Service manual

Troubleshooting AC-Turn-On Circuits

Relay AlK1 closes at 1.0 seconds and DROPOUT goes high at 1.1 seconds after 20V (5V UNREG) reaches about 11Vdc.

DROPOUT high enables the PWM if OVERVOLTAGE , INHIBIT , and OVERTEMP are also high.

Circuits Included. AC-Surge-&-Dropout Detector, Bias Voltage Detector, U11A, 1-Second Delay and Relay Driver--all on

A2 control board.

Setup. The Main Troubleshooting Setup, Page 48. Apply the ac mains voltage to the bias transformer, and set the external

supply to 0Vdc.

Inputs:

NODE (+) * SETUP MEASUREMENT SOURCE

A2J3-1 wait 2s 5.0Vdc A2Q3 (emit.)

A2J3-22 20Vdc A1CR6, A1CR7

A2U20-8, 10 f.w. rect, 1-2V pk A1CR8,A1CR9

A2U22-13 TTL sq wave, 20KHz A2U22-6

Outputs:

NODE SETUP MEASUREMENT

A2U20-5 cycle power transition 0 to 13.5Vdc

A2U20-2 cycle power transition 0 to 1.4Vdc

A2Q6-1 cycle power transition 0 to 5.0 to 0.3Vdc

A2Q6-9 cycle power transition 0 to 0.3 to 5.0Vdc

A2U20-6 wait 2s < 0.25Vdc

A2U20-1, 14 wait 2s Hi (5Vdc)

A2U11-3 cycle power transition Lo to Hi to Lo

A2U18-10 cycle power burst 1.25khz sq. wave, 1.1s

A2U18-13 cycle power five 100ms pulses then Hi

A2U18-12 cycle power two 200ms pulses then Hi

A2U18-15 cycle power transition Lo to Hi at 800ms

A2U17-8 cycle power transition Lo to Hi at 1.0s

A2U17-11 cycle power transition Lo to Hi at 1.1s

(

DROPOUT )

A2Q5 (col.) cycle power transition 5.0 to 0.3Vdc at 1.0s

(RELAY ENABLE)

Troubleshooting DC-To-DC Converter

Parallel NOR gates A4U2A, A4U2B and A4U1A act as drivers and switch on PFETs A4Q3 and A4Q4 through pulse

transformer A4T1. NOR gate A4U1B turns off the PFETs through pulse transformer A4T2 and transistors A4Q1 and

A4Q2.

Circuits Included. On-Pulse Driver, Off-Pulse Driver, PFET Switches and Drivers on A4 power mesh board.

Setup. The Main Troubleshooting Setup, Page 48. Apply the ac mains voltage to the bias transformer, set the external

supply to 40Vdc, and switch on the LINE switch. Set the unit's output voltage to 20Vdc and current to above 1Adc. Verify

that the OVERRANGE LED lights. See Figure 3-7 for waveforms.