Re: Monitor keeps going into standby mode

On 31 Oct 2006 07:26:00 -0800, "gavspav" <gavspav@xxxxxxxxx> wrote:

Thanks for the responses.

I have checked the external power supply and it is fine.

Can't see any broken wires.

Don't know how old the unit is as it was bought off ebay a few months
ago. Looked new when i got it though.

I do get alot of mad flickering sometimes before it goes into standby.

Thanks,

Gavin

You sorta hafta look at the horizontal with a scope. There's an
internal horizontal oscillator. It cooks along well below the real
horizontal signal frequency wise. The Hsync signal from the computer
comes along and triggers a new horizontal refresh line before the
internal oscillator would on its own.

Lose the horizontal sync, and the monitor's internal oscillator runs
for a bit but at a lower frequency (that you hear), the big brother
circuit kicks in and says go to standby we ain't got the right drive
signals.

Doesn't have to be a wire - but that's a place to start.

Any circuit board connection to the Horz or Vert sync signal
amplifiers could cause similar symptoms.

Many monitors use single integrated circuits for each - the horz and
vertical drivers. Both are usually high power devices. They are
mounted to heatsinks. A common problem is the heatsink expands with
the warm-up and stresses the leads to the device - eventually breaking
the solder joint. Both heatsink and IC are mounted to the board - but
expand at different rates with temperature. Re solder all the
connections to those parts will sometimes fix that problem.

It is unlikely that anyone reading about it will give you the right
answer - you are in the driver's seat and have to think it through.

I've fixed a lot of monitors and both the vertical and horizontal
driver circuits fail frequently. (the monitor I'm using now has had
both problems). Power circuits are another weak link - increase the
60-50 HZ ripple on a monitor PS and it starts modulating the 60-70 HZ
free running vertical oscillator.

Nine times out of nine it is the construction technique and design
that cause problems - very seldom a part failure (except
electrolytic's in the PS). They "wave solder" the boards in mass
production - but not all connections are happy with just a taste of
solder. The larger leads and problem areas need more heat for a good
solder joint.

Then we have the old ViewSonic monitors . . . they hang ten pounds of
tweaking hardware (coils and pots for pincushion gun drive etc.) on
the connector to the CRT - they all die prematurely

Very few component failures for me - but lots of bad solder joints.

If you could describe the sound better - that might be a clue.

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
.

Relevant Pages

  • Re: Sun Monitor Tuneup - how?
    ... > equipment to be difficult to repair, Im guessing they apply dummy circuits ... > You know about high voltage thats still in the chassis even after the power ... put more running monitors close to it. ... >>metal shielding, with circuit boards mounted to the inside of the ...
    (comp.sys.sun.hardware)
  • Re: Sun Monitor Tuneup - how?
    ... > equipment to be difficult to repair, Im guessing they apply dummy circuits ... > You know about high voltage thats still in the chassis even after the power ... put more running monitors close to it. ... >>metal shielding, with circuit boards mounted to the inside of the ...
    (sci.electronics.repair)
  • Re: What does flashing green/amber on my Viewsonic PT795 mean?
    ... from its normal green to an alternating amber ... At that time, power cycling cleared the problem, but yesterday it ... Could be as simple as a cracked solder joint, ... I tried rapping it reasonably hard, but perhaps not hard enough or in the ...
    (sci.electronics.repair)
  • Re: What does flashing green/amber on my Viewsonic PT795 mean?
    ... from its normal green to an alternating amber and green, for which the manual has no explanation. ... At that time, power cycling cleared the problem, but yesterday it happened again, and this time it's apparently for good. ... Could be as simple as a cracked solder joint, ...
    (sci.electronics.repair)
  • Re: Mitsubishi big screen picture goes black
    ... Could be anything from a relatively inexpensive bad solder joint to a ... catastrophic repair. ... Leonard ... If I wait a few minutes, I can power the tv ...
    (sci.electronics.repair)