Arfa Daily wrote:
hi

[quoted text clipped - 95 lines]

thanx all

Looking at www.eserviceinfo.com there are a lot of entries for Viewsonic
manuals. I only had a quick skim through, but there seemed to be lots of
listings for the e655 model which might be sufficiently similar to work by
??

The pincushion amp is likely to be discrete rather than a chip, and might be
based around FET on a small heatsink. Geometry correction waveforms are
often fed to it from that 'big' chip. I fear that you will not get too far
on this fault without a 'scope to look at the waveforms. I would absolutely
recommend against employing any kind of 'shotgun' approach at component
replacement, as you are likely to end up with more problems than you started
with.

As for the safety angle, I think you might be misunderstanding the relative
dangers of the HV generator circuitry, and the power supply. Whilst it is
true that the CRT's final anode will have around 25 kv on it, the source
impedance for this supply is relatively high. This means that the available
current at that voltage is quite limited. For sure, if you had a weak heart,
or managed to hang yourself right across that supply, receiving a shock from
it *might*, at a pinch, prove fatal. The much more likely outcome is a
stinging hand - probably with a cut across it where your hand collided with
the chassis during its rapid exit :-) - some words that are completely
new to your children :-) and wounded pride.

On the other hand, the switch mode power supply has around 380v dc on its
front end, and this is derived DIRECTLY from the incoming line voltage by a
bridge rectifier, so a relatively low impedance source with the current
limited *only* by the front end fuse, which is likely to be a 3 or 4 amp
ceramic type. This is enough to kill you. No joke. Fact.

So please take care around that area. Use an isolation transformer if you
have one. Makes life a little bit safer.

Arfa


hi

this is today's update...

i actually took the ridiculous desition of replacing all the electrolitic
caps as they are the first suspect of any damage to an old circuit. nothing
really changed, i think that the image quality increased but i'm not sure. i
also replaced ic no. 5 because while googling i found some datasheet that
says it's a dual op-amp so i thought that this would be the culprit, but
nothing so far.

an oscilloscope is a very very nice tool to have, but actually i'll be stuck
for a long while with the shotgun policy -which worked with me several. as
you are more knowledgable than me about monitors, i'll imagine that you're a
psychic and you can see inside my pistol and tell me whether the bullet is
close or far. i'll tell you all the details you need, you only have to give
the directions.

actually i don't have children, so don't worry about whatever vocab -i'm not
a minor either :-).

i'll follow this post with another listing all the discrete large triple
legged comonents, whether with heatsinks or not. and i'll try to google thier
datasheets also so stay tuned.

also please try to reply earlier because i waited for your opinion today
morning, and it could have taken a good part in my desition.

ok...

bye.

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