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My Master Monitor image is skewed! Any advice?


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#1 Beau Chaput

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Posted 05 January 2006 - 01:53 PM

Happy New Year to all, hope 2006 is productive for us all.

I have recently noticed that the image on my master series 5 inch monitor is skewed! The image and the frameline is tilted down on the left. I had thought it was the top frameline only but after a minute I realized its the whole image. Does anyone know what may have caused this or what might be done to fix it. Thanks in advance for any input into this matter. Regards, Beau
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#2 Norbert von der Heidt

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Posted 05 January 2006 - 05:21 PM

Happy New Year to all, hope 2006 is productive for us all.

I have recently noticed that the image on my master series 5 inch monitor is skewed! The image and the frameline is tilted down on the left. I had thought it was the top frameline only but after a minute I realized its the whole image. Does anyone know what may have caused this or what might be done to fix it. Thanks in advance for any input into this matter. Regards, Beau



Hi Beau

It sounds like a simple matter of a loose deflection yoke on the crt. The monitor has either been knocked or during a maintenance wasn't tightened up enough. If you are mechanically inclined it isn't hard to fix.
Turn off power and remove the cover from the monitor. Around the crt at the point where the tube flares out there will be a plastic assembly with a lot of fine copper wires looped symetrically together in 4 groups (I think) around the assembly. At the opposite end from the wires should be a yoke clamp with a locking screw, this is what more than likely needs to be re-tightened.
Here is the tricky part. Loosen off the screw enough so that the yoke can be easily rotated. Feed a video input and power to the monitor. Keep fingers away from any components and fire it up. Now, being very careful not to touch anything else but the plastic yoke, rotate the assembly until it is back horizontal again. Be sure that the yoke assembly hasn't moved up or down on the tube's longitudinal Z axis as this can effect everything else you don't want it to e.g. focus, frame size, etc. Re-tighten the lock screw and check for horizontal again as this can sometimes shift when locking down. Repeat above till it is correct. Turn off power and put cover back on. Voila, c'est tout fini.

Hope this is a help. ;)
Cheers
Norbert
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#3 Eric Young

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Posted 06 January 2006 - 03:57 PM

Norbert is correct, but didn't specifically mention there are very high voltages (from 100s of volts on the big capacitors, to 1000s of volts in the EHT areas) in a CRT monitor!! Now most modern CRT monitors are designed to rapidly discharge these when switched off, so in theory you should be fine if you remember to do this. However, some monitors have electronic "Standby" power switches rather than true hardware power switches, so just pressing the on/off switch isn't guaranteed to cut ALL power when you are rummaging around the insides with the cover off. The only way to be sure would be to remove the power source completely (the battery or power cable).

During the trial and error cycle of switching it off, waiting for the EHT to discharge, removing the power source, loosening and adjusting the yoke, retightening, switching it on, checking the picture, switching it off, waiting for the EHT to discharge, removing the power source, loosening and adjusting the yoke, retightening...etc, it is very easy to forget to remove the power source at some point, resulting in potential danger. It's happened to me repairing a studio monitor, and it wasn't pleasant, but I lived to tell the tale!

I really would NOT recommend doing this unless you are very sure of what you are doing (or preferably a qualified electronic engineer like myself!), and are fully aware of the potential dangers. At the very least, don't work on it alone. It would be sensible to have someone else present who knows how to treat someone who gets an electrical shock. (The biggest risk is heart stoppage if electricity goes across the chest - so using only one hand to adjust the yoke and not touching anything with the other will reduce this particular risk somewhat)

Regards
Eric
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#4 Beau Chaput

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Posted 07 January 2006 - 04:15 AM

Geez, thanks alot to both you guys for your time I really do appreciate it. I am going to get some help and take it really easy. I have a healthy respect for any electricity so I won't mess around. I will post and update on how it goes. It's good to hear that it isn't something unreversable, and again thanks for your time and your knowledge. Hope I have good news soon! Beau
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#5 Norbert von der Heidt

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Posted 07 January 2006 - 08:42 AM

Norbert is correct, but didn't specifically mention there are very high voltages (from 100s of volts on the big capacitors, to 1000s of volts in the EHT areas) in a CRT monitor!! Now most modern CRT monitors are designed to rapidly discharge these when switched off, so in theory you should be fine if you remember to do this. However, some monitors have electronic "Standby" power switches rather than true hardware power switches, so just pressing the on/off switch isn't guaranteed to cut ALL power when you are rummaging around the insides with the cover off. The only way to be sure would be to remove the power source completely (the battery or power cable).

During the trial and error cycle of switching it off, waiting for the EHT to discharge, removing the power source, loosening and adjusting the yoke, retightening, switching it on, checking the picture, switching it off, waiting for the EHT to discharge, removing the power source, loosening and adjusting the yoke, retightening...etc, it is very easy to forget to remove the power source at some point, resulting in potential danger. It's happened to me repairing a studio monitor, and it wasn't pleasant, but I lived to tell the tale!

I really would NOT recommend doing this unless you are very sure of what you are doing (or preferably a qualified electronic engineer like myself!), and are fully aware of the potential dangers. At the very least, don't work on it alone. It would be sensible to have someone else present who knows how to treat someone who gets an electrical shock. (The biggest risk is heart stoppage if electricity goes across the chest - so using only one hand to adjust the yoke and not touching anything with the other will reduce this particular risk somewhat)

Regards
Eric



Hi Eric
Oops, I forgot! Good that you added that very important fact regarding the high voltages!! :o
I'm so use to poking around in the guts of cameras, VTRs, etc. for over twenty five years and yes, I have been thrown across the room by the 27k HV output, I just assume everyone knows to be extremely careful. I now use only insulated tools whenever I work on live gear.

Cheers
Norbert B)
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#6 PeterAbraham

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Posted 07 January 2006 - 06:55 PM

Good advice, fellahs. Another fine reason to always carry a coupla pair of latex or better yet Nitrile gloves in the kit. The good purple Nitrile gloves have textured fingertips and are non-conductive. They also fit like a glove. :D

It's an excellent thing to learn how to do, but I readily agree it's dangerous stuff. Find a t.v. repair shop ( yeah, right......these days?....... ) and get the tech to show you how to loosen and align the yoke. Its mighty helpful to have some lines being generated so you have perfect verticals to make use of.

Peter Abraham
New York
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#7 Eric Young

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Posted 10 January 2006 - 11:32 AM

Good advice, fellahs. Another fine reason to always carry a coupla pair of latex or better yet Nitrile gloves in the kit. The good purple Nitrile gloves have textured fingertips and are non-conductive. They also fit like a glove. :D

Peter Abraham
New York


Ha ha! :D Was going to suggest washing up gloves because their readily available and protect the forearms too - but thought that would be too much like encouraging Beau to "have a go"! Also, washing up gloves obviously aren't designed to protect against very high voltages, so there's no guarantee they are sufficiently insulating.

I still strongly advise against doing it yourself, Beau. So glad to hear you are going to get qualified help!

Eric
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#8 Marc_Abernathy

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Posted 10 January 2006 - 02:14 PM

dont put too much faith in those gloves.. they can get tiny pin holes in them and can still cause electrocution. it doesnt take much for electricity to find a path to ground...
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#9 Beau Chaput

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Posted 04 May 2006 - 01:35 PM

thanks all for your help got it fixed kinda

It has been awhile but just wanted to say I messed with my monitor for several days and am still alive although I was very very careful thanks to you guys. John Myers and myself spent a week of lunches on the truck working on it. Ended up adding magnets to a few spots with silicone and that did the trick. Got it about %80 percent better. I apprectiate all the posts awhile back, thanks again, Beau Chaput
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#10 RobinThwaites

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Posted 05 May 2006 - 03:55 AM

Hi Guys
One further thing is that some of those monitors use small trim magnets which are glued to the yoke or CRT to adjust linearity. These sometimes fall off and need to be glued back on so check for loose magnets in the monitor before anything else.
Robin
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