supply controls as indicated.
Push the manual button and verify that supply charges to 1.00 KV and stop.
If not, push dump button at 2.0 KV.

Test Panel Controls

WARNING

At this point, very high voltages will be presented in the supply when the manual button is depressed.

Power Supply Controls

With the exception of the kilovolt dial, leave all controls as above. Turn the kilovolt dial to 3.00 KV push the manual button and verify that the supply charges to 3.00 KV and stop. If the supply reads high or low, push the dump button, adjust the R12 (on logic card) push the manual button to recharge the supply. Repeat this process until the meter reads 3.00 KV exactly.
Repeat the above step with the kilovolt dial set at 4.0 KV.
Push the dump button to discharge high voltage.

Operational Test

Connect a 5 kilojoule head (with heat exchanger) to the lamp connector in the back of the test fixture.
Set the controls as in the above 2 tables and have the kilovolt dial set at 4.00 KV push the manual button and verify that the supply charges and fires the lamp automatically at 4.00 KV
Make note of the shot counter reading.
With the controls set as in the above 2 tables and the kilovolt dial set to 4.00 KV, verify PPM dial is 10 PPM, push the automatic button and verify that supply charges and fires automatically every 6 seconds for 5 minutes.
Verify that the shot counter has advanced.

To Select a H.V. Shutdown Resistor

Turn the HV switch (S5) on the test panel off.
Turn the supply off and discharge the capacitor bank.
Disconnect the cable from J4 (H.V. Out).
Connect a DC hypot across J4, or any point common to J4, and ground the hypot should be a negative supply with a positive ground.
Hook a variable resistor or a resistance substitution box (about 20 K to start) across K2 pin 2 and ground.
Set the kilovolt dial to 5.00 KV, make sure S5 on the test panel is off; all other controls on the test panel may be disregarded at this point.
Turn the supply's power switch on.
Push the charge button. No H.V. Voltage will be present.
Turn the hypot on and increase the voltage to 5.3 KV. Note that the meter on the supply will read off scale.
Increase the variable resistor across K2 pin 2 until the supply automatically dumps itself. Quickly turn the hypot voltage to zero to prevent excessive current.
Measure the value of the resistance and replace it with a fixed resistor as close as possible with the same value.
To Remove Supply From the Test Fixture

Turn supply off. Use the discharge rod to discharge the capacitor bank.
Remove the supply from the test fixture.