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Another observation: Normally when you wake the monitor from standby you hear the relay click at the exact second the light flickers from amber to green and everything turns on at the same time. Then you see an image about 6-7 seconds later. My secondary monitor, however, doesn't always do this. Instead, I see the light change from amber to green but I don't hear a relay click until about a second later. When the relay clicks then I see the power light, which is green right now, flicker and then I hear the tube fire up. When this happens when the monitor is cold it takes at least 60 seconds before I finally see an image. What is possibly causing this? Should I worry about it?
With my P1110 for instance, if it's been really cold (i've been out all day today), black appears slightly green at startup and hence the picture appears brighter. This normalizes in less than 10 minutes - that's lots better than having brightness drift for 2 hours.
For the second monitor, you may have a problem with the power supply but it's likely something simple like a cold solder joint. I'd try and touch up the soldering, specifically all the joints around the CRT neck, all big semiconductors and relays.
Since you will have to up G2 quite a bit after eliminating the drift correct circuit, make sure you adjust it so optimal picture is at 50% brightness or below. I've talked about it sometime earlier, these monitors are wired to automatically lower the contrast when you up the brightness past 50%, to keep focus in check. Trouble is, this also shifts the color balance a bit, which is annoying. Better avoid it by setting G2 so that picture is bright enough before you reach 50% brightness in the menu.
Also i'm not sure anyone has mentioned this before: Always remove the ECS cable from the monitor when you're done with WinDAS. Keeping it in causes interference with the 5v rail which shows as slight wobbles in horizontal size.
Still works, but you can see jittering in text and small lines.
It's been disconnected for a year now.. Man it's been a long time since I switched to an LCD. Damn thing is still on my desk because I can't even safely lift it off. (Was for running classic games on, but I can't look at CRTs anymore, too much eye damage done, strain is too much now.)
Now if you'll excuse me, i'll be back to my game... Hey look, the picture's so clear i can see the scanlines!
I have just opened up the monitor. I'm in the process of removing the metal shields.
http://www.mojoimage.com/free-image-hosting-view-09.php?id=6767IMG_20120126_180600.jpg
Another problem is that if it is colder in the room then the monitor takes about a minute to warm up and show picture. On the other hand, if the room temperature is 36 degrees C, the monitor displays picture almost immediately.
Anyone has the same problem or knows what can be wrong with the monitor?
The monitor used to be too bright and have a green image, but I reduced the brightness with WinDAS and corrected the color using the on-screen menu. WinDAS has a way of adjusting the color more precisely, but that requires a colorimeter which I do not have.
@ theothernewguy:
http://www.eserviceinfo.com/downloadsm/3282/Sony_CPD-4402.html
http://www.eserviceinfo.com/downloadsm/3283/Sony_CPD-4402.html
http://www.eserviceinfo.com/downloadsm/3284/Sony_CPD-4402.html
Interestingly enough, your monitor seems to NOT have the drift correct circuit... but i'd look for it, since the symptoms are exactly the same as my P1110.
@ sintz: That's what we've been doing all this while. :p
1. Abnormal G2 voltage, usually 100V~ higher than its original spec at 522V. The G2 voltage can be bring down by modifying relevant value with WINDAS, and after the tweaking, overall brightness level can indeed be lowered. The cause of this phenomenon is still unclear – some people believe it’s caused by EEPROM data corruption, which I seriously doubt: data corruption in ROM is usually random, so why it’s always the G2 value suffer the loss?
2. The picture is over-bright, a little greenish on black at startup and after a while (15-20 minutes or so) the picture become darker, its color more saturated and able to maintain correct black & white balance. Some people claim that brings down G2 back to normal will cure everything, but it’s not true. Although after proper adjustment (for my unit, the G2 value was tweaked from 157 to 126, set at 30 in OSD for brightness) the monitor’s brightness level may be in normal range even the moment after a cold start, but the tendency (darker and deeper over time) is still the same, while the G2 is actually stable all the time. I think this is caused by some inferior semiconductor component, IC403 or IC406 perhaps, the characteristic of which will drift as temperature arises. Since I don’t have any replacement parts, I cannot confirm.
3. No picture, filament will not be light up after power button is pushed. This is often caused by a faulty BA00AST IC, which is an adjustable linear voltage regulator similar to 7805 and provides power for the heater.
By the way, P1110 (G500, and even FW900) lacks the mighty GEM (Graphic Enhance Mode) button featured in earlier Sony computer monitors like 220GS/D1025TM, which limits its effectiveness in movie playback / gaming. The button is replaced by an Auto-Center button, which is almost useless as everyone knows. Sony engineers are not fools, so I guess there must be technical difficulties behind this change. Despite all these problems, P1110 is still a decent monitor, although it’s far from perfect.
As for why it increases over time, i think it's a firmware bug not EEPROM corruption.
And thanks for mentioning the "proper" G2 value, i hadn't known it until now. If it's mentioned in the service manual i'd like you to point me to it, coz i didn't find it. With all adjustments complete i've arrived at somewhere around this value too for mine, so clearly i must be doing right. :) I found a fix for that by disabling the "drift correct" circuit, see above. It still takes around 10 minutes to fully warm up, but it's tons better than it was before. Mine used to take 2 hours to settle! And it required a lower than normal G2 voltage (430v) for proper brightness range, even when it did settle down.
I own a Formac ProNitron 21/750 (same model as dell P1110 - chassis GDM5403)
After several tweaks with win das past years, it seems to be quite stable, and really crystal clear.
I'm very interested by Th3_uN1Qu3 mods on IC406 : maybe i could try to bypass the transistor which causes problems.
I have had another problem with this monitor last year, which was fixed :
The brightness was not stable, and i was wondering if the monitor was ready to go to the trash...
But, in fact, the solution was very simple :
after resoldered all the connections beetween N-board and D-board, it was OK.
I suspect many problems could be fixed by carrefully resolder all the connections.
I'll also point out that all of the resistor mods people have done until now are wrong - because they have addressed the effect not the cause. Those resistors all checked fine on my P1110 which came with a really bad case of overbrightness (so clearly, they do not need to be replaced), and by changing the resistors in the divider for the opamp feedback loop the G2 voltage will still be prone to drifting over time because it's still wired to the MCU. Now, if you cut the MCU line and place a multiturn pot instead, you have addressed the cause and it will never drift again regardless of what the MCU is trying to do. I'll elaborate on that once i perform the mod on my own P1110.
IMO, the circuitry in these monitors is far too complicated, they could have done it a lot easier. Because fact is, the tube is still going to age and require alignment every few years - all they did was make it harder to adjust. Like the stupid "lowering contrast when increasing brightness past 50" thing. I want my trimpots back damn it! If i have the time i'll be rolling my own MCU to take care of the critical functions. It won't be easy but it's doable. I suspect that some of these mods can be done at firmware level and patched in via WinDAS, but with no datasheet on the original micro this wouldn't be easy. Rolling my own seems like a far better idea. In fact, if it were me, i'd just replace the whole thing by a bunch of trimpots, but not everyone likes the idea of getting inside their monitor all the time.
IMO, they wanted to make a monitor which is immediately usable when switching ON, by placing complex circuits for controlling brightness.
In the old times, i've had monitors which tends to be very dark when switching on, and takes 10~20 minutes to warm up.
With the P1110, it's the opposite. :D
Then the mod would be like this:
Note that any value between 1k and 500k will work for the trimpot - i just happen to have a ton of 100k ones lying around. The higher values also are more prone to interference, so i'd stick to 100k or under. It is not necessary to actually remove the deleted parts from the board, just find a way to cut the trace leading to the opamp and drop your trimpot on there.
What i do not know yet is whether the G2 value set by the MCU affects others too, like contrast or colors. Well, only one way to find out i guess. :) I'll be performing the mod tomorrow. However, i want to take it one step further. As you see, the G2 voltage is controlled by an opamp. That gives extraordinary flexibility to the adjustment - you can control it by basically anything. Now, i'm about to blow your socks off. Tube takes time to heat, correct? Brightness drifts until tube temperature settles. G2 voltage directly affects brightness. Now, what if we put a temperature sensor on the tube neck, and use that to transparently adjust G2, thus eliminating the brightness drift entirely? :D Of course, a trimpot will still be there to set the base level, but the temperature sensor should be able to keep things in check once the base level is correct. Now it's time to stick a temperature probe to the tube neck and do some data logging.
I'm curious to know the result.
And, like you said, I hope the MCU does not control other parameters (contrast ? white balance ?)
Hang on, there's some cool data coming up.
Edit: Here we go. I plotted tube temperature vs time, measurements taken every minute. The probe was stuck on the top of the neck, right under the first metal ring, the one that holds the purity magnets in place. Ambient temperature was 22C. As you can see, past 15 minutes the temperature rise slowed down, and it stopped rising entirely past 30 minutes. Visual feedback confirmed that, after 15 minutes the brightness drift per minute became unnoticeable, and past 30 minutes the picture is completely stable.
Of course the temperatures are relative, if the ambient temp were different the tube temp would be different too, but this proves that with the drift correct circuit removed, brightness drift is due to the tube and not any other component. It also shows why the drift correct circuit didn't work: Tube temperature vs time is nonlinear, whereas that transistor, not being in contact with the tube directly, provided a linear thermal compensation, which isn't what we need.
As far as i know G2 voltage vs black level is a linear relationship, provided we stay out of cutoff/saturation. Since the tube worked just fine with G2 a whole hundred volts lower than nominal before removing the drift correct circuit (that messed with the cathode voltages), and that hundred volts meant a significant change in brightness (from "barely visible" to "normal") we have a decent range to play with. By making G2 voltage a function of tube temperature i believe we can eliminate brightness drift completely, reducing the "warmup time" from 15-20 minutes to 2 minutes or less.
Time to stick a thermistor on the tube neck and see what happens.
Especially some of the big transistors on the D-board, just near the tube.
Two years ago, I covered almost all the vents with paper and tape so that the temperature inside the housing is higher. Especially in the winter because my house is not warm enough... :D
That worked : black on screen becomes really pure black, with this trick.
But just for a time... after that i decided to use win das.
But if we display a dark image (a screen saver, for example), after a few minutes, the black drift back to dark gray.
It seems that some component (maybe the tube ?) cools when displaying a dark image, and warms when displaying a bright one.
Once it's warmed up, as long as the heater remains on the tube temperature remains constant, regardless of the brightness level of the picture, so you can take the tube out of this equation. Bypass the drift control transistor and see what that gives you.
I've done a bit of math and it turns out we can get pretty good precision from simple cheap NTC thermistors over a temperature range of +/-25C, using a parallel precision resistor to linearize the NTC. This should be enough for the typical operating range of the tube, and will allow for a warmup time of 5 minutes, maybe even shorter. Now all that needs to be done is some measurements to determine the actual values needed for the circuit.
Anyway, the circuit is so simple i can hardly believe nobody's done it before (searching for "cathode ray tube thermal compensation" brings up a few patents about projectors, two about CRT mask design, but nothing like i described above). I suspect however that the severity of this brightness drift varies with the age of the tube (since it didn't do it when it was brand new) so it's likely an adjustment that will need to be touched up once an year or so. More trimpots for you! :p