CurtPalme.com Home Theater Forum

[barco_75]

I'm getting ready to follow the procedure listed below and I generaly understand what you are to do. I've read Curts and Guys instructions on tube magnetics mulitple times. However, I've also never done most of this stuff before other than rotate the deflection yoke.

On several instructions, it states "caution" for experienced technicians only, etc. Should I be worried? Any precaustions which are recommended? The instructions don't state if the projector is to be running but I assume that is the only way to determine how the adjustments affect the image. I was planning on using my bare hands and a metal screwdriver to loosen necessary screws (such as those on the deflection yoke) while the projector is running.



Procedure:Tube magnetics:
(3a) Make sure the horizontal deflection coils are hard up against the tube bowl and in an a near upright position.

(3b) Start with the magnetic focus yoke as close to the tube bell as possible. Set center electronic focus to 57 and move magnetic focus yoke back (very slightly) if needed to get sharpest focus in center of screen.

(3c) Set the magnetic focus yoke rotation correctly. Start with completely upright/inline with deflection yoke. This good enough for most.

(3d) Set 2/4 pole magnets correctly to get astig at the center of the screen perfect. To test your astigmatism, do the following: Pull up your genlock pattern select focus in the menu's and one colour at a time turn the focus all the way up and then all the way down, watch for the little lines at the centre and see if they twist violently in a diagonal direction, if they do then your astig is bad!

(3e) Using a grid pattern, rotate deflection yokes until horizontal centerlines coincide. Don't worry about vertical lines being off (convergence will handle this). It's more important to line things up along the horizontal left to right center line.

(3f) For all 3 tubes, do zone astig if your projector has it (this is the outside astig. Center astig's already done with the 2/4 pole magnets). Note: Do not use the Barco internal patterns as the dots are not round.

(3g) For all 3 tubes, Do electronic center focus, then electronic zone focus.

[barco_75]

Most importantly, I don't want to end up like this

[Tim in Phoenix]

Dude

Standard rule; around high voltage keep one hand in your pocket. If you lack a convenient pocket, use your zipper


.

[barco_75]

Thanks Tim, have you adjusted the tube magnetics before? Any other precautions? Is it recommended to use rubber or cloth gloves or is that unnecessary if you are careful and only touch the parts needed for adjustment?

[Tim in Phoenix]

Hello

It is not the yoke signals that pose a lethal hazard, it is 35000 volts jumping from the tube glass. Gloves are not going to help much. That does not happen very often.


.

[barco_75]

What causes 35k volts to jump the tube glass? Can it go through the glass?

[Tim in Phoenix]

Hello

At that voltage, even glass will conduct some.


.

[barco_75]

Ok, so im slightly intimidated now. Not entirely about the voltage but with screwing up the projector. I called my uncle who is a tech who installed CRT and repairs electronics. He admitted it been a long time since he worked on CRT but generally was knowledgable about the layout. However, when I asked about the focus yoke he wasn't aware of one being on the crt tube. Based on this, I think he only worked on older ES focus units and not EM. (see link below for explanation between each type)

http://www.curtpalme.com/CRTPrimer_12.shtm

He advised not to adjust the magnetics because if adjustment is done after the crt's have burn in it can cause bright spots in the image which can't be correct. He also said there should be a pot to adjust the focus in the High Voltage section. I don't see any such adjustment for the Barco 808 graphics. He his comments not applicable for EM machines?

Also, I noticed that my projector does not have the cable from the focus yoke as seen in the attached photo (shown on this website). Should this cable be present? I have the older neckboard machine (non-s). Does this control the electronic focusing accessible from the menus controllable by remote? I notice when I make adjustments in the menu nothing appears to be happening. Perhaps if I install the cable I can sharpen the image without making adjustment to the magnetics.

[Ile]

Your uncles advices are for crt monitors and tv's, not for EM focus projection tubes.

Maybe focus yokes connectors are against mother board. Or does yokes have empty connectors?
Those cables should be installed to get good focus from 808.

Astig magnets control more spot shape than focus. So get focus in control first and then you can test if astig is needed to be adjusted.

Fast astig test:
Adjust electric center point focus 0-100 from menu and same time check if raster (crosshatch) is moving. Static raster usually means that astig is as good it gets.

[barco_75]

Ok, I'll check for the cables. Is the motherboard connection on the board immediately above the rgb amps?

It looks like adjustment on the barco is a little easier than most. I see a black plastic screw adjustment ring on the focus yolk. I guess I just turn that get a fine focus and there is no need to unscrew the clamp for the entire focus yolk assembly and move it unless its grossly out if focus. Is it important that the square bottom of the focus yolk align with the square bottom of the deflection yolk? It looks like the are misaligned by about 15 degrees.

Also on the astig magnets, there are two knobs instead of tabs as described curt and guys instructions. One for two pole and one for four pole, i assume. Should I move both to the start position 180 degrees apart or just make minor adjustments from current location. They already have a line marked across all of them which line up. I'm assuming this was the factory location but I believe the tubes where replaced at some time because the are 7-8 scale and the chassis has 11,000 hours.

[Ile]

[Jeremy112]

Ah the tube magnetics, really quite tedious, but worth it in the end. Just do as everyone says, keep your damn hand in your pocket, or behind your back, so far I've not shocked myself from a projector, a friend did, and by the way he was acting after it, I don't think anyone wants to have it happen to them

[barco_75]

Ile, Thanks for the advice that helps. Jeremy was your friend ok? Was he aching or acting? I'm a little confused by that statement.

[Tim in Phoenix]

Hello

If you find this worrisome, bring in Craig Rounds, his insurance is paid up












.

[barco_75]

Oh, Jeremy now I get your statement. I must have not had my coffee yet! Tim nice photos! What's going on there? Fun science experiment?