Any ideas on monitor screen shake?

It's nearly impossible to give you an exact part to check or replace but my guess is a loose connection. A copper trace has come undone and is acting like a thermostat. When the unit warms up, it makes contact and normalizes the picture. At times, a physical shock kicks it loose again until another shock puts it back.

If you want to do this yourself, I'd wish you luck. I've traced a lot of loose connections in my time and it can be a real challenge. A good magnifying glass is a big help but so is a good multi-meter. Since the symptoms appear when the unit is cold, let it cool down before tracing. Don't switch it on while testing since the symptom will disappear after a few minutes.

If you don't want to do this yourself, take it to a good service shop that you can trust.

regards,

Vulcan

I agree with Vulcan - this is very probably a bad connection - maybe a cracked track or bad solder joint.

As this is a CRT monitor, the same warnings apply as for mucking about in CRT TV sets:

There are capacitors inside which carry a lot of charge at high voltage - they can pack a lethal belt long after the power has been disconnected - please be careful.

I'd suggest trying the simplest approach first - disconnect and reconnect all the connectors - it could just be a bit of oxidation.

The CRT itself can also knock you on your butt.

I agree with others that it's time to let it die and get a non-CRT monitor.

On the other hand, I have fixed dozens of monitors by re-soldering connections. The most common points seem to be where the yoke connector and/or the flyback transformer are soldered to the driver board. If you don't know what those terms mean, then you should not be fooling around inside a CRT device! I don't quite agree that the shocks from a CRT are lethal, (unless you already have a weak heart, etc.), but they definitely CAN leave you lying on the floor, gasping for breath, etc. And in dry climates, this can occur MONTHS after the unit has be disconnected from power. I found that out the hard way!

One is suppose to always discharge the capacitor attached to the CRT before servicing.

It's not a capacitor attached to the CRT, it is the CRT itself that IS the capacitor. There is a conductive coating on the outside (usually DAG -graphite), and a coating on the inside, (commonly aluminum), which, together with the glass envelope as a dielectric, constitute a capacitor. Connecting the anode connection (the inside conductor) to ground (the outside conductor) discharges that capacitor. It was over 50 years ago that I discovered that this capacitor could hold its charge for months...

dkwarner

http://en.wikipedia.org/wiki/Cathode_ray_tube#High_voltage

From your link:

"High voltage

CRTs operate at very high voltages, which can persist long after the device containing the CRT has been switched off and/or unplugged. Residual charges of hundreds of volts can also remain in large capacitors in the power supply circuits of the device containing the CRT; these charges may persist. Modern circuits contain bleeder resistors, to ensure that the high-voltage supply is discharged to safe levels within a couple of minutes at most. These discharge devices can fail even on a modern unit and leave these high voltage charges present. The final anode connector on the bulb of the tube carries this high voltage." (my underlining, except in the link)

The capacitors referred to in the second sentence only have a few hundred Volts, and are NOT connected to the CRT. The CRT itself can have tens of thousands of Volts.

The final anode connector on the bulb of the tube carries this high voltage.

I mistakenly thought a capacitor held this high voltage at this anode, but I did know that you had to discahrge it at that point and the voltage is around 32,000V.

Very Good!

"I mistakenly thought a capacitor..." You were only partly mistaken! It is a capacitor, but the capacitor IS the CRT itself, rather than a separate item.

The voltage on the anode depends on the size of the CRT and the brightness. A 9" monitor may be in the 10-15 kV range, while as you say, larger ones may use 30-40 kV or even higher for very large ones.

Yes, put it on the desk and take a break from holding it! IQ

It is probably the horizontal oscillator circuit.

As lynlynch said, let it die!

Thank you all for your great input - I'm not in any way interested in fiddling with the insides cos I have no idea what I'm doing so I'll take up the replacement suggestion and get another one - and thank you all again for your time and trouble.

Why don't you register, and hang around some? You seem like an OK OP.

I have a cheap electric fan with a plastic housing that doesn't provide any magnetic shielding. If it's near the monitor, I see the same effect.

I think it has lived its life. I had to replace my monitor after 5 years of use. My Hardware man advised me to replace it as it could not be repaired.

Suresh Sharma.

IF YOU CAN DO IT SAFELY, You can run the monitor with he cover off and tap around the board with an insulated tool to zero in on the intermittant part or connection. If you're not very good at this, the likelyhood of getting hurt or ending up dead is quite high! Realize an lcd monitor uses about a fourth or fifth of the power a crt uses and an lcd doesn't generate X-rays. If you use this monitor a lot, a new one should pay for itself in a year or two. Hows that for a reson to replace it?