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| Thread ID: 45136 | 2004-05-11 08:47:00 | Monitor Shrinks and Flickers | damfr458 (5636) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 235768 | 2004-05-11 08:47:00 | I have a PC Company 17" flat-screen monitor set at 1024x768 @ 85Hz and after about 2.5yrs the screen image shrinks from both sides and sometimes flickers...this would appear for about a second or two and at no regular intervals. Can anyone help me with this. Thanx. |
damfr458 (5636) | ||
| 235769 | 2004-05-11 09:02:00 | welcome to F1 sound like your monitor is on the way out. |
robsonde (120) | ||
| 235770 | 2004-05-11 10:02:00 | Hi Fredrik Yes, your monitor is probably showing signs of old age. The fault is probably repairable, especially if it is done before total failure occurs. Problem is, the cost of the repair could exceed the value of the monitor if it takes a while to trace the fault. You might be better off to buy a replacement and get at least a year of warranty. Cheers Billy 8-{) |
Billy T (70) | ||
| 235771 | 2004-05-11 10:21:00 | Maybe its degausing itself? | KingWave (5517) | ||
| 235772 | 2004-05-11 11:06:00 | Unlikely KW, degaussing makes quite a "Boing" noise as the field hits the shadowmask but it doesn't make the picture size change. two different effects really, and this problem sounds like a scan correction/width-circuit fault. I had a Hyundai that did that and I was too lazy to go inside & fix it. In the end it died the death and when I did the post mortem I found I could have fixed it in five minutes. A series of dry joints were the cause, but it isn't always that easy to see what's wrong. Cheers Billy 8-{) |
Billy T (70) | ||
| 235773 | 2004-05-11 11:20:00 | Billy, I often wonder where the "boing" noise actually comes from, which component(s), any ideas on that? | Terry Porritt (14) | ||
| 235774 | 2004-05-11 11:22:00 | My cheapie 17 in monitor does the same thing, along with some colour problems. A good wack on the top edge seems to sort it for a while. But definately on the way out, got a new 17in LCD arriving next week to replace it. Then I can drop kick the old hunk of crap down the driveway. :-) | Sb0h (3744) | ||
| 235775 | 2004-05-11 21:52:00 | > Billy, I often wonder where the "boing" noise > actually comes from, which component(s), any ideas on > that? Two degaussing coils surround the perimeter and rear bell of the CRT. (these days it is more often a single coil) and the degaussing circuit applies a very high pulse of 50Hz alternating current to these coils. The pulse has a very fast rise time because it is working into a very low impedance circuit, then a simple NTC thermistor in series with the coil(s) causes the current to die-off exponentially. Some circuits use other arrangements but the net effect is the same. The electromagnetic field generated by this pulse is very strong, probably in the vicinity of 6-10 kilogauss at the centre of the coils (I just measured a 2 kilogauss peak 100mm from the centre of the screen on my Philips 107S monitor) and apart from removing stray magnetism, which is what degaussing is all about, this field pulse causes the shadow mask and any associated ferrous metal to vibrate with the same exponential field strength vs time characteristic, hence the boing you hear. Screens with an aperture grille (such as the Sony trinitron) make a slightly more musical "proing" because the grille is rigid in the Y axis only so it is more able to resonate. I trust that this explanation satisfies your curiosity Terry. As ever, it is a simplified explanation only, and there is a little more science behind your boings or proings.:D Cheers Billy 8-{) |
Billy T (70) | ||
| 235776 | 2004-05-12 00:59:00 | So, if it is the internals of the tube that go 'boing', as I half suspected it must be, it's a wonder that pieces dont come adrift or fall off in time, they will at least be subjected to some magnetostriction and temporary dimensional changes. It's amazing that things are still aligned mechanically after degausing. |
Terry Porritt (14) | ||
| 235777 | 2004-05-12 05:55:00 | "boing"? "boing" ?:| According to the authority (Moriarty) "You got to go owwww (www.spidersweb.freeserve.co.uk)". I worked with pulse transmitters (100kW peak). Each pulse made a "tick". I reckoned it was the tank coils and output link coil moving. (Flash overs in fault conditions sounded quite different. They went BANG;-)) |
Graham L (2) | ||
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