Jump to content
Due to a large amount of spamers, accounts will now have to be approved by the Admins so please be patient. ×
  • 0
IGNORED

Monitor Geometry (Trapazoid/Keystone) issue/adjustment


powerofthejam

Question

Hi guys,

 

Wondering if anyone is able to steer me in the right direction on this one. Just looking for a bit of advise on what I should try next or what I should be looking for as I'm mostly a novice when it comes to CRT's.

 

Bit of background, I have a lowboy cab that I acquired sometime back around 2007. I used it briefly and the monitor had no issues. Fantastic picture. I transported it interstate (VIC to NSW) and stored it for a decade. I've now transported it back to VIC and hooked a CPS2 up to it but the monitor now displays some very obvious geometry issues. Troubleshooting monitors is not something I've done before, outside of tweaking the pots on the chassis. The image now appears a lot thinner at the bottom and the colours not only are not converging, but they appear to be at completely seperate angles, like so.

geometry.png

 

The chassis is a Nanao KB24033ID.

I've tried changing game boards, degaussing, adjusting the chassis pots, flyback pots and adjusting the convergence rings, all to no effect. There's no keystone knob i can see that I could adjust. I assume something has been knocked in transport or degraded over time but I'm unsure what to attempt next.

 

I've attached some pictures. If someone can steer me in the right direction that would be much appreciated. If any additional pictures will help diagnose, please let me know.

 

Cheers

 

1.jpg

2.jpg

3.jpg

4.jpg

5.jpg

6.jpg

7.jpg

8.jpg

9.jpg

Link to comment
Share on other sites

14 answers to this question

Recommended Posts

  • 0

Wow, your tube convergence is really, really out of whack there. You need to do a yoke adjustment and that is far beyond the skills of an ordinary person. The yoke has definitely been badly moved and needs to be fixed.

 

To do that, you need to have the monitor running, while you adjust the angle and orientation of the yoke. It is not for the faint of heart and can be quite dangerous. The people who did this when the CRTS rolled off the production line had some proper training.

 

To be honest, unless you can find a really hardcore CRT tech to do this for you, or get a new tube to match the chassis, the monitor may be not worth saving. No amount of pot adjustment will fix these issues, it will have to be yoke and convergence ring adjustment.

Link to comment
Share on other sites

  • 0

First thing I'd be looking at is under the yoke, there's a good chance you may have some corrosion there caused by the brown glue or the rubber wedges.

Adjusting the convergence rings won't fix this and need to be put back as they were.

If you leave the monitor running, you will risk damaging the horizontal section which will result in no picture at all.

Removing the yoke is a delicate process, use a marker to make a line across the rings to the neck of the tube so when you reinstall them you won't need to realign them.

When reinstalling the yoke don't worry too much if your picture is not perfectly level, this can be adjusted by turning the yoke clockwise or anticlockwise to get a level picture again.

Oh and don't over tighten the clamp screws, you may break the tube neck.

Link to comment
Share on other sites

  • 0

There's been a few threads like this over the past year. This is caused by one of the horizontal coils of the yoke being open-circuit.

 

@powerofthejam have a look at this pic

 

9b68ec7e5e47b7672d671c423d0e51c1.jpg

 

And this post by soyl, replying to it.

 

That's not a convergence issue, it's a deflection issue caused by a defective yoke. The horizontal yoke is made of two identical coils wired in parallel and if one of them breaks (burned/corroded) you have only one and the resulting picture will look like the one you have. So the first step is to check the horizontal coils and see if one is actually broken. This is done by desoldering the coils where they join together and test continuity across the two pairs.

 

You can use a multimeter on the yoke to test first, i'd say, looking for the resistance value across the red and... whatever other wire gives a reading. report back the withe value, but i'm guessing you'll get around 4-5ohms. Lower than that might indicate it's ok but it reckon it won't be. If one coils is broken, and you can't see the problem where the wires connect, you can look fro a new yoke, or try unwinding and fixing the one you have. There are some success stories on arcadecontrols re this, but no actual tips :)

 

With thanks to @soyl for his help :)

 

- - - Updated - - -

 

And then this video provides a nice guide to setting the tube up again if needed. Remember that it's not always this easy; you can expect it to take 3-4 hours to get right the first time, especially if you're a perfectionist. And you'll probably want some convergence strips too :)

 

Link to comment
Share on other sites

  • 0
Thanks for the input. @buttersoft , that looks identical to my issue. I think in this case I'm better off having a professional technician attempt to repair it.

 

Just remember to mention that it's probably the tube (or yoke) not the chassis. Nothing certain. Easiest and cheapest might be to get a new tube...

 

While remembering that tubes can hold charge, and you'll want to discharge unless you're autosteve, who apparently likes getting zapped :D

Link to comment
Share on other sites

  • 0
Just remember to mention that it's probably the tube (or yoke) not the chassis. Nothing certain. Easiest and cheapest might be to get a new tube...

 

While remembering that tubes can hold charge, and you'll want to discharge unless you're autosteve, who apparently likes getting zapped :D

 

Yep, finding someone to repair it will be difficult enough and if you do find someone, it will likely be expensive. If you were in Perth, you could take the entire monitor to Joey. Aside from Joey, there would be very few people left who will work on an old arcade monitor. A new tube or an entirely new tube + chassis will likely be the best way to get this up and running again.

Link to comment
Share on other sites

  • 0

Hi guys,

 

Quick update. Turns out I know a guy who knows a guy who knows a guy with a wealth of experience repairing CRT's. I'll consider myself lucky on that front. The shadow mask on my monitor had collapsed. I had the tube replaced and it's now displaying a beautiful picture.

 

Many thanks to those of you that provided input. It was quickly apparent I was out of my depth. Good opportunity to learn though.

 

As an interesting side note, I was advised that the tube (Orion) I had in there wasn't a match for the chassis and the tech wasn't sure how it was ever working in the first place. He was able to source a matching one for me.

Link to comment
Share on other sites

  • 0
Hi guys,

 

Quick update. Turns out I know a guy who knows a guy who knows a guy with a wealth of experience repairing CRT's. I'll consider myself lucky on that front. The shadow mask on my monitor had collapsed. I had the tube replaced and it's now displaying a beautiful picture.

 

Many thanks to those of you that provided input. It was quickly apparent I was out of my depth. Good opportunity to learn though.

 

As an interesting side note, I was advised that the tube (Orion) I had in there wasn't a match for the chassis and the tech wasn't sure how it was ever working in the first place. He was able to source a matching one for me.

 

Wow, that's a great outcome. Finding a CRT tech in this day and age is a challenge. Being able to match a tube to your chassis is really lucky. Glad to see a good outcome rather than a dumped CRT.

Link to comment
Share on other sites

  • 0
Hi guys,

 

Quick update. Turns out I know a guy who knows a guy who knows a guy with a wealth of experience repairing CRT's. I'll consider myself lucky on that front. The shadow mask on my monitor had collapsed. I had the tube replaced and it's now displaying a beautiful picture.

 

Many thanks to those of you that provided input. It was quickly apparent I was out of my depth. Good opportunity to learn though.

 

As an interesting side note, I was advised that the tube (Orion) I had in there wasn't a match for the chassis and the tech wasn't sure how it was ever working in the first place. He was able to source a matching one for me.

 

I cant say ive ever seen a shadow mask cause that, but i guess if it was miles out of place it could cause this.

 

If it was the shadow mask it shouldve been stupidly blury, where as a deflection yoke failure would remain reasonably sharp, and affect linearity.

 

Movement of a deflection yoke will have an effect, but never that significant.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...