ravi@mcnc.UUCP (Ravi Subrahmanyan) (01/18/87)
[ What? Another poodle? ] This concerns the recent spate of postings of programs that lurk in the innards of our hapless ST's and blank the screen after a few minutes of inactivity. As far as my understanding goes, when the ST blanks the screen, it cuts down the video signal going to the monitor. Now all this would do on a monitor is suppress the beam from the electron-gun and prevent it from striking the screen. So, even though one doesn't see anything on the screen, the gun is still churning out electrons. This therefore saves the screen phosphor, but the gun filament still wears out. Is this a consideration? Would turning down the brightness and contrast in addition to letting the program blank the screen be any better (I don't think so)? From what I remember from my oscilloscope days, the life of the filament is as important as that of the phosphor, ie. picture brightness is a function of both and so saving on one may not be helping as much as we may believe from the blanked screen. Or, are these just the blabberings of an outdated education (after all, I >am< almost in my mid-twenties.. oh, those days of youth.. gone forever! (sigh :-) -ravi
cabbie@chinet.UUCP (01/19/87)
In article <1962@alvin.mcnc.UUCP> ravi@mcnc.UUCP (Ravi Subrahmanyan) writes:
This concerns the recent spate of postings of programs that
lurk in the innards of our hapless ST's and blank the screen after a
few minutes of inactivity. As far as my understanding goes, when the
ST blanks the screen, it cuts down the video signal going to the monitor.
Now all this would do on a monitor is suppress the beam from the
electron-gun and prevent it from striking the screen. So, even though
one doesn't see anything on the screen, the gun is still churning out
electrons. This therefore saves the screen phosphor, but the gun
filament still wears out.
Is this a consideration? Would turning down the brightness
and contrast in addition to letting the program blank the screen be
any better (I don't think so)? From what I remember from my
oscilloscope days, the life of the filament is as important as that of
the phosphor, ie. picture brightness is a function of both and so
saving on one may not be helping as much as we may believe from the
blanked screen. Or, are these just the blabberings of an outdated
education (after all, I >am< almost in my mid-twenties.. oh, those
days of youth.. gone forever! (sigh :-)
-ravi
With all of the ramblings on and on about color monitors and
why you should blank the screen/turn off the monitor/rotate the colors/etc.
ad nauseum, I have to express my own observations.
Some time ago an article was published in the "Computer Shopper" in
regards to this. In summary the author stated that turning off the monitor
was bad for the CRT because the constant heating and cooling of the filament
would cause eventual failure of the filament itself. The basis of this was
a standard household light bulb. Not true! I have been in the video business
for several years now and have yet to see a filament fail under those condi-
tions. I can truthfully say that I have only seen 1 CRT filament that was open
and I don't know if that was done on purpose (115 VAC applied to the fila-
ments?).
I have seen 1 Plumbicon tube with an intermittent heater connection and that
tube was questionable at best. At the TV station where I work we have several
monitors (15-20) that have been on 24 hours a day seven days a week for the
last 8 years now and have no problems with the CRT's on any of them. The
CRT's do get weak after several years but we do have a rejuvenator that solves
that problem at least temporarily. I have worked prior to that in several
TV shops where the TV sets were turned on and off several times a day and have
experienced no problems with this type of operation either. There is an
advantage to blanking the screen when not using the monitor for an extended
period of time (read 15-60 minutes). To prevent the image from getting burnt
onto the screen one should blank the screen after about 10 minutes of non-use.
Turning the monitor on and off several times a day will not hurt the CRT either.
The most common CRT problems are:
1) Cathode shorts (bad manufacture/design)
2) Gassy tube (old age)
3) Burnt phosphor due to exposure to direct sunlight
4) Anode (HV) shorts (relativly rare)
5) Weak tube due to age and/or use.
6) Burnt phosphor due to excessive brightness
Yes even Sony trinitrons are subject to failure. I have replaced
several of them due to any of the above conditions. The technology of
monitor and television design has increased over the last several years.
The most common failure now is the Horiz. output transistor and or the
rectifiers to provide 150 VDC for the horizontal section. Occasionally
a horiz. output transformer will go bad but that is not too common any more.
The sets that had a real problem was certain RCA and Sylvania sets. Zenith
had a problem with a capacitor on their chromacolor II sets that would allow
the HV rise to unbelievable levels. (one was documented at 58kv) But that
is another story. (War story? (:>) )
Ravi, don't take this as a flame. Your article just happened
to be a good place for me to express my experiences.
In summary this entire subject has caused much unneccessary
concern. If unattended, the monitor screen should be either blanked
or the entire monitor should be shut off depending on how long the
monitor will be left un-attended so as to prevent burning of the phosphor.
--
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Any opinions expressed above are my own. Rich Andrews
They can be yours too. Please send $19.95 to.....ihnp4!chinet!cabbie
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