Tempest pincushion

Jerware

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Hi, all.

I just bought my first arcade game, Tempest, and it works relatively well except for this nasty pincushion effect. I know that pincushion correction is handled by a pair of MC1495 chips on the main board, but before replacing them or looking for broken traces I wanted to ask the group if this amount of distortion is normal or not. I've adjusted all the pots on the boards, and nothing did anything to fix it. Shrinking the X/Y size had the effect of lessening the distortion, but it's really just a workaround. I'd like to solve it for real.

Also, there are some missing "dots" around the center of the display. Is this typical of an old monitor, or something that can be fixed?

Thanks!
Jeremy
 

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Did you ever solve this?

I have a Tempest that pincushions like this, but it is definitely not the Tempest board, it is my WG6101. I get the pincushioning with any game, and also with my ZVG (with pincushion correction enabled).

It's very strange. I'd like to know if your problem was with your Tempest board or something on your monitor.
 
Did you ever solve this?

Yes, I bought a new main board to fix the fact that the game wasn't saving the top three scores, and that also fixed the pincushion. I didn't expect it to, but it did.
 
Aside from a board problem pincushion correction chip that I've already mentioned. It could possibly be due to your HV is to high, or to low. Or in a rare case something is wrong with your yoke, or the yoke and tube don't match.

I would lean more towards your HV being off. If it affects more than one game.
 
Did you ever solve this?

I have a Tempest that pincushions like this, but it is definitely not the Tempest board, it is my WG6101. I get the pincushioning with any game, and also with my ZVG (with pincushion correction enabled).

It's very strange. I'd like to know if your problem was with your Tempest board or something on your monitor.

Is it possible you have an amplifone/rauland 19" yoke on the monitor?

The correct yoke has a square component to it, Amplifone/rauland is round only
 
The monitor in question is an all-original WG6101. It looks brand new, with no burn, and everything is factory. There was still factory glue on everything, including the flyback controls. It definitely does not have a mismatched yoke. Until I did a cap kit on it, I don't think it was touched by anyone.

I really don't know what is going on. I think I'm going to have to part swap with a different monitor to isolate where the problem is occurring.
 
I know this is an old thread, but just wanted to, yet again, reaffirm the diagnosis that Talon gave as I had the same pincushion problem and replacing MC1495 at A/B12 fixed it right up.
 
For those that solved their problem by replacing the MC1495 chips...



Did you see pincushion regardless of where you "centered" the screen? Or did it only occur at some positions on the screen?



I've got a pincushion behavior, but it only occurs when vectors are drawn near the end of the screen.







I've got another thread on KLOV regarding this, but your input would help. If you saw it all the time, then my problem may not be the MC1495 chips.

UPDATE: looks like it was q706 on the monitor.



... Altan
 
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Glad I found this thread. I am having the exact same issues. Where can I purchase a replacement MC1495? Thanks
 
I spent last night aligning the rebuilt 6100 monitor in my Tempest. Color and alignment is looking pretty good but I do have some odd effects.

On the screen with the diagonal lines you can adjust those lines up or down within the outer box but my lines are not even. So if the diagonal touches at the top on the right they are too low and don't quite reach the top line on the left side. Also the diagonals on the left dip below the bottom line.

On the crosshatch screen I get a pincushion effect. It's not severe but noticeable.

Is this a BIP issue, a chip issue? Any advice about how to fix would be greatly appreciated.

Last question: When I run the test I see an M appear for less than a second and then vanish. I've read 'M' indicates a math box error (2nd board) if it stays on. Does the fact that mine flickers on briefly signal an imminent problem or is this pretty normal?
 

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