M
makden
I have this CRT monitor for some more than a year and it worked just
fine. A week ago it died and the first troubleshooting showed defective
deflection transistor (2SC5440) and its supply resistor (4.7 Ohms) was
gone too. There is no place on the earth where I can find a circuit
diagram for this monitor and the NEC rep forwarded me to their service
phone number. There is no way I will ship this 50 Lbs monster somwhere
else than the trash can I said but I can't forget the crisp picture and
the perfect geometry it had. The further troubleshooting (after I
replaced the defective components) showed that the +50 Volts power
supply (probably in Stand By mode) increases to +100 Volts for a couple
of seconds while the High Voltage Flyback transformer starts working (I
can hear the CRT cracking sound when it gets 25KV load) and everything
goes back to the previous state and down to +50 Volts and stops
working. I am really limited to continue the troubleshooting without
any service manual except some blind replacing electrolytic capacitors
but maybe someone has some more experience to give me a hand here to
shorten my fruitless efforts to fix this monitor. Thanks for any idea
in advance and best regards to all the participants in this group.
fine. A week ago it died and the first troubleshooting showed defective
deflection transistor (2SC5440) and its supply resistor (4.7 Ohms) was
gone too. There is no place on the earth where I can find a circuit
diagram for this monitor and the NEC rep forwarded me to their service
phone number. There is no way I will ship this 50 Lbs monster somwhere
else than the trash can I said but I can't forget the crisp picture and
the perfect geometry it had. The further troubleshooting (after I
replaced the defective components) showed that the +50 Volts power
supply (probably in Stand By mode) increases to +100 Volts for a couple
of seconds while the High Voltage Flyback transformer starts working (I
can hear the CRT cracking sound when it gets 25KV load) and everything
goes back to the previous state and down to +50 Volts and stops
working. I am really limited to continue the troubleshooting without
any service manual except some blind replacing electrolytic capacitors
but maybe someone has some more experience to give me a hand here to
shorten my fruitless efforts to fix this monitor. Thanks for any idea
in advance and best regards to all the participants in this group.
