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Home Picture Tube Swap DIY - Part 2
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So you wanna swap a tube...   (Part 2)


Last Updated 10/22/2012 - Corrected Typos

WARNING: This article is currently considered "BETA" - meaning, it may be missing a step, there will certainly be typos, and your toaster may get possesed as part of the procedure. Please use this information as your own risk, and if you see something wrong, please let me know by using the CONTACT ME button at the top of the page.


Table of Contents:

<-- In case you missed it - click here to go back to PART 1

Part 2 - Actually Doing The Swap

Work Area
Tools Needed
Prepare The Donor
Let's Begin
Swapping The Yoke
Final Stretch
Flip De Switch!
Final Adjustment and Alignment
More Resources


Disclaimer: As with any articles on junknet.net, please verify any and all facts before putting them to practice. I do not claim to be an expert on these topics, merely sharing what I do know based on my own experiences, forum postings, and from other knowledgeable folks. Use this information at your own risk.

Safety disclaimer: TVs and arcade monitors and anything else with a picture tube contains high voltage, in excess of 15,000 volts! Picture tubes generally require 1000v per inch of tube. As such, use extreme caution when working with this equipment - these voltages are not only dangerous, but could be FATAL if handled improperly. YOU HAVE BEEN WARNED!

IntroductionSmashed Tube

Part 2 - The actual tube swap. Ready? Scared? Don't be - this is actually the fun part hopefully. Keep in mind that tube swaps are a gamble no matter what - its possible the tube may not work, or you can't get it aligned that great, or whatever, but almost 95% of the time, they work great. Let's get started! The patient you see in the pics is a Wells-Gardner K7000 19" monitor. The neck of the tube was smashed to smithereens.

Work Area

Since we're working with some somewhat large items here, its important to have a work space big enough to accommodate at least 2 19" tvs/monitors comfortably. If you don't have a workbench, you can work on the floor but its not fun. I actually did the example swap in my driveway using cardboard boxes as "blocks" per se to protect the tubes. It actually worked very well but if your back's not that great, do what you can to come up with a suitable workspace. It also helps to have padding to lay the tubes on, so you don't scratch them. A folded newspaper works well in a pinch.

Tools Needed

This tools needed will vary based on the make/model of the monitor and donor TV, but generally, you're going to need:

  • Padding (to lay tube on): Folded up newspaper, piece of foam rubber, bubble wrap, mouse pad, or possibly a small box about 12"
  • Standard-Size Philips Screwdriver
  • Long flat-bladed screwdriver (longer the better) with a plastic handle, and a clip lead or piece of wire (For discharging)
  • Nut Driver Set and small socket set for removing boards/tubes (1/4" nut driver and 10mm socket recommended)
  • Good Wire Cutters for electronics (Xcelite makes great electronics tools and available at Radio Shack/Home Depot/Sears/wherever
  • Good wire strippers (radio shack)
  • A small, strong cardboard box or pillow (optional)
  • A friend (an extra pair of hands may help) and a non-alcoholic drink (Any other time fine, but alcohol+high voltage=bad)


Prepare The Donor!

If you haven't done so already, start by removing the back of the donor TV/monitor to get access to the guts. Before you go any further, make sure you discharge it first. Take your long-bladed screwdriver, and attach one end of a clip lead (or wire) to the metal screwdriver shaft. Attach the other end to the bare wire or spring wrapped around the back of the tube. Holding the screwdriver with your right hand and MAKING SURE not to touch any of the metal shaft, and your left hand behind your back, slip the screwdriver under the suction cup on the top of the tube. You will probably hear or see a spark/snap as it discharges, or you may get nothing. Keep touching under the suction cup until the snapping goes away. Once its discharged, you can continue to take apart the donor. When you're ready to remove the tube, prepare your padding on the work surface, turn the TV tube-face-down onto the padding, and remove the 4 bolts/nuts/screws that hold it to the tv frame. The frame will usually fall down from the tube. Lift the tube and get your friend to discard the frame, then put the tube back down on the padding.

Whats the deal with the right hand/left hand thing? Your heart is in the center of your chest, between your shoulders. The last thing you want is if you get a shock, for the shock to travel from one arm to the other, THROUGH your heart. While discharging a monitor is pretty safe, keeping your left hand out of the way ensures that even if you do get a shock, it keeps the path away from your heart.


Let's Begin!

Next we're going to start working on the patient monitor. This assumes the monitor is already removed from the game cabinet. If the tube isn't broken, start by discharging the monitor; same procedure as above. Take your long-bladed screwdriver, and attach one end of a clip lead (or wire) to the metal screwdriver shaft. Attach the other end to the bare wire/spring wrapped around the back of the tube. Holding the screwdriver with the handle your right hand (AGAIN, DO NOT TOUCH THE METAL SHAFT), and your left hand behind your back, slip the screwdriver under the suction cup on the top of the tube. You will probably hear or see a spark/snap as it discharges, or you may get nothing. Keep touching under the suction cup until the snapping goes away.

Once its discharged, start by carefully removing the anode wire (suction cup) by sliding it sideways to unhook it from the tube. Once you remove that, see if there's a black ground wire going from the tube ground-strap (bare wire) to the neck board or the monitor chassis. The wire is usually either attached to the neck board with a small connector that just slides off, or its soldered to the neck board. Its up to you whether to unsolder, but I usually cut the wire about a third of the way from the neck board. If its screwed to the chassis, simply detach it and start the screw back into the hole so you keep it safe for later.

Next, find the group of wires going from the yoke to the chassis. In most cases, they end at a plug that simply pulls off of the chassis. If the plug is glued on, you may have to cut or pull the glue away first. In some cases, 25in tubes have the yoke plugs on the yoke itself. Either way, detach the yoke plug from the chassis, or if 25in, detach the yoke plug(s) from the yoke itself.

Next, find the wires going from the black degausser that surrounds the back of the tube. Its usually a pair that go into a small plug. Again, just pull the plug off the chassis.

Next, carefully slide the neck board off of the tube neck. Again, it may be glued, and if so carefully cut the glue using your wire cutters or a razor blade. Working the neckboard gently side-by-side helps to remove it safely.

Once the tube is completely disconnected, we can remove the chassis. In the case of Wells-Gardner monitors, the chassis is often held on by 2 screws near the back. Remove the 2 screws, and remove the chassis from the frame. Put the screws in your container to keep them safe for later.

The next step is the actual tube removal. Again, like the TV, removing the 4 bolts is often all it takes. How you do it is up to you, however keep in mind that once you remove most of the bolts, the tube may get clumsy and hard to hold up. If you don't have a friend that can help, I actually recommend using a cardboard box or maybe a small (throwaway/disposable) pillow. The box or pillow must be strong enough to hold up the tube and frame while you remove the bolts. Another idea is that if you're working on a workbench, lay the tube face down (on padding) and position it so you can spin tube with one corner sticking off the bench, that way you can remove the bolts one by one and spin it to access the next one.

Suspended TubeIn my example, I'm using the box method since I'm working in a driveway. I cracked each of the 4 bolt loose, then I laid the monitor face-down onto the opening of the box, so it sort of resembles a car up on blocks. I then completely removed all 4 bolts, and was able to simply lift the frame off the tube.

Next, we need to remove the degausser, which is the black wire-looking thing wrapped around the back of the tube. In my case, it was held on by 2 twisted wires on one side, and 2 zip ties on the other side. I cut off the zip ties (I'll need new ones later), and undid the twisted wires. I carefully lifted the degausser off the tube and laid it on the ground, making sure to keep it in the same position it came off.









Next we need to Tube Ground  Strapremove the bare-wire ground strap (called the DAG wire) on the back of the tube. This one is usually easy - its spring loaded. Simply unhook each loop off the tube, making sure you note how it goes back on, and what side of the tube the lead is coming from. A camera and some pics helps, and often I recommend immediately installing it onto the new tube before you forget how. (Speaking from experience here).

Once the ground strap is removed, move the old tube aside (keep it on padding if its not broken!), and place the new tube on your box or padding. Install the ground strap the same way, making sure the lead is on the proper side of the tube.

Next, re-install the degausser the same way it was mounted on the original tube. Exact placement is not 100% necessary, but get it as close as you can to how it was. Again make sure the plug wire is on the same side and position as it originally was, so it reaches the plug on the chassis.





Stand it up

Now you're ready to mount the new tube to the frame. Carefully lower the frame onto the tube, making sure the tube is in the proper position with the suction cup area where it originally was. Start all 4 bolts by hand and turn them in as much as possible. Make sure the frame is evenly positioned on the tube tabs, then use your wrench to tighten the bolts. They don't have to be uber-tight, just "tight" will do. We're not building a car here.

Turn the frame upright, and if all goes well, it should start looking like a monitor again! Make sure again that that the tube is positioned properly in the frame, and make sure the bolts are tight.





Swapping The Yoke


Yoke Swap - Coming Soon


Final Stretch

Once yoke is swapped (if you had to), you're ready to re-mount the chassis. Slide the chassis partway into the frame, enough so that all the various wires (degausser, yoke, etc) reach. Plug in the yoke and the degausser wires, make sure your big red anode wire is out of the way and slide the chassis into the frame. Bolt it back in using the screws you took out earlier. Next, re-attach the anode suction cup by carefully hooking the little wire clip into the hole on the top of the tube. Make sure it is fully clipped on and not loose!! (Sometimes it helps to fold-back the suction cup to get it hooked on right.)

Next, carefully slide the neck board onto the neck of the tube, noting the position of the socket. It does fit, right??

Lastly, re-attach your ground strap wire. If you cut the wire earlier, you'll need to couple them back together with quick disconnects, a butt-splice, or just strip, twist, and use a very small wire nut. (I often use a connector or wire nut in case I ever need to disconnect it again.) If it already had a plug on it, plug it back in.

At this point, your swap should be complete. Before you power anything up, BE SURE to go back and check the following, I've often missed one of these things, so PLEASE, GO BACK AND CHECK THEM, maybe even twice:

  • Ground strap from tube is connected to neck board or chassis as it originally was
  • Big red anode wire is connected to tube, suction cup is hooked on properly and not loose. Wire not leaning against frame anywhere where it can rub.
  • Yoke plug is connected properly to the chassis (make sure you're not one-pin off, use a flashlight if you have to)
  • Degausser plug is connected properly to chassis (again confirm its on right)
  • Chassis is properly mounted in frame. Theres no loose screws stuck underneath and the board isn't touching the frame underneath.
  • Tube bolts are tight, everything overall looks like it should.

Flip De Switch!

OKAY!! Great, we're in the final stretch. Now the all-important test drive. It really helps to have a way to power up the monitor and provide a picture outside of an actual game, but alas not everybody is a monitor tech, so do what you have to do to get the monitor ready to be fired up.

Tip: For monitor testing outside of an actual game, you need a way to power the monitor, and a way to provide a picture. For powering, a generic ISO transformer from any parted video game should work in most cases. If this monitor is a Sanyo from a Nintendo cabinet, keep in mine you CAN NOT plug it in to a wall socket. It specifically needs a NINTENDO isolation transformer that only puts out 100v. Also, most Wells and Electrohome monitors REQUIRE an isolation transformer, again, almost none can be plugged into a wall directly. I use a bench isolation transformer that I'm sure you can find on Ebay, unfortunately these suckers can be heavy so find one as cheaply as possible and check the shipping cost first.

For providing a picture, I use an MT830a test pattern generator. It runs a little over $100 and has been invaluable in testing/repairing monitors. You can find one here or at other places: http://www.tequipment.net/GMETechnologyMT830A.asp

You can also build a cheap little test rig using an Atari "Tetris" board and a jamma harness. The board provides nice test patterns and is very small at about 6in square.

Ok so you have the monitor all hooked up and ready to go. Scared? Nervous? Its normal and you should be - after all the monitors I've fixed, I still get nervous when I fire one up for the first time. Anyhow, before you fire it up, turn the SCREEN adjustment on the flyback down a little. This way you can adjust it properly instead of possibly overdriving the new tube.

If you can help it at all, use an outlet strip with a switch on the game, so you can stay a few steps back. If not, do what you can to keep your body as far from the monitor as possible. You don't want to get the business end of a high voltage arc or a flame. Ready? FIRE IT UP! Pay attention! If you see any blue sparks, flames, or smoke, release the switch or power down IMMEDIATELY. If you simply hear the familiar "woosh" of the static building up - CONGRATS, it survived surgery!

Working Monitor

Final Adjustment & Alignment

Now for the possibly not-so-fun part: Alignment. If you didn't have to swap the yoke, chances are you won't have to deal with aligning the 3 colors together. Simply adjust the flyback's screen and focus adjustments until you see a decent picture, then use the rest of your adjustments to dial in the picture on the screen. If everything looks good, again, CONGRATS! If not, check the following "Troubleshooting" guide for some possible issues and their fixes.







Oh no! Something went wrong or you wouldn't be reading this. CRAP. Ok, take it easy, many things may be easy fixes. Before you proceed, double-check everything from the bullet list at the end of the procedure. Make sure everything is where it should be and all wires are connected properly. Make sure your fuse is good. If the tube was previously broken and the monitor was powered on with the broken tube, its possible the chassis was damaged. Check the voltage regulator and HOT (horizontal output transistor) to see if they're shorted.

REMEMBER: Never touch anything on a chassis while its powered up! There's 1000 volts for every inch of picture tube, but you knew that from the safety warning, right??


Problem: There's no power! (No static, no picture)

Solution: Make sure your game is turned on or the power to the monitor is turned on. Make sure the fuse didn't blow, both on the chassis and the fuse that powers the monitor in the game. If the fuse did blow,  you'll have to troubleshoot the chassis, or its possible the tube isn't compatible.

If you have a multi-meter, set it to AC voltage (squiggly line) and carefully test the power plug for voltage.


Problem: There's power (and static), but no picture!

Solution: Make sure your brightness and contrast settings are turned up. If so, try turning up the SCREEN adjustment on the flyback. If you still aren't getting a picture, or even a raster/haze, make sure the tube neck is glowing. If not, you'll need to troubleshoot the chassis.


Problem: Picture is upside down!!

Solution: Reverse the yellow/green wires on the yoke plug (or the pair thats not red/blue). If you can, simply power down the monitor, unplug that half and spin it around. The wires may be different colors, but you want the pair thats NOT blue and red.


Poblem: Picture is backwards (Mirror Image)

Solution: Reverse the red/blue wires on the yoke plug. If you can, power down the monitor, simply unplug that half and spin it around.


Problem: There's only a horizontal line (That goes from one side to the other)

Solution: Check your yoke wiring, specifically the pair of wires that are NOT red and blue. One wire may be disconnected, or the plug isn't seated properly on the chassis.


Problem: There's only a vertical line (going from top to bottom)

Solution: Check your yoke wiring, specifically the red and blue wires. One wire may be disconnected, or the plug isn't seated properly on the chassis.


Problem: A spark popped, smoke ensued, and the fuse blew!! HELP!

Solution: Didn't read that part about the isolation transformer being REQUIRED, did ya? Chances are you'll have to replace the diodes in the power supply section of the chassis at least, as well as the fuse. Any other parts that popped/burned will have to be replaced too. Again, MOST if not ALL arcade monitors require an isolation transformer.

If you did use an iso, and got sparks or smoke, its possible the tube you use wasn't compatible, or you used a yoke that that was out of range for the chassis, or you missed something as far as a wire being out of place, a screw laying on the chassis, or perhaps the chassis was already bad/damaged anyway. Unfortunately, chassis repair isn't cut and dry and is outside the scope of this article.


More Resources:

Ultimarc Arcade Monitor FAQ

KLOV (Killer List of Video Games) Forums

Bob Roberts (Parts and arcade GURU)


ENJOY! I hope this helped you get your classic game (or perhaps that franken-game built out of spare parts) back up and running again. If so, kind words are always appreciated! Simply use the "Contact Me" button at the top of the page to shoot me an email. Again if you see a typo or some incorrect information, please let me know!


Thanks/Credits: Many thanks to the KLOV forums for providing the know-how to write this article (and do several succesful tube swaps myself).

Copyright 2012 Jeffrey Golas - Junknet.net