B+ voltage
 

im trying to fix a mitac L1450Pd monitor.
theres no picture but the heater is working and led is on.
i measured voltage from the secondary side of the chopper
and the + on the 160v cap.
i get 152v.
i then removed the HOT and placed a 240v 40w lamp across the collector
and gnd. the lamp lit up.
measured voltage again, still 152v.
is this problem in the power supply or somewhere else?

Do you have any high-voltage ?
You should have about 22 to 26KV on a 14"
monitor. If you have high-voltage, take a 1K
resistor and connect one end to ground using
a jumper cable. Touch the other end to the
cathode of one of the color video pins on the
crt socket. The screen should light up with that
color.
Also check the G1 and G1 voltages on the
crt socket. G1 should be about -20 to -60 volts.
G2 should be 300 to 600 volts.
Hope this helps...
John

You should check to see if you have drive pulses to the base of the
horiz output transistor, and to the HV drivers that are the output of
the HV generator. This is the next step.

Jerry G.
======

i reinstalled the HOT then tried the 1k resistor on the R G B pins
and nothing happened. measured the voltages of R G B and found 88v
measured G1 and G2 on crt neck board found G2 at 0v but G1 was -23.
G1 continued to drop to 0v. if i switch the monitor off/on i get
voltage at G1(100+volts then it drops back to 0v)
it sounds like the monitor is shutting down after switching on.

(tried the resistor on a working monitor and screen went
blue/red/green, G1 and G2 voltages 273v and -27v)


wrote:
Do you have any high-voltage ?
You should have about 22 to 26KV on a 14"
monitor. If you have high-voltage, take a 1K
resistor and connect one end to ground using
a jumper cable. Touch the other end to the
cathode of one of the color video pins on the
crt socket. The screen should light up with that
color.
Also check the G1 and G1 voltages on the
crt socket. G1 should be about -20 to -60 volts.
G2 should be 300 to 600 volts.
Hope this helps...
John

i reinstalled the HOT then tried the 1k resistor on the R G B pins
and nothing happened. measured the voltages of R G B and found 88v
measured G1 and G2 on crt neck board found G2 at 0v but G1 was -23.
G1 continued to drop to 0v. if i switch the monitor off/on i get
voltage at G1(100+volts then it drops back to 0v)
it sounds like the monitor is shutting down after switching on.

(tried the resistor on a working monitor and screen went
blue/red/green, G1 and G2 voltages 273v and -27v)

Jerry G. wrote:
You should check to see if you have drive pulses to the base of the
horiz output transistor, and to the HV drivers that are the output of
the HV generator. This is the next step.

Jerry G.
======