Service manual

T r o u b l e s h o o T i n g T r e e s • C o m b i t h e r m C t e x p r e s s t e C h n i C a l s e r v i C e m a n u a l • D – 21

troubleshooting trees

No Display/Control not powering on (Unit Dead)

Is voltage across L1/L2 at

main TB?

Is voltage across terminal

1/F1 and terminal 1/F2

6.3A fuses?

Is voltage across terminal 2/F1

and terminal 2/F2 6.3A fuses?

Check cord/plug/main

circuit breaker – Install/

Repair/Reset as needed

Yes

Repair wiring between

main TB and F/1F2 fuses

Yes

Replace blown F1/F2

fuses(s)

Repair wiring between F1/F2

and Power Supply

Is voltage across L1/N at

power supply?

Is 12 VDC across terminals

V+ and V- at power supply?

Replace power supply

Is there 12 VDC across

pin 1-2 on On/Off board?

Test On/Off board cable for

continuity. If cable ok, replace

display board

Is 12 VDC across display

(LCD) terminals DB3 and

DB1?

Repair wiring between power

supply and LCD

Test On/Off board -

On = Temporary switch between 1-3

Off = temporary switch between 1-4

Yes