Robin Taylor wrote:
hi

my monitor has pin cushion effect problem, and the picture edges are out of
the view. the monitor controls don't solve it as the (horizontal size)/
(pincushion\trapezoid) controls don't have effect anymore.

Em,. Two thoughts one look for a big diode in front of the line output
transistor or close to the Line OutPut Transformer. When these break
down, they cause the width to go out.The screen gets really wide.

If the screen height is collapsing maybe check for something like a
TDA1675 and associated components, in particular diodes.

Best regards,

Robin

this is the follow up with the discrete transistors i found inisde the
monitor. there are exactly five components of this description, three are
FETs and two are BJTs, and all the rest transistors inside are small TO-92
BJTs, all of them are BJTs. the FETs are all near the power collection, one
just right after the big 220uf/400v cap and it have a big heatsink, i guess
it's a chopper, the second looks nearly the same and is located just beside
the smps transformer, i guess it's a chopper too. the last one is without a
heatsink and is locate nearer to the tube connectors.

BUT on the other hand the BJTs are locate just beside the tube connectors,
particularly beside a plug that is 1x4 grid of connectors, the wires in it
are brown-yellow-blue-red from right to left.
so i guess one of these transistors or both of them are responisble for what
happened.

thier numbers are;

1. C5248 2. 0669A both of them are NPN

the one FET that is near the tube connectors is;

3. 1RFG30

i googled for datasheets, the only one i found was no. 1's datasheet, it
states that it's "High-Voltage Switching (Audio output amplifier transistor,
stabilized power supply transistor)"
and i think this is the one. the thing is i tested the BJTs and they seemed
to be operational, i'm not sure but i know how to test a BJT with an avo
meter.

also the no. 1 transistor is attached to a metal frame mounted on the pcb
with tin solder, rather than attached to a heatsink.

i'll try to replace them and see what happens, i hope i find them all on the
market. i don't know what viewsonic was thinking, manufacturing it's products
with these ancient components. it seems as they manufactured these things in
the ice age, then stored them into the ice, and when the ice melted by the
global warming, they got them out and began selling.

whatever..........

as for the image, actually it's not collapsed i'd rather say that it's
widened but not so much. it looks like a chair that someone was sitting on
then stood and the cushion on the chair didn't return back to it's normal
shape. it just stayed compressed inside, the image just looks like that, with
it's outer corners wider than the middle and spreading outside the view. they
call this simptom pincshion effect, also if you were following the horizontal
size doesn't have any effect whatsoever.

actually there is that diode just after the smps transformer but i don't know
exactly if it is operational or not as it didn't grab my attention. i'll
check on it in the morning.

thanx for the ideas

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