Hi to everybody;
this is my first thread, after a long time of zapping through the forum.
This is what happened: I was trying to optimize static magnetic correction of my 8500; so, after centering raster, making flare and astigmatism, I checked convergence and scan yoke. But they were joined together by hot glue and so I was not able to achive correct correction. Due to a misunderstanding of the real aspect of "hot glue" - I thought it was the gray piece soldering copper windings - I broke windings of the scan yoke of the green tube . Tryed to power on the projector, but, even if it sounds normal, I have no image on each tube: they remain off.
I have completly disabled electric connection of the green tube with each board, removed HV cable from the splitter and removed the green board, but the tubes remain off.
What do you think about? what else can I try?

Thanks in advance

Hello

The system is designed to shut down without all three yokes in good working order. PM me if you want to order a scan yoke.

The system is designed to shut down without all three yokes in good working order. PM me if you want to order a scan yoke.


Thank you very much, Tim. I was afraid I made an unrecoverable damage to boards or tubes...
I live in Italy, so I'll try to find the scan yoke in EU, just to evite long custom stops that every time happens importing stuffs from outside EU. Anyway if I won't find one, I'll buy from you.
More, I'd like to thank persons like you and Curt who shared their knowledges and passion with people on the web, manteining alive a wonderful, mature, reliable and now affordable technology like CRT videoprojection.

I apologize for my imperfect English, but hope you understand what I mean.

Thank you, very much indeed

Hello

The system is designed to shut down without all three yokes in good working order.


Oh, yeah.

If it were to operate without either of the sweep yokes/color - horizontal or vertical or both - it would either give you a horizontal line, a vertical line, or a dot in the middle.

The lines would be at least 480 times more powerful than they should be, and the dot would be more than a thousand times more powerful.

The result would be instant vaporization of all phosphors within the areas of either the lines or the dot, within seconds of turn-on. If it were the horizontal sweep, HU'd in parallel, that color ONLY would be affected. If it were the vertical sweep, which is hooked up in series, all 3 guns would be affected.

Whenever you go inside a sophisticated instrument like this without the proper experience and/or training, you take the life of that instrument in your hands.

For now you have dodged the bullet of having ruined only your sweep yoke, which takes no setup to replace. If not for this failsafe, your CRTs would have been at risk as well. And they DO take re-setup, once installed, along with not being inexpensive themselves.


Be afraid. Be very afraid...


Mr Bob

Hi Mr Bob,
believe me, I learned the lesson..
Just a question more: is a scan yoke from 9500 tube compatible with my 8" tube.

Thanks

Yes it will work, but the pix will be a bit narrower/wider (I can't remember which) as the yokes are SLIGHTLY different.

I disagree with Mr Bob though, you will need to do a complete setup of the astig/yoke, etc when you replace the yoke, as you're taking everything off the neck of the tube to get at the yoke.

Hi Mr Bob,
believe me, I learned the lesson..
Just a question more: is a scan yoke from 9500 tube compatible with my 8" tube.

Thanks

Hello

Yokes need to be matched, identical, or the width will be wrong.

Guys!

The fine copper windings in the yoke are easily damaged, especially when sealed to the tube glass by hot glue.

http://www.etechvideo.com/images/Tip9/Tip9_02.jpg

Those needing Marquees retubed should arrange to ship their units here for servicing and any desired mods.

I disagree with Mr Bob though, you will need to do a complete setup of the astig/yoke, etc when you replace the yoke, as you're taking everything off the neck of the tube to get at the yoke.

Whenever I replace a sweep yoke, I always very carefully mark EXACTLY where it was on the neck, plus EXACTLY where everything else was - the centering magnets if separate, the astigmatism magnet rings set (fully immobilized of course), the convergence yoke if separate - and when I put it back on, all those go back EXACTLY where they were before, so that their magnetic fields hit EXACTLY where they are supposed to, inside the tube neck.

As a result, I usually don't have to do any revamping of all those critical alignments. After all, an alignment saved is an alignment earned. In calibration time, possibly referencing, attention and concentration. And definitely in squinting...

Of course this has always been with CRT RPTVs, have never had to it with ceiling pjs. Things could be totally different with these higher-echelon beasts...

;)

Mr Bob

I've only done this once, but I would think that at a minimum the focus, flare, and astig would have to be adjusted for each specific tube, since no two cathodes will emit exactly the same and be mounted in the exact same position within every tube. Is that not the case?

I've only done this once, but I would think that at a minimum the focus, flare, and astig would have to be adjusted for each specific tube, since no two cathodes will emit exactly the same and be mounted in the exact same position within every tube. Is that not the case?


We're not talking about regunning a CRT pj, here. We're only talking about replacing a broken sweep yoke, mounted on an existing CRT.


Mr Bob

Well I'd redo the whole astig adjustment, but that's just me.

Well I'd redo the whole astig adjustment, but that's just me.

Astig is something that can always be checked out for efficacy before changing anything. I would do that first - if needed, I'd do a complete realignment too!

Being able to check things out without actually changing them was why I came up with the Cantilever Technique years ago, for the tightest possible optical focusing of your lenses.


Mr Bob

Of course this has always been with CRT RPTVs, have never had to it with ceiling pjs. Things could be totally different with these higher-echelon beasts...

;)

Mr Bob

OK, for a while there you had me a bit confused, but things are now making more sense with marking things down and not having to re-do everything once you swap out a yoke.

Your experience is RPTV's - correct?

OK, for a while there you had me a bit confused, but things are now making more sense with marking things down and not having to re-do everything once you swap out a yoke.

Your experience is RPTV's - correct?


My experience with swapping out defective sweep yokes is with RPTV, right. Have not had occasion to need to do that with ceiling pjs yet.

Most of my repair experience with CRT tech is with RPTV, but I have had lots of experience with repair of CRT triple gun projectors as well. I am one of the home field techs/calibrators for Runco, and have been for years. I have repaired many brands of front pj over the years, including some little known ones like JBL. And more well known ones like Vidikron.

My calibration experience with CRT tech is with both RPTV and FPTV - also known as ceiling/floor mount projectors. Or table mount projectors. And DVs.

My calibration experience is vast with all these CRT formats. My repair experience is substantial also, just not as vast as my calibration experience.


Mr Bob

You could never fix the JBL 6810s or 6850s. You can only throw them out..;)

You could never fix the JBL 6810s or 6850s. You can only throw them out..;)

I have. Don't know if it was either of those models, but I have repaired 2 JBL pjs. One needed a no longer available low voltage transformer for the passive power supply, and another was a huge cold solder joint on one of the legs of its flyback.

The Barco Data 800 sitting up on its side in my garage had a cold solder joint problem too, which was causing shutdown. It was in the -18v power supply.

Once that was remedied, she fired right up, and makes dazzling HD now.


Mr Bob

MR Bob, my post was somewhat tongue in cheek. Did you know that Philips made those sets for JBL? They were notorious for bad solder joints where the connections were made through the board from top to bottom. YOu had to resolder all joints on the top and the bottom of the board, and even then who knows how much longer it would last? I did see one set that had tube wear, so yes, the odd one did last a long time, but the three or so I've had through here I ended up throwing out.

The later Harman projectors weren't too much better.

MR Bob, my post was somewhat tongue in cheek. Did you know that Philips made those sets for JBL? They were notorious for bad solder joints where the connections were made through the board from top to bottom. YOu had to resolder all joints on the top and the bottom of the board, and even then who knows how much longer it would last? I did see one set that had tube wear, so yes, the odd one did last a long time, but the three or so I've had through here I ended up throwing out.

The later Harman projectors weren't too much better.


Gotcha. We used to find the same thing on the Concord car stereos, with dual-sided boards.


Just had a chance to experience Cliff's double-stack G90 system, here in Indiana. Don't have time for a review right now, since the plane leaves Midway at 5:40pm and I want to TRY to see some of Chicago before I leave - yesterday it was too late before I was freed up at the last place I was staying at, and by that time of the day it was recommended that I not even try to navigate Chicago. that all my time would be lost in the commute.

Let's just say for now that I was completely blown away last night, with Cliff's demos. This morning he played me the invasion scene from Matrix II, and I was blown away all over again!

More later, after I am home again -


Mr Bob