Kepco BOP Bipolar Power Supply Troubleshooting and Maintenance Guide

3.3 Requirements for output and sensing wires

The load conductor should be as thick and short as possible, and twisted in pairs to reduce magnetic field disturbance.

When remote error sensing is required, shielded twisted pair cables (minimum 20 AWG) must be used to connect the sensing terminal of BOP to the load end, compensating for a voltage drop of up to 0.5V per wire. Polarity must not be reversed.

All external programming resistors should use low-temperature drift, high stability metal film or wire wound resistors.

Remote programming troubleshooting

BOP can receive external voltage, resistance, or digital signal control through the rear programming connector (PC-12, 50 pin edge socket). The common problems are as follows:

4.1 Output nonlinearity when programming with external potentiometers or resistors

Reason: Wiring error or potentiometer resistance too high/too low. For the voltage channel, a ± 10V reference source (4mA maximum) is connected to the inverting input of PREAMP "A" through a 10k Ω input resistor. If a potentiometer is used, the total resistance should be about 10k Ω, and the voltage division method is shown in Figure 3-4.

Check: Confirm if the jumpers (1-8, 2-4, etc.) on PC-12 are connected correctly. If the local/remote flag (PC-12 pin 35) is grounded, the front and rear panel mode switches will be disabled and need to be set high to restore local control.

4.2 External 1V signal cannot drive BOP at full range

When the input signal is only ± 1V and full range output (e.g. ± 100V) is required, the gain of PREAMP "A" needs to be changed. The manual provides the formula:

Eo(PREAMP “A”) = –Ei × (Rf / Ri)，

The required output is ± 10V (BOP internal reference). If Ri=10k Ω remains constant, then Rf should be 100k Ω. Connect the external 1V signal to the corresponding pin of PC-12, and disconnect the original feedback network according to Figure 3-10, and connect the external 100k Ω resistor. If the signal source has high impedance, the in-phase input terminal of PREAMP "A" should be used (Figure 3-11).

4.3 No response from digital programming interface

BOP supports multiple digital programming methods: the old SN/SNR series, BIT 488/500 card, and the latest BIT 4886 card. Common faults:

BIT 4886 card communication failure: Check RS232 parameters (9600 baud, no checksum, 8-bit data, 1-bit stop bit). Is the GPIB address switch set correctly. Does the driver software support SCPI commands.

BIT 500 parallel card: Confirm that the data bus logic level (positive/negative) selects jumper wires (pins 1, 3, and 5), STROBE pulse width ≥ 2 μ s, and whether the BUSY signal is correctly detected.

SN 488 series: Confirm that the command format is the ASCII character "NCVVV", where N is the channel, C is the control character, and VVV is a hexadecimal or BCD number. Does the address match the controller.

TLD 488-16 system: CILL command syntax needs to be checked, such as FNC DCS: CH00 followed by SET VOLT 10, etc. Note that spaces and carriage returns must be correct.

Diagnostic prompt: All BIT cards provide optical isolation. If the output cannot be programmed, first measure the corresponding analog voltage on the rear programming connector (such as the Main Channel output should be 0-10V corresponding to full range). If there is no voltage, the digital card is not powered correctly or not placed in the REMOTE state (PC-12 pin 35 must be high, corresponding to the BIT card, the corresponding control pin is high).

Calibration and internal adjustment

BOP has been calibrated before leaving the factory and only needs to be readjusted after repair or replacement of components. The position of the potentiometer for internal adjustment is shown in Figure 2-1. Before operation, the load must be disconnected and the upper cover must be removed (note the high voltage hazard).

5.1 ± 10V reference voltage calibration

Connect the precision digital voltmeter to pin 22 (-10V) and pin 28 (+10V) of PC-12, with the common terminal connected to COMMON.

After power on, adjust R31 (+10V) and R32 (-10V) to make the reading accurate to 10.000V ± 1mV.

5.2 Zero point calibration of ammeter

Do not connect the load, connect the digital voltmeter to pin 10 (Io monitoring) and COMMON of PC-12.

Adjust R50 to read 0.000V. This signal corresponds to 0% of the output current.

5.3 Full range calibration of output current (R316/R314)

Connect the precision shunt and ammeter, place the BOP in current mode, and turn off the current control switch.

Connect an external 10V DC voltage source to the current programming input terminal (both front and rear panels can be used).

After power on, adjust R316 (R314 for BOP 200-1M) until the reading of the ammeter is equal to the rated value (for example, 4.00A for BOP 50-4M).

5.4 Linearization adjustment of optocoupler unique to BOP 200-1M

Use a function generator to output a 20Vp-p, 250Hz triangular wave, and drive the BOP to full range output through voltage programming input terminal.

Connect the oscilloscope probe to the testing point on the A1 control board (see Figure 3-32) and observe the waveform.

Adjust R15A to achieve optimal linearity of the triangular wave ramp (without bending or distortion).