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| Thread ID: 30343 | 2003-02-16 22:32:00 | Monitors (again) | B.M. (505) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 121778 | 2003-02-17 21:06:00 | Yes Eric, up an around, a box of birds. (dead buggers) I think we can safely ignore the click, clacks, and shimmering on wake up. However, I’m still not clear on this “Screen Regulation” test and why the screen size changes different amounts on the different test patterns and what adjustment there is to correct matters. If someone’s got the time to briefly explain this phenomena it would be greatly appreciated. |
B.M. (505) | ||
| 121779 | 2003-02-17 21:15:00 | Oops :8} Sorry OldEric, no offense intended . My rather inelegant expression was intended to mean "off target" as in "steering in wrong direction" but I am familiar with the older meaning of the phrase and should have known better . B . M . and I have corresponded on a number of monitor related issues and B . M . having made his limitations clear, I have tried to keep my advice as straightforward as possible . Issues like screen regulation are not that important because unlike TV, unless gaming computer screens usually display a fairly static image . B . M . I hope your head feels better and I'm glad you didn't dig into the works while staticy . Alcohol and electricity are about as lethal as alcohol and motor vehicles . There will be a degaussing coil in there somewhere but it may not be all that obvious . You need to check the screen for lines in subdued light and in the absence of static:D as they can be quite faint . After checking you will have to reset the contrat & brilliance but no doubt you recall that the correct way to set these up is contained in my monitor FAQ . Cheers Billy 8-{) |
Billy T (70) | ||
| 121780 | 2003-02-17 23:13:00 | Hi B . M . In simple terms, screen regulation is the ability of the EHT supply to maintain a stable output voltage under varying loads (brightness levels and the relative illumination of the screen) . EHT supplies are naturally high impedance so in better quality monitors the beam current is monitored and a feedback voltage generated to instruct the EHT generator to work a little harder etc to apply compensation, thus keeping the screen image stable . If the EHT is not well regulated, high demand (for bright images) causes the voltage to drop and the scanning beam is not as "stiff," consequently the scanning circuits can move it easier and overscan will result, giving a larger image . Conversely, if the EHT beam current is low (dark sceen with very little illumination) the EHT rises, the beam is "stiffer" and a smaller image is produced . Screen regulation is also affected by the quality of the design of the scanning circuits as they are an integral part of the EHT generator, and also the regulation ability of the power supply under varying loads . All in all there are several factors that can affect the result you see on screen and I'll bet the different regulation characeristics you observed were caused by differing screen illumination characteristics for the two test patterns you tried . The regulation you describe sounds pretty reasonable to me and IMHO the bottom line is, if it ain't broke bad enough to worry you, don't try to fix it . Cheers Billy 8-{) Historical Note: On some early NZ colour televisions of UK origins the EHT regulation was so poor that there could be up to 3cm difference in scan size between maximum amd minimum brightness . Less than 2cm was considered a good one . :D |
Billy T (70) | ||
| 121781 | 2003-02-17 23:43:00 | Thanks Billy, (body now almost defragged.) Yes, I can confirm that the computer that this monitor is hooked to is not a games machine! (166 Pentium) I think the best bet might be to leave things alone and see what happens. If it were to go up in a puff of smoke there’d be no harm done as it was en route to the dump when intercepted. I’m still confused about the degaussing coil. I thought the loops of wire wrapped in tinfoil that follow the outer perimeter of the CRT were the degaussing coils? This monitor had no such refinements. In fact, I think it would be fair to say that it is a cheap & nasty as one could acquire. I’ve checked with Windows, Sandra, and Aida, and all report it to be “Unknown”. The irony is it produces the best picture! Well, better get comfortable for the Yachting, Bob |
B.M. (505) | ||
| 121782 | 2003-02-18 00:27:00 | Yes Bob, that is where the the coils are usually found, but even the cheapest monitor needs a degaussing system. Since it was OIWTTD when you "acquired" it, I guess it is possible that the coils were removed during a prior service but otherwise they may simply be a bit more discreetly positioned. Again, if it is working OK, don't worry about them. Cheers Billy 8-{) Don't sweat the petty things and don't pet the sweaty things :D |
Billy T (70) | ||
| 121783 | 2003-02-18 04:13:00 | I read in an earlier post here something about seeing widely spaced diagonal lines on the screen being caused by the A1 voltage being too high. I am servicing a monitor that is extremely bright, and the brightness controls have little effect on this, and these widely spaced diag lines are "very" visible even in bright sunlight. What is this A1 voltage mentioned, and what can I do to fix this issue? Cheers, Craig. |
craig_b (2740) | ||
| 121784 | 2003-02-18 04:24:00 | Oh dear Craig :( Yes, the lines you describe are the "flyback lines" I was telling B . M . about but in your case the cause is almost certainly a significant electronic failure . It is very unlikely to be curable by adjusting anything and you really neeed the services of an electronics technician . Don't leave it running like that as the excess beam current may kill your high voltage supply and that will be the end of your monitor unless it is under warranty or so costly it is with getting repaired . Cheers Billy 8-{) |
Billy T (70) | ||
| 121785 | 2003-02-18 04:28:00 | Thanks for that, but technically I am an electronics technician as I have graduated with an NZCE equivalent course this year!! I forgot to mention this was caused when the monitor was left on all day in the sun, and was VERY hot when the owner (not me) got home... It hasn't been used since except for me doing a bit of testing, and no the monitor is definately under no kind of warranty. Craig. |
craig_b (2740) | ||
| 121786 | 2003-02-18 04:51:00 | On the monitors circuit board, what am I looking for to identify the cause of the fault? You mention significant electronics failure - what do you mean by this? Craig. |
craig_b (2740) | ||
| 121787 | 2003-02-18 05:53:00 | Thank you again Billy. On that piece of excellent advice I shall consider it fixed! (Until next time) Cheers Bob |
B.M. (505) | ||
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