[TechAssist] Acer monitor 7176IE hor. drive not getting through [FIXED]

I had this unit fixed a few days ago but just haven't had time to post
the results.

The problem was a leaky HOT, 2SC5048. It
wasn't shorted, just leaky. I find that to be unusual as I have always
found HOT's to be either good or bad but hardly ever leaky.
Nevertheless, I should have
removed it to test instead of measuring it in-circuit and just taking it
for granted that it was ok when I saw some resistances between pins.


For anyone wanting the schematic for this monitor, go to:

ftp://147.213.74.111/schemy/

then click on MONITORY

and it will be in there.



Gary McCartney

McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: number63@xxxxxxxxxxxxx









My original message:


This is an Acer 17" monitor model 7176IE. There is no hi voltage. The
green light on the front operates as normal. When the computer goes into
standby, the green light turns to amber. When the computer is awakened,
the light goes back to green. Hear a relay clicking and the power supply
running but thats it. I do have a schematic.

I get a hor. rate square wave coming out of IC304 pin 7, 1.5V p-p. By
the time this signal reaches the gate of Q307 (IRF630) hor. driver, the
pulse is 0.8V p-p. There is 22.7 DC  Volts on the drain of Q307. Also,
all the other B+ lines appear to have proper or very close to proper
voltages. Should the amplitude of my hor. drive pulse high enough to
drive Q307? If so, why isn't the Mosfet conducting? If the pulse is too
low, is this monitor in some type of shutdown mode where it is not
allowing the pulse to be a greater amplitude?

Have changed Q307 and Q303, no differnce in operation. Also soldered
anywhere on the board that didn't look the best. HOT Q306 doesn't check
shorted.

Thanks for any help.
-- 



Gary McCartney

McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: number63@xxxxxxxxxxxxx
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