Help with bad corner convergence

[jrickle]

Hello world,

I've got a TEKKEN 5 DR cabinet i've had for a while, and am finally getting into and learning more about the internals. I'm slowly working on dialing it in better and better, but I cannot for the life of me get this convergence to an acceptable amount. I tried convergence strips (i may not have used enough, after learning more i realized how many a monitor this size might need.) but i can't get it to get even close to where it should be. The center looks focused, but the outer edge (especially the bottom left) is almost unreadable. I also tried fiddling with the convergence rings at least a little, but it didn't seem to affect it much. Do I just need more patience? or is there something else I should look at? I've attached some (best i can) pics for reference. Help much appreciated!

 

[nem]

You can't fix that with convergence strips alone. There's something else at play here, my guess is missing magnets on the rim of the yoke. What monitor is this? Can you take a picture of the yoke?

 

[jrickle]

Thank you for confirming my suspicions. Glad to hear it's not just my patience that's the problem It's a Sanwa 29PF31, with a 29E13S chassis, standard on Tekken 5 cabinets as far as i've seen. I was thinking it was something to do with the yoke, but am not experienced enough to make that call with certainty. I've left it mostly untouched from when I picked it up, besides the few strips I threw in to see what I could do for convergence. My last ditch effort would've been simply pushing the yoke forward, since it looks like the picture is just out of focus (focus pot is maxed out and gives me the image quality in the first pics.)

 

[nem]

Looks like the magnets are all there. Does the yoke move if you touch it? It should be pressed firmly against the rubber wedges.

 

[jrickle]

No movement with touching it. I loosened the yoke clamp and tried to give it a gentle push forward, but no dice. I did however notice that it looks like something vaguely magnet-looking is missing from the right side of the tube. (peeled the sticker off of the left one to show what was there originally. Not sure if its a magnet or some other piece i'm unaware of.) The top wedge looks to have a little space between it and the yoke, but I think glue is keeping it from moving at all.

 

[Big_P Big_p]

Yeah that looks like an adjustment magnet which are used for corner convergence issues. Basically a low powered (fridge?) magnet and double sided tape will work. Align on the diagonal between the yoke and corner with the issue. The closer to the yoke and the more powerful the magnet the greater the effect. It takes ages moving, spinning and flipping the magnet to get it in the right spot. Voltages are high back there so remove your watch and any jewellery, stay away from the anode cap and red wire and you can wear electrical gloves. Convergence strips may work but bigger issues typically require a magnet. 29" tubes are big and almost impossible get get 100% perfect so sometimes it's a compromise between this issue and that issue. There are a few good videos on thus type of issue. I have a similar but worse issue I am going to have to tackle soon on the Chandy Cab.

 

[trashedcabs]

If you absolutely cannot get the corners to focus with the focus pot you need to rejuv it. Guaranteed if you check the tube health it will show low emissions. These novel tubes are crap and all do this, likely caused by premature cathode wear.

 

[nem]

I've never had any lasting results rejuvenating these tubes.

 

[jrickle]

thank you all for your help! I've got some magnets coming in today, and i'm gonna see how that affects my convergence. Rejuvenating is something that I would like to do in the future, as it has subpar brightness and I think that a good jolt would be good for it. From the little I can find, it does seem like these tubes tend to lose their color and brightness pretty often though. I still haven't recapped yet, and that's another plan in future, which hopefully will help as well. I'm a soldering newbie though, so I want to practice on something less expensive and difficult to replace

 

[Big_P Big_p]

Tube rejuvenation is an absolute last resort. Try magnets, adjust brightness on the chassis via the chassis brightness pot and bottom flyback pot, recap, check B+ voltage and if all that doesn't work then and only then consider a tube rejuvenation. My experience with Tube rejuvenation is that it considerably shortens the life of the Tube and that in longer term the results are marginal at best, with most issues able to be solved with other interventions.

 

[trashedcabs]

Tube rejuvenation is an absolute last resort. Try magnets, adjust brightness on the chassis via the chassis brightness pot and bottom flyback pot, recap, check B+ voltage and if all that doesn't work then and only then consider a tube rejuvenation. My experience with Tube rejuvenation is that it considerably shortens the life of the Tube and that in longer term the results are marginal at best, with most issues able to be solved with other interventions.

None of these will solve the excessively poor edge focus. My understanding is that the middle of the cathode surface becomes either worn or poisoned, causing the edge of the surface to emit. This reduces emissions and also focus as the electrons essentially need to travel further/at an angle from the grids. A rejuv burns off the bad material on the center of the plate, improving the emissions and focus.

Most rejuvenators have a "restore" option which effectively "boils off" the bad material using low-current at a longer duration, and is generally fairly safe. According to my CR-70's manual, the higher current "rejuv" function should not damage anything as long as it's only used once. Personally, this has been my experience--once a tube requires more than one rejuv it's usually on its last legs, but if it responds well then it may have many years of life left, especially in a home environment where it won't be on 24/7.

I've never had any lasting results rejuvenating these tubes.

Yeah, the novel tubes are pretty trash. I've personally had 3 develop shorts which were not fixable, but one that showed low emissions and after a simple restore is still running today.