Weird monitor problem - never seen anything like this

[Vectorman]

My buddy Jeff does service work in the area but isn't able to figure out how to log in to his KLOV account or post threads, so I'm doing it for him.

Here is a picture he took of a monitor he is trying to repair (vision pro) for a customer. He tried cap kitting it (mostly - he replaced all but 5 or 10 caps).

The only thing that came to my mind was possibly the yoke is not attached firmly to the tube, or some piece of metal slipped down inside the yoke? He didn't check those things yet. Have any of you seen this? Any ideas?

Thanks for any help you can offer!!!

 

[TheYeti]

Definitley looks yoke related. I would be ohming that yoke and checking continuity.

 

[M K L]

Open coil in the yoke. See my post for details:
https://forums.arcade-museum.com/threads/solved-19k7300-troubleshooting-question.539694

 

[Mattspad]

Bad yoke. Could be wrong but try that chassis on a different tube if you can. I know it's a happ Vision Pro which is supposed to be a new monitor but it still can fail. You could probably tube swap it pretty easy worst comes to worst.

 

[ArcadeTechGW]

Or look for broken leads from the yoke.

 

[Sid]

I don't want to derail the thread but does your friend work on video poker machines?
I have a few nice monitors that came from poker machines but do not have the remote boards.
If not I'll post my own "wanted" thread.

 

[Indygameguy]

My buddy Jeff does service work in the area but isn't able to figure out how to log in to his KLOV account or post threads, so I'm doing it for him.

Here is a picture he took of a monitor he is trying to repair (vision pro) for a customer. He tried cap kitting it (mostly - he replaced all but 5 or 10 caps).

The only thing that came to my mind was possibly the yoke is not attached firmly to the tube, or some piece of metal slipped down inside the yoke? He didn't check those things yet. Have any of you seen this? Any ideas?

Thanks for any help you can offer!!!

This is Jeff - it's been a long time since last login but finally remembered my password. I know I could've just changed it but considered it a memory challenge.

I don't work on pokers normally, but this guy called on a Ms. Pac and asked if I could look at this while there. Sid - Unfortunately I only have a few extra remote boards for various monitors and need to hang on to them.

Thanks for all the tips guys. I went back and checked the yoke. It was securely in place where it should be with no broken wires or apparent signs of damage or any foreign object in it. On the yoke connector one axes measured about 6 ohms and the other axes about 24. All pins are making a good connection to the chassis and I also pulled the chassis to test the traces coming off the yoke pins. Everything looks good.

I couldn't find what the proper resistance values should be for this particular yoke (MTG-2901CN chassis with an LP Displays tube), but I'm just going to assume the yoke is bad and keep my eye out for another compatible yoke or tube.

 

[Mattspad]

This is Jeff - it's been a long time since last login but finally remembered my password. I know I could've just changed it but considered it a memory challenge.

I don't work on pokers normally, but this guy called on a Ms. Pac and asked if I could look at this while there. Sid - Unfortunately I only have a few extra remote boards for various monitors and need to hang on to them.

Thanks for all the tips guys. I went back and checked the yoke. It was securely in place where it should be with no broken wires or apparent signs of damage or any foreign object in it. On the yoke connector one axes measured about 6 ohms and the other axes about 24. All pins are making a good connection to the chassis and I also pulled the chassis to test the traces coming off the yoke pins. Everything looks good.

I couldn't find what the proper resistance values should be for this particular yoke (MTG-2901CN chassis with an LP Displays tube), but I'm just going to assume the yoke is bad and keep my eye out for another compatible yoke or tube.

Can you post some pictures of the tube and the neck of the tube. If we can see the number of pins we can help you find a compatible tube/yoke to swap in there. Also welcome back!

 

[Indygameguy]

Can you post some pictures of the tube and the neck of the tube. If we can see the number of pins we can help you find a compatible tube/yoke to swap in there. Also welcome back!

I did happen to take just this one from the first visit, but realize it won't be much help. Your question about number of pins reminded me that not all 19" Vision Pro tubes are compatible. I tried to swap a chassis several years ago and was surprised to find this out. I'm pretty sure this is the version with the smaller size neck and pinout.

BTW, I was going to look for a solution in my stock but it will take some time. My parts are really spread out in different locations. I appreciate the offer to help and will post again if I need assistance.

 

[mecha]

I did happen to take just this one from the first visit, but realize it won't be much help. Your question about number of pins reminded me that not all 19" Vision Pro tubes are compatible. I tried to swap a chassis several years ago and was surprised to find this out. I'm pretty sure this is the version with the smaller size neck and pinout.

BTW, I was going to look for a solution in my stock but it will take some time. My parts are really spread out in different locations. I appreciate the offer to help and will post again if I need assistance.

yeah I believe I've seen them in skinny (8-pin) and fat neck (10-pin)

don't the neckboards take either socket though? I can't visualize it right now, but APAR sells various sockets.

 

[M K L]

The 24 ohm reading on the vertical proves that one of the coils is open as a normal reading would be 12 ohm. I see you're more inclined to replace the yoke than to fix it so I'll stop here.

 

[Mattspad]

The 24 ohm reading on the vertical proves that one of the coils is open as a normal reading would be 12 ohm. I see you're more inclined to replace the yoke than to fix it so I'll stop here.

How does one fix a yoke with an open winding? I'd be interested to hear!

 

[M K L]

How does one fix a yoke with an open winding? I'd be interested to hear!

The vertical coil consists of two coils (AB and CD) wound around two semitoroidal cores:



The coils can have a series arrangement when B is connected to C. In this case, if either coil goes open it will result in a completely collapsed picture (thin horizontal line). If the coils are in parallel (A connected to C, B connected to D) and one goes open, you'll have the kind of collapse seen in the first post.

To fix it, the first step is to unsolder the coils as in the pic above and measure the resistance across the loose wires. The pair that reads open is the bad one.
Assuming the broken point is not visible, the second step is to remove the semitoroidal core with the bad coil from the yoke. This way you won't have to reconverge the yoke later.
The third step is to give the part a good wash and then inspect it carefully until you find the broken point. Once you find it, you solder the wires together somehow and put the core back on the yoke etc. That's it.

Here's a practical example (but in this case the broken point could be found easily without going through the above steps):

https://forum.arcadeotaku.com/viewtopic.php?t=38750

 

[Mattspad]

The vertical coil consists of two coils (AB and CD) wound around two semitoroidal cores:

View attachment 852303

The coils can have a series arrangement when B is connected to C. In this case, if either coil goes open it will result in a completely collapsed picture (thin horizontal line). If the coils are in parallel (A connected to C, B connected to D) and one goes open, you'll have the kind of collapse seen in the first post.

To fix it, the first step is to unsolder the coils as in the pic above and measure the resistance across the loose wires. The pair that reads open is the bad one.
Assuming the broken point is not visible, the second step is to remove the semitoroidal core with the bad coil from the yoke. This way you won't have to reconverge the yoke later.
The third step is to give the part a good wash and then inspect it carefully until you find the broken point. Once you find it, you solder the wires together somehow and put the core back on the yoke etc. That's it.

Here's a practical example (but in this case the broken point could be found easily without going through the above steps):

https://forum.arcadeotaku.com/viewtopic.php?t=38750

Thank you for sharing, read this over a few times. Makes sense, I guess it just depends if you can successfully do it. If you can find the break and actually make the solder stick it's repairable. Never seen someone separate the core of the yoke like that but it's genius, yeah don't need to mess with convergence. I guess what's he got to loose by attempting to fix it, could be worth a shot.