From Newsgroup: comp.sys.cbm

My A1200's monitor has died.

When I turn it on, it gives no sound, no picture
and even the power led doesn't come up.

However, when I look carefully, I can see
that my tablelight flashes just a tiny bit when I'm
turning the monitor on, so power must still be
going somewhere..?

I just moved the monitor from downstairs to upstairs.
No accidents, nor mishandling happened...

If anybody has any idea of the problem, please help :-)

thanks,
-tony caven (ferrara.c64.org)


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From Newsgroup: comp.sys.cbm

My A1200's monitor has died. When I turn it on, it gives no sound, no
picture and even the power led doesn't come up. However, when I look carefully, I can see that my tablelight flashes just a tiny bit when I'm turning the monitor on, so power must still be going somewhere..? I just moved the monitor from downstairs to upstairs. No accidents, nor
mishandling happened...

Tony,
It may or may not be related to moving it. Many electronic gadgets, especially those that generate heat, suffer from bad solder connections
that can open up at any time and cause intermittant or "dead set" symptoms.
A monitor is dangerous for a non-tech to work on. If you had some basic
skills and a bit of test equipment, I could walk you through some tests to
see what the problem might be. Otherwise, it's best to hand that monitor
off to the nearest qualified repair shop for an estimate.
Since the 3D can sync down to 15KHz -and- do VGA, it might be worth investing a bit extra in repairs as they are getting kind of scarce. If the monitor came on nice and bright and in focus when you turned it on before
the failure (indicating the tube is good), I would consider getting it
fixed. If, on the other hand, the tube came on slowly and a bit dim and/or
out of focus, the short life after repairs wouldn't justify the investment.

Ray

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From Newsgroup: comp.sys.cbm

A monitor is dangerous for a non-tech to work on. If you had some basic skills and a bit of test equipment, I could walk you through some tests to

I'm used to repairing C64's, 1541's and so on, socketing chips and
doing some basic soldering. I've got a Weller basic model with a very
sharp tip. Unfortunately I only got a multimeter as an equipment :-Z

If the monitor came on nice and bright and in focus when you turned it on

before

Yes I liked it's picture. I bought it for 55euros from the only finnish
Amiga dealer around and I only had the chance to use it for about
5 - 10 times before it died on me :-( (over a period of 2 months).

It took from half a second to a second for the picture to come up
whenever switched on, but I didn't mind that. Unless it was a
premature indication of a beginning fault ?

thanks,
-tony c


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From Newsgroup: comp.sys.cbm

If you had some basic skills and a bit of test equipment, I could walk
you through some tests

I'm used to repairing C64's, 1541's and so on, socketing chips and
doing some basic soldering. I've got a Weller basic model with a very
sharp tip. Unfortunately I only got a multimeter as an equipment :-Z

Tony,
That's enough to do some basic tests. Time for "Monitors 101". ;-)
First, try bumping it while it's turned on. A bad connection will sometimes show up during "percussive diagnostics". See if it will come on if turned
on it's side or back. Did the picture ever "glitch" or pull in from the
sides while running? All those are indicators of a bad connection
somewhere. If physical shock makes no difference, pull the plug and remove
the rear cover. Keep in mind the input filter capacitor(s) can hold a
charge for a long time if the power supply (usually a switcher) doesn't
start up for whatever reason. The power dip you noticed before is likely
the input filter charging... but that's all it does apparently. Measure
across that cap with your voltmeter to see if there is any residual voltage
on it with the monitor off. If it's zero, it's safe to work on. Use a 100W light bulb across it to discharge it if necessary.
Do a physical exam: look for an open fuse, swollen or leaking
electrolytic capacitors, or any part that looks overheated or charred. Do
you notice any smell of something overheating? Inspect the foil side of the main board for bad solder connections. They show up as tiny cracks around
the leads of large components like the flyback (called a line output transformer in Europe), on large heat-sinked devices such as power
transistors and ICs, big diodes, and any resistor of 1 watt or more. I
always do that first when repairing a monitor, then look for other
problems. Sometimes, that's all that is needed.
If there are no blown fuses or burned parts, measure across the input
cap with the monitor turned on. Listen closely to notice any high frequency whistle or ticking sound... indicators that the supply is trying to work
but might be looking into an overload. See if there is any B+ voltage on
the HOT (horizontal output transistor) collector (the center lead). The negative meter lead should connect to input filter cap negative or to that transistors emitter lead, not to chassis ground. If there is no voltage
there, shut the monitor down and pull the plug. Check from collector to
emitter of the HOT with your ohmmeter. It should measure like a diode one
way and open the other (meter leads reversed). Note that base to emitter
will always measure low resistance... that's normal. If the collector is shorted, there are several possibilities including a bad flyback, shorted
yoke, shorted diode on secondary side, etc. If it checks OK, the problem is likely confined to the low voltage supply. You could "shotgun" all the electrolytics but beyond that, time to call in some heavy duty help. Bottom line: burned or shorted components and/or open fuse mean an overload;
monitor dead with no burned parts usually means something opened up.

Ray

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From Newsgroup: comp.sys.cbm

All right, thanks very much for the tips, I'll look into them
later. Meanwhile I cannot even pry the case open... :O)
I've opened the three screws on the bottom but there seems
to be something holding the upper part. I've tried pressing,
lifting, twisting and shouting but nothing helps :O)
argh, i'm soo lame :-)


-Tony Caven

If you had some basic skills and a bit of test equipment, I could walk you through some tests

line: burned or shorted components and/or open fuse mean an overload;
monitor dead with no burned parts usually means something opened up.

Ray

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From Newsgroup: comp.sys.cbm

I cannot even pry the case open... :O)
I've opened the three screws on the bottom but there seems
to be something holding the upper part.

Tony,
Newer monitors don't use screws to hold the top of the cabinet back in place, but instead use two plastic "snaps" at the inside case top. You can sometimes see where the latches are by sighting along the top and looking
for a bit of deformity of the front half shell over those spots. Some
latches are accessible with a special tool (or long thin screwdriver)
through tiny holes in the cover. Others just require the correct pressure
be applied over the internal latches while pulling on the rear half shell. Alternatively "bumping" the latch points with the heal of your hand until
they pop loose while pulling out on the bottom half shell usually works.
Talk about a black art...

Ray

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