Hello!
I know that lately I am bothering you a bit too much with all my hardware "problems", sorry, this is what happens when you buy stuff from e-bay from time to time :picard2: Luckily, I did not experience any serious issues, just minor things that needed to be adjusted.
Now is time for the screen. I received it a few days ago along with a working 464 Plus and I am actually very happy with it. I was carefully cleaning the unit and it works very well. Sound is good, color is bright and image is crisp. However, there is a BUT, and in this case is the geometry of the image. It turns out that the image is apparently slightly rotated counterclockwise. However, if you check more carefully, the "rotation" mostly affects the top right corner. So, some of the electrons are actually traveling a bit longer than they should. I have a big speaker next to the screen, and the first thing I tried was to remove it, but it did not help. Now I remember that I also have a subwoofer below table that I did not touch, I will try this today. But, in any case, assuming that it is the screen itself, could you tell me if there is a proper way to adjust the geometry a little bit? or, in case I need to check something in particular inside could you point me to it? I have quite a lot of experience with audio amplifiers, but not with CRTs, I never liked to mess with them so much for obvious reasons :D
This morning I took a picture for you to see. If you check carefully, the image is a bit bent toward the upper right corner (sorry for all the stuff that appears around)
[attachimg=1]
Any help be much appreciated!!
I'm not sure if there is anything in the monitor to adjust that (I think not, but if there is, there's a good change it should be indicated in the service manual). While cleaning it up, did you moved somehow the internal speakers? But from the picture, I think it is Prophet's nanosuit trying to absorb the electron beam :)
Hahahaha, no, I did not move the magnets. Maybe it is actually Prophet, who knows! Checking the service manual of the other models of Amstrad screens I found that there are some knobs inside that could be probably used, but I never tried to adjust anything like that. That is why I am curious to see is somebody did it in before :)
A little "rule of thumb" I learnt back when I was fixing TVs regularly: Only symetrical problems (such as pin-cushioning) can be fixed with adjustments, if it's non-symetrical it's usually some component that's failing or has failed.
In your case it could be a convergence problem (colours not lining up properly) or there's a similar issue where the top left border gets slightly dragged to the left (there's a name for this, which I can't remember at the moment). Both of these issues can be due to several things, but in a device this old, my first bet would be capacitors dried out and dying.
If you can display a squared grid on the screen and post a picture of that, it would be easier to analyse the problem.
Bryce.
Thank you Bryce! I will display the square grid then :) Replacing the capacitors should not be more difficult than usual if this is necessary. I will just try not to end like a fried chicken :picard: . One thing I noticed is that there is not convergence problem as such, all the colors are displayed very properly (at least judging by eye), is just the slight deformation.
It's difficult to tell from the picture you posted, but I think the whole picture is equally rotated. If this is the case, then it's just an adjustment. However, the point of adjustment is very near the scary voltages, so you need to be careful if you do this. The process is even described in the CM14 service manual.
Bryce.
The picture is a bit rotated as a whole, yes. I will display a grid tonight and then we can check if, besides the general rotation there is something else. I am a bit scare to do the adjustment but oh well...
Don't be pussy, just open it and try tuning every yellow screw till you find right and make it perfect.
You will be proud of yourself.
Big mirror will be helpfull. :)
From the picture you posted, it looks like the defection yoke has moved slightly. It is held in position with the aid of three wedges. See section 3-4 Dynamic Convergence on page 44 of the service manual (Service Manual Amstrad Plus).
Mark
I made a little set of tests to better diagnose the problem, but I think that the most informative one is this grid.
[attachimg=1]
It really seems that is a problem of general rotation, yes. I also prepared some more texts that display color bars and the convergence is, at least by eye, perfect. This screen is super-bright too, I have to keep the brightness at around 75%, otherwise is just too much for me :)
Quote from: ZbyniuR on 22:59, 17 March 16
Don't be pussy, just open it and try tuning every yellow screw till you find right and make it perfect.
You will be proud of yourself.
Big mirror will be helpfull. :)
The rotation isn't done by any of those "yellow screws" you speak of. Re-aligning the rotation involves loosening the deflection coil and turning it slightly (as 1024MAK mentioned). The screen with grid looks like your main problem is just rotation. It's relatively easy to do, but be extremely careful when doing anything inside a CRT that's turned on!
There may be a tiny bit of barrel distortion too, but that might just be the curve of the screen.
Bryce.
Thank you Bryce!
I do not know if I will adjust it or live it the slight rotation. I mean, I know that it is not that difficult in theory but on the other hand I do not like the idea of messing with it at all, particularly when it is on. Although I have the manual I lack a step by step tutorial and I am not familiar with CRT screens. On the bright side, I think that the barrel thingy I is just the curvature of the screen, nothing to worry about. I am sure that if I managed to find one of those technicians that used to repair TVs at home in the past it would be very easy for him to solve this.
I can understand your apprehension. Here's a step by step of what needs to be done anyway. This picture isn't from a CM14, but similar enough that everything will look pretty identical if you open your CM14.
So... We're looking at the rear end of a CRT. The green connector to the left will have a small PCB connected to it, kind of floating in the air, probably with 6 or 8 wires coming from it. Don't touch this PCB, it probably won't kill you, but it will hurt like hell. The deflection coil is the big copper windings you can see in the middle of the red circle. They are mounted on that big piece of white plastic. So what do you need to do? This coil (and it's plastic mounting) has rotated very slightly, which is why your picture has also rotated. It's held in place with rubber wedges at the screen end and usually just a single screw / pipe-clamp at the other end. Firstly, it may already be loose, so gently check whether you can rotate it back to the correct position before doing anything. If it doesn't move, you'll need to slightly loosen the screw I've circled in purple and then adjust it as required. When you're happy with the rotation of the picture, you just need to tighten the screw again. Be careful not to misalign the coil again when tightening the screw. DON'T TIGHTEN THE SCREW TOO MUCH OR THE TUBE WILL CRACK!!! Just enough to hold the coil in place. If you use a pair of insulated gloves (even kitchen "washing-up gloves" are enough) you can pretty much touch anything in that area. The only really scary bit that you need to avoid is a big red wire that goes to what looks like a plunger on the back of the screen. Don't go near this, even with the gloves. That's the HT line and carries several thousand volts, even when the TV is turned off and unplugged!
Bryce.
Thank you so much, Bryce! Well, with this tutorial I think that I will be able to give it a try! :D I understand that I do all the adjustments with the screen disconnected and then I check turning it on if everything is OK right? That way, if something goes wrong, "only" the capacitors will discharge :-X . We should have proper gloves for this in the lab, we do not use CRTs but I am constantly working with electrophoresis chambers and I run my gels at 200V and 1A most of the time. Since this is enough to give you quite a shock and our chambers are physically open (with the liquid easily splashing when you move them) we have special disposable gloves. I will take a few with me today :)
As long as the gloves are insulated and thick enough that a sharp point can't pierce them you are fine.
Regarding when to power it. I would recommend the following order: With the monitor turned off, open it up and position it where you can easily move around it and have good access to the areas of the tube you need. Check whether the coil moves, if not loosen the screw. Now power up the monitor and adjust the coil to the correct position (with gloves on). Tighten the screw again and unplug the monitor. Now you can close the case again and enjoy a straightened picture :)
200V (DC I presume) 1A - This is enough to send you to the fairies!
Bryce.
Edit: You may find that there are two screws on the neck of the tube. If so, you only need to loosen the one closest to the coil, the other screw shouldn't be touched.
Thank you Bryce!! So, yes, our power supplies deliver those 200V and 1A when we are working with them in a ordinary way. I some cases, with huge chambers, I have set them to 400V and 2.5 A. We need to do this in a cold room, of course, otherwise the chambers tend to melt. BTW, the wires that conduct the electricity in the chambers are made of platinum and I recently scrapped one. If you need some extra high quality conductive wire, I have a some here. It is crazily good, we use these wires immersed in solutions with high salt concentration and they never ever get rusty :D
About the screen, I will open it and put it back in the little plastic stand I use. It seems very appropriate because I have plenty of space around to maneuver :)
Let us know how it goes.
Bryce.
Some scary stuff in this thread. I have a couple of CRT I need to adjust by opening them, but I'm deathly afraid of doing so.
I'm considering buying these gloves Insulated 12kv High Voltage Electrical Insulating Gloves For Electricians HK | (http://www.ebay.co.uk/itm/Insulated-12kv-High-Voltage-Electrical-Insulating-Gloves-For-Electricians-HK-/281892491693), but I'm not sure I'd be even able to move my fingers in them!
Related to the topic: the 240p test suite is a great set of tools to fine tune a CRT and measure metrics like display / input lag, etc. 240p test suite - XRGB wiki (http://junkerhq.net/xrgb/index.php/240p_test_suite). You need one of the supported consoles (so many, the Wii being the best due to 240p/480i/480p support), but it's open source so maybe it can be ported to the CPC too?
Quote from: Bryce on 15:20, 18 March 16
Let us know how it goes.
Bryce.
Sure, I will keep you all up to date :) . One question, what´s the best part to grab and rotate? The white plastic? The black area between the copper coils? I guess that the white plastic, close to the rubber, is the best option, but just in case :)
About the tests, the static ones are easy to port to the CPC, or they should be. In my case I just followed a dirty approach: using the visualizer I modified to check the graphics of our adventure I prepared some graphs in the PC and I converted them to SCR format. This works reasonably well.
The way I do it: Don't loosen the screw much, so that it's still relatively difficult to turn the coil. Then set a screwdriver on one of the plastic ridges (there's usually several) and gently tap the top of the screwdriver with another screwdriver. It's much easier to fine tune it this way.
Bryce.
Gesendet von meinem Motorola DynaTEC 8000X mit Tapatalk 2.
Thank you!
I am at it right now! It is not extremely difficult, indeed, but tedious. It is easy to rotate it too little or too much and it tends to go back to the original position :) However, the adjustment works! I hope to have it finished later today! :)
Of course, now I moved the magnets adjusting the other thing... very nice to make all the colors converge again, Jesus :picard2:
I found that the technician that did the adjustment 30 years ago, or so, marked all the correct positions at that time, Good bless that guy, everything is back to the correct place :-\ The pics I took helped as well :-X
Edit: Now I also found that I had not moved the magnets, it was, of course, the iron of the screwdriver when close to the electron beam causing the problem and magnetizing the screen :picard:
OK, the image is straight now :) The only problem is that, because of me coming and going with the screwdriver now the top right corner is magnetized and I see a with of a yellow staining in that region. Maybe I will have to degauss the screen, although it should go away over time, right?
Edit again: I demagnetized it with a small magnet, it worked wonders :D
Adjusting the V-size now... that was completely wrong as well :-X
Keep at it.
You'll get there one day.
Never give up.
It is actually ready now :D
You seem to be really enjoying yourself there :D I suppose it's interesting as a "non-electronics person" to see how all the different magnets and coils effect the picture in different ways. As long as you are careful it's not difficult. Glad you were able to tune the picture to exaactly how you want it.
Yup, I forgot to mention in my step-by-step, that the metal of the screwdriver effects the adjustment. I use a ceramic screwdriver for stuff like this, but it's easy to compensate for the effect of a normal screwdriver, so there's no need to go and buy a special one just for a once off job.
Bryce.
It was cool but stressing, at least at the beginning :-X But now everything is much better, it actually looks very nice. There are two things that are still there, though. The first is certain amount of dirt I caused with my screwdriver. I removed most of it, but some remains in the upper right corner. I can make it disappear if I put a small neodymium magnet on top of the screen, but it does not seem a really elegant long term solution. I guess that I should consider to demagnetize it, but I do not have a degaussing coil here and they are a bit expensive :( . When I received the screen that corner was already not completely perfect, but a bit darker than the rest, now it is yellowish. The second is that the screen could benefit of a very very slight correction of the dynamic convergence. This is almost not noticeable and I have seen the corners of almost all CRTs with a little bit of this problem, but still. I will not probably try it, it was there at the beginning and it seems very difficult to correct without messing with another region of the image. I know a guy that did it with an arcade screen using wedges and tape, but it took him a very long time...
Good news! I found that my uncle has at home (in Spain) a huge amount of NOS convergence yoke strips and a set of ceramic screwdrivers that he is not using anymore. So, I will take those with me and see if I manage to obtain a perfect image. In only need to:
a) Demagnetize the bloody thing, because that little tinting in the corner makes me nervous (although I could try to correct everything with a little magnet in the proper place, because that works very well)
b) Adjust a little bit the dynamic convergence with the strips (or at least try)
c) Ideally, I would adjust the H-size by a few pixels as well, but I do not find a resistor to do this, as in the case of the V-size, that was very easy. Is there anything like that or is it necessary to move the yoke? In that case I will let it as it is now.
I was afraid we weren't going to hear back from you :D
H-Size isn't usually adjustable, it's controlled by the LA7800 and some fixed value parts. You can only really change it by changing the frequency of the H-Sync pulses.
Bryce.
It is fine then :). It is just a question of few píxels. In the past this would not be noticeble because of the screen border. Nowadays, in the era of the overscan, is when you see everything :D.
@Gryzor (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1). The first day you try to adjust something you never die, it is only when you feel more condifent that you die electrocuted in the most horrible way :D.
Quote from: ||C|-|E|| on 11:16, 21 March 16c) Ideally, I would adjust the H-size by a few pixels as well, but I do not find a resistor to do this, as in the case of the V-size, that was very easy. Is there anything like that or is it necessary to move the yoke? In that case I will let it as it is now.
For a few pixels, I'd leave it alone. For TV pictures on TVs, the idea is to overscan the image so there are no unused areas. For computer use, you may want a slight border ;-)
Mark
I will let it be then :) . Let´s see if I manage to solve the rest of the things with the convergence strips. I will try to degauss it properly with a coil first (since I do not like the idea of letting a magnetic Pikachu o top of the screen forever) and then I will try with them. I guess that it will take a decent dose of patience, but it is fine. I prefer this approach than trying something risky that would probably screw the things up (like trying to adjust the purity and convergence from scratch completely unscrewing the yoke). With my lack of experience this would a recipe for disaster, so I think that is safer not to mess with the things much. For instance, yesterday I was trying to adjust the purity with the purity magnets but it is very easy to fix the problematic corner just to see that you are creating another issue somewhere else. At the end, I almost let them like they were from factory, but the difference was enough to improve the image.
A few years ago there was workshop in every corner able to do these kind of things, now they are very difficult to find and repairs are very expensive, either that or they tell you to throw the screen away :-X
I know this isn't cpc related but I thought I'd ask here as this thread seems somewhat relevant.
My ntsc snes pushed my picture out to the left on my crt. Foolishly I messed around in the service mode without recording my original settings and now my picture is slightly wavy on either edge of the screen :picard:
Does anyone know which setting I need to adjust? I've spent ages tinkering with it now but none of the settings seem to straighten it up.
By the way, I have no idea why every photo I post ends up upside down :picard:
Quote from: Dr Tiger Ninestein on 15:08, 26 March 16
By the way, I have no idea why every photo I post ends up upside down :picard:
If you're using a phone, just turn it. The Exif data says to turn the picture 180 deg, but the thumbnail does not.
Quote from: gerald on 16:53, 26 March 16
If you're using a phone, just turn it. The Exif data says to turn the picture 180 deg, but the thumbnail does not.
I'm using an iPad. I've tried turning it before but just keep getting the same result
With an iPad, up is with the volume buttons on the top...
Or you can use the picture editer to rotate the picture.
My brain is a bit fuzzy today (so my head has an head ache, so may be wrong here), but do your settings have "pin cushion" in the settings?
Mark
That's not as simple as a pin-cushion problem, there's a definite "wave" in there. Did you mess with some refresh rate setting?
Bryce.
1024MAK. Nope, not that I can see.
Bryce. No I don't think so. Here's a list of the settings in the service menu that I played around with.
Red HWB
B&W HWB
Blue HWB
Green HWB
Ver size
Ver breadth
Pin ampl
Par tilt
V linear
Corn corr
Vcen Ew
V position
H centre
These are the only settings in there, but none of them seem to effect the wave at all. To be honest it's not that noticeable a lot of the time but on certain screens such as when using the super gameboy or when there are straight lines on either side of the screen its obviously really noticeable.
Just a guess here, but I'd bet on it being a conbination of V Breadth and posibbly V Linear.
Bryce.
Ok cheers Bryce. I'll have a play around with those two and see if it makes a difference.
I actually finished solving all the problems with the screen today! The solution was a combination of things that involved fully recapping the board of the monitor and re-adjusting the yoke, but now it looks basically like a new monitor, so I am very happy. I would like to thank Bryce for all the support, without him it would have been completely impossible to tackle this issue and, moreover, he was very patient with me these days that I was bombarding him with private messages (I am truly sorry :picard2: ). I took some pictures if somebody is interested to see them, although I guess that describing the whole process has only limited interest because it is quite dangerous.
I think that because it's a dangerous procedure, better have it well documented.
I've been itching to mark this topic as Solved :D
Quote from: robcfg on 16:09, 03 April 16
I think that because it's a dangerous procedure, better have it well documented.
I can upload some pics and describe what I did then, just bear in mind that I am not an expert in the field at all and definitely not the most qualified person to explain how CRTs work or are repaired :-X
Quote from: ||C|-|E|| on 01:10, 03 April 16
I actually finished solving all the problems with the screen today! The solution was a combination of things that involved fully recapping the board of the monitor and re-adjusting the yoke, but now it looks basically like a new monitor, so I am very happy. I would like to thank Bryce for all the support, without him it would have been completely impossible to tackle this issue and, moreover, he was very patient with me these days that I was bombarding him with private messages (I am truly sorry :picard2: ). I took some pictures if somebody is interested to see them, although I guess that describing the whole process has only limited interest because it is quite dangerous.
I don't mind being bombarded with questions. It's a difficult and dangerous project, especially as a first major electronics project. I'd prefer to be answering lots of questions rather than asking the question "Why doesn't ||C|-|E|| log into the forum any more?"
Really glad that everything went so well.
Bryce.
Quote from: ||C|-|E|| on 02:01, 04 April 16
I am not an expert in the field at all and definitely not the most qualified person to explain how CRTs work or are repaired :-X
I was told of a story yesterday where a Commodore monitor was making a buzzing crackling noise. When opened by a qualified engineer for inspection sparks were flying around the outside of the tube enclosure. The entire thing was a high voltage death trap and was scrapped.
CRT's are dangerous. Just because someone on here has been unwise enough to open theirs, doesn't mean anyone else should be encouraged
Just because you see someone going and playing in the middle of the road, doesn't mean you should. I fear documenting it will encourage idiots to try their hand at a risky procedure.
Lecture over.
Quote from: chinnyhill10 on 10:29, 04 April 16
I was told of a story yesterday where a Commodore monitor was making a buzzing crackling noise. When opened by a qualified engineer for inspection sparks were flying around the outside of the tube enclosure. The entire thing was a high voltage death trap and was scrapped.
CRT's are dangerous. Just because someone on here has been unwise enough to open theirs, doesn't mean anyone else should be encouraged
Just because you see someone going and playing in the middle of the road, doesn't mean you should. I fear documenting it will encourage idiots to try their hand at a risky procedure.
Lecture over.
Very wise words. I would also not be in favour of documenting CRT repairs, for fear that my advice could be filling graveyards.
The story about the flying sparks is real and can actually happen quite often with monitors this old. It happens when the insulation of the HT lead to the CRT (that big red wire with the "suction cup" on the side of the tube) has become brittle and cracked. The high voltage will then jump out of the lead across to the nearest grounded metal (or you if you happen to put yourself in the wrong place). It looks spectacular, but it's extremely dangerous.
Bryce.
I will keep the info for myself then, it seems the most reasonable thing to do :) I would not like my stupidity being contagious and cause trouble, or worse, to someone :picard:
Well done!
As to the pictures ... I'm content with the one where your hair stands on end and smoke is coming out of it. :D