NEC XG 1350 Tube Replacement

Written by John Robinson, October 2002

Updated, and pictures added, January 2004

Introduction

This procedure will be the same for all non liquid-coupled XG projectors. LC XG projectors will be the same, except the removal of the lenses will be different

Clicking on any of the pictures on this page will take you to a much larger view of the same picture

Preparation

     If you are not comfortable working amongst electronics and potentially lethal voltages, then I would recommend that you don’t do this yourself.

     Make sure that the projector has been turned off for a while. Overnight is good. This gives the high voltages a chance to discharge.

     Remove the power cable

     Make sure that the projector is sitting on a table at a comfortable height; you’ll be bending over looking into it for a long time!

     Only a madman would even consider doing this while the projector is mounted in the ceiling.

     Make sure that you have read this guide and understand it all before you start

     You need a large philips-head screw driver, preferably magnetic, and a large flat-blade screwdriver.

     Allow about 3 hours to replace the tubes, and then another 3 hours to get all of the adjustments done.

     Take a look at the picture below so that you know where everything is.

Remove the Front Cover

     On the top of the projector where the top cover meets the front cover, there are two fold-down tabs. Lift the tabs, and loosen the 4 screws. They are captive, so you won’t be able to remove them completely.

     Remove the front cover

     Remove the foam surrounds from the red and blue lenses

Foam Surrounds around red and blue lenses

Remove the Top Cover

You will have already loosened the screws for the top cover in the last step. Remove the top cover by simply sliding it back and lifting it off

Lift the deflection board carrier

The deflection board carrier is hinged to the cross member. There are two screws at the back of the carrier that need to be loosened. These are captive so you won’t be able to remove them.

Lift the rear of the carrier and it will hinge up over the cross member. Be careful when lifting the carrier, there are two looms of wires, one on each side of the carrier, that go to the projector innards below. You need to make sure that these two looms are as far forward as possible, otherwise you will stress them when lifting the carrier. Also beware that whenever you replace the carrier, these two looms will move back again, so you have to move them forward each time you lift the carrier

Deflection Board Carrier lifted to expose the tubes and electronics

CHECKPOINT!

Check the CPC (astigmatism) magnets at the back of the neck. If these haven’t been adjusted before they will a few lines of white sealer across the six magnets to hold them in place.

If yours have been broken, and your astig adjustment is OK, I suggest putting some silicone or similar sealer across the magnets before proceeding and letting it dry fully. This may (no guarantees) save you from having to do a full astig adjustment later on

Remove the neck-board covers

You will see three black earthing wires, one from each neck board, that mount to the aluminium neck board covers. Loosen the screws (no need to remove them), and unhook the wire from the cover.

There are two separate covers for the neck boards, one is mounted by 4 screws, and the other by 3. Remove all of these screws, and lift out the neck board covers.

Neck board covers in place

Neck board covers removed

Remove the Lenses

     There are 4 screws that hold each lens in place. Do one lens at a time. Remove the bottom screws first.

     The lenses are heavy! Make sure that they are adequately supported as you remove the last screw!

     It’s easiest to remove the green lens first, as it gives you more space to remove the other two

     Be careful!

All lenses removed.

Note the cracked Green tube!

Remove the Tube Mounting Screws

     Lay down the deflection board carrier

     Take note of the position of the focus rings so that you can set them back again later

     In the cross member, above each tube are two Philips head screws and two long rods. Remove all of these rods and screws. These are all that holds the tubes in place!

CRT Mounting screws in cross-member

Lift the Cross Member

     Before you do this, just place some packing underneath the necks of the tubes so that they don’t fall

     Lay down the deflection board carrier

     Look at the front of the cross member. On each side is a short rod, and a Philips head screw in a slotted hole to locate it the cross member.

Cross Member mounting bolts

Remove both of the rods

Loosen the screws, lift the cross member so that the screw is at the very top of the slot, and then tighten the screw so that the cross member is held in its lifted position.

Remove the Blue Tube

I recommend removing the blue tube first, and refitting it last. The reason for this is that the HT leads from each tube are mounted down beside the blue tube, and there isn’t much room to remove and refit these leads while the blue tube is in place.

When you remove these leads (a little later on), take care to only pull on the rubber boot, and not the lead, otherwise it will break. They will be very hard to remove; you just need to be persistent. Removing the side panel (it’s only held in place by 4 screws, but you need to remove the lower front panel and rear panel to get to them) will reveal a large hole in the side of the chassis, right where the HT connector block is, allowing even better access.

HV Block in side of projector

Be careful that there may be some residual charge left here, and it will hurt if you get belted by it. Play it safe and discharge each connector by shorting it to the chassis with a screw-driver.

     Take a fine point permanent marker, and mark the positions (both fore-aft and rotation) of the CPC magnets and the focusing magnet on the neck of the tube, this will help when reassembling on the new tubes.

     Loosen the screw that clamps the neck board to the neck. Note that the neck board is not mounted by any other means other than its connection to the tube.

     Loosen the screw that clamps the CPC magnets to the neck, so that you can rotate and move the whole set of magnets as one unit. Be careful not rotate any of the magnets separately or you will break the line of white sealer and have to readjust the astig later on.

     Loosen the thumb screw that clamps the focusing magnet to the neck so that it is free to move

     Loosen the thumb screw that clamps the yoke to the neck to that it is free to move

     Beware that there is a split sleeve that goes in-between the focusing magnet and the yoke. You can remove it now or later, just don’t lose it!

     NOTE: The blue and red tubes have a pivot point on the outside, where the outside rod that you removed earlier attaches to the base. This is what allows them to rotate to align them with the green tube. You need to lift the tube by about 4mm over the pivot before it will move forward

     Move the tube forward by a few centimetres.

     Remove the neck board from the neck by pulling back on it. Be careful not to bend the board or stress the neck while doing so.

     Take the little piece that is protecting the neck connector on the new tube, and place it on the old tube. The pins on the tube bend very easily, and this little protector will prevent that from happening.

     Move the tubes forward a few centimetres at a time, and then slide back the magnetics off the tube after each movement. When you have clearance, remove the blue tubes HT lead from the connector beside the blue tube. Take your time doing all of this, just move a few centimetres at a time.

     Remove the blue tube.

     Remove the cast iron tube mount from the tube by removing the 4 screws on the back of the mount.

     Transfer the markings you made on the neck to the new tube.

     Transfer the connector protector to the new tube.

     Attach the new tube to the cast iron mount.

     Leave the blue tube aside for now.

     Remove the HT leads for the red and green tubes from the connector near the blue tube.

Remove the Green Tube

Removal of the green tube is identical to the blue tube except that there is no pivot point on the green tube

Refit the Green Tube

     Refitting the tube is the opposite of removal. Take it slowly, a few centimetres at a time, sliding on the magnetics as you go. Don’t forget to refit the split sleeve that goes between the focusing magnet and the yoke!

     Just before the tube is fully home, remove the little plastic protector from the connector, and carefully slide on the neck board. You will need to be firm with it, but try not to stress the board or the neck.

     You will probably need to lift the back of the neck to get the tube to go in fully.

     Push the yoke up against the back of the tube, rotate it so it is roughly in the same position as it was, and just tighten it up enough to stop it from moving.

     Fit the split sleeve and move it up against the yoke.

     Push the focusing magnet up against the yoke, rotate it so it is roughly in the same position as it was, and just tighten it up enough to stop it from moving.

     Position the CPC magnets where they were on the old tube, and just tighten lightly.

     Tighten up the screw that clamps the neck board to the neck.

     Fit the HT lead to the connector over near the blue tube. Make sure you press it all the way home.

Remove the Red Tube

Removal of the red tube is identical to the blue tube except that the pivot point is on the opposite side.

Refit the Red Tube

Refitting the red tube is the same as the green tube, except you have to lift the tube over the pivot and mount it on the pivot to get it all the way home.

Refit the Blue Tube

Refitting the blue tube is the same as the green tube, except you have to lift the tube over the pivot and mount it on the pivot to get it all the way home.

Connect the HT lead before you get the tube fully home.

Refit the cross member

     Loosen the two screws that were holding the cross member in its lifted position

     You will need to lift the back of the tubes to get the cross member to come down.

     It helps if you replace the Philips head screws that mount the tops of the tubes to the cross member at this point, and just nip them up tight.

     Replace the rods that go though the bottom of the tubes, you will need to lift the back of the tubes and wiggle them around gently a little to get the threaded part of the rod to line up with the hole. No need to tighten them up yet.

     Refit the short rods into the cross member mount and tighten

     Tighten the screws in the slotted holes.

Refit the Lenses

Refitting the lenses is the opposite of removal, except that you should fit the top screws first.

Don’t forget to position the focus rings properly before tightening the lenses up

CHECKPOINT:

Just double check that everything is connected, and that the magnetics are secure. They don’t need to by fully tight yet, as you still need to adjust them

Power up Projector

     Power up the projector

     Turn the brightness and contrast down to around 50 each

     Feed in a signal and let it run for a few minutes to get things starting to warm up. Listen for peculiar noises. I’m told that a few crackles are normal, but mine didn’t do this.

     Spend a few minutes and zero out all of the convergence data you have so that you can start from scratch. Don’t forget about zero-ing out astig (centre, edge, and corner), focus (centre, edge, corner), position, etc etc etc.

     Enter the factory mode (use passcode 3151) and zero out the tube hours.

Adjust rotation

     While the projector is warming up, put some masking tape on the frame around your screen. Put a piece about half way down on each side, and half way across top and bottom. Measure the half way point, and mark it on the masking tape.

     Bring up the cross-hair test pattern

     Doing one tube at a time, loosen the thumbscrew that clamps the yoke, and rotate it so that the horizontal line is in fact horizontal, using the marks on the masking tape as a guide. Don’t worry too much if the height isn’t right, you can fix this later.

     Tighten the thumbscrew up properly. As with all of the clamps on the on tube necks, just tighten them so that they won’t move. Nothing good can come from over-tightening these clamps!

Adjust Phase

Adjust the phase as per the procedure in the manual; this will help centre the green tube.

Adjust Basic Focus

     Adjust the centre and edge focus for each lens using the wing nuts on the top of the lens

     Bring up a cross-hair pattern

     Rotate the focus magnet until the focus is tight. Rotating it one way will tighten the horizontal line, and soften the vertical line, rotating the other way will do the opposite. Find the centre point.

     If you still can’t achieve a tight focus, you’ll need to adjust the focus pots on the wave board. You’ll see them, marked, at the back of the projector on top of the card cage behind the red tube.

Converge and Focus Lenses

     Bring up the cross-hair pattern again.

     For the blue and red tubes, loosen the two screws and two rods that mount the tube, and then move the lens so that the vertical lines line up with the green vertical line.

     Tighten the screws.

     Adjust the centre and edge focus for each lens using the wing nuts on the top of the lens again

Adjust Raster Centreing

     Bring up the cross-hair test pattern

     Zero out the raster-centreing values for each tube.

     Centre the raster of the green tube using the raster-centreing

     The vertical lines of the red and blue tubes should be pretty close from the previous step, so just tighten them up using raster-centreing.

     Mainly adjust the vertical raster centreing of the blue and red tubes using the raster-centreing control.

Adjust astigmatism (CPC) magnets

Bring up the astig test pattern, making sure that all of the settings are zeroed out.

All going well, you will be able to get the astig close to perfect to simply moving the CPC magnets, either fore-aft, or rotation, or both. If you can’t get it close, you’ll need to go through a full astig adjustment as per the manual

Adjust Raster Centering

Now go back and readjust the raster-centreing, but take more care to get it spot on this time around.

Converge and Focus Lenses

Now go back and readjust the mechanical convergence and focusing of the lenses, but take more care to get it spot on this time around

Electronic adjustments

Now you’re ready to start electronic convergence for each source that you have. Have Fun!