Trouble shoot, Thought it was the monitor BUT.....Punch Out

sugar_ray

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Trouble shoot, Thought it was the monitor BUT.....Punch Out

Hello everyone

Just restored my first game Punch Out. Used laminate for the cab, new side art, new overlay etc....

Anyways. My bottom monitor seemed to have been acting up. Weird colors is the best way of describing it. For example, all the opponents in the game have BLUE hair. I ordered and successfully installed a cap kit for the monitor. However NO change. Because Punch Out has 2 identical Sanyo monitors in it I decided to SWAP monitors. Remember the top monitor is perfectly working fine. After swapping I discovered that I was getting the SAME results on BOTH monitors. Meaning the problem lies in the PCB "output"

Should I even bother troubleshooting the PCB? Or is it a lot easier and painless to replace the entire PCB with a known working one?

Not sure if this problem triggers an easy fix for someone reading??

thanks
 

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is the cage filter pcb still there? if so, remove it and plug the harness directly into the pcb.
 
great suggestion! Just tried it. SAME result when bypassing the cage filter.
NOT overly a big deal. Would be nice to have the game function 100% properly
 
it kind of looks like to me that you need to turn the blue drive and/or cutoff down a bit. On the first screen on mine, there's no blue lines around the text.
IIRC, i had a hard time getting mine all dialed in after a cap kit as well.
 
Hi cdjump

The game use to work as it SHOULD (no blue lines during tittle screens) then one day years ago, it started acting up. It has been in storage for a while, I just brought it out and restored the cab. THOUGHT it was the monitor, that's why I capped it to begin with. However, after swapping monitors with a known good working one, I now know its the board

Fairly new at troubleshooting. Could you describe this procedure??

"turn the blue drive and/or cutoff down"

I thank you for all your suggestions
 
Hello everyone


Not sure if this problem triggers an easy fix for someone reading??

If you've swapped monitors and the problem did NOT move with the monitor, it sure is a board problem.

I'd be taking a close look at the color proms, there's a few other things that can cause incorrect colors, but a bad color prom is usually the fault.


D
 
I have located the color proms on the backside of the board. Even pulled them one at a time then tested the monitors with each prom out getting various UGLY results. How would one determine WHAT prom is the problem?

Or just much easier to find a donor board
 
It could be a color prom, but, your reds look purple to me, and the blue background around the text leads me to believe that the monitor needs adjusting- i could be wrong, though.
I'm not trying to be vague - its just been awhile since i fiddled with a 20ez. Normally, the drive and cutoff pots are on the neckboard on the monitor. You can download the manual here - http://arcarc.xmission.com/PDF_Monitors/
Modessitt has a good explanation of adjusting a monitor here -
http://forums.arcade-museum.com/showthread.php?p=352361&highlight=adjusting#post352361

If you capped the monitor, you will almost definitely need to adjust the colors to get it looking right.
 
just out of curiosity, if you don't mind, post a picture of the top monitor - i'd like to see what the colors look like on it. Was it capped as well as the bottom monitor?
 
cdjump

thanks again for all your suggestions! Im fairly sure its NOT the monitor. I have posted some pics that show the SAME results on BOTH different monitors. By swapping wires. Top harness to bottom monitor and bottom harness to top monitor I get SAME thing. Which leads me to believe that its something on the board

BEFORE swapping the bottom monitor had that BLUE around the text. AFTER swapping, the bottom monitor became FINE and it was the top monitor that had the BLUE box around the text. Your "RIGHT" the red is slightly purple.

I have "ONLY" capped the bottom monitor as I thought that was the problem to begin with. I "DO" have a second cap kit for the upper monitor but have NOT capped it yet
 

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what i wanted to see was how the white looked in the top monitor - it looks ok, so i'd assume its not too bad out of whack adjustmentwise. The color proms would be an inexpensive place to start. I've got a PO here, but i've yet to have board problems with it - so i'm not really familiar with how the video works on it, but if it has transistors in the video circuitry, i'd test them out as well.
If you haven't already, i'd clean the legs and reseat the color proms, and socketed rams. You never know, you might get lucky.
 
thanks again! You could just save me a lot of trouble and send me YOUR PCB. :) Jokin!

I shall post if i figure out the problem

cheers
 
My guess is either a color PROM issue, or the addressing circuitry that accesses the PROMs. The fact that the character background color is incorrect while the forground color is fine could clue you in on which part of the video circuitry is messed up.

If you find that you just can't find the source of the issue and you're looking to have the PCB repaired, PM me. I can add you to the queue. ;)
For some reason Punchouts seem to be hot on the list these days. In fact I'm sending out x77x's repaired PO PCB tomorrow.
 
hmmmmmm........ looks like I may be getting somewhere with this.
One thing still puzzles me though. Have a peek at these and tell me what you think.

When I remove color prom 8F (BLUE) Lower monitor and completely leave it OFF the board. Everything is back to as it should. However, it has a slight yellow shading to it (hard to notice in pics) even harder to notice when tinted plexi is on the game.

So my immediate thought was "ok bad Blue lower monitor color prom"

However.....when I move the GOOD Blue from the top monitor to the lower socket there is UGLY results.

Is the Top Blue and bottom blue of a "DIFFERENT" flash for these chips? Kind of thought they were the same bipolar color flash??

I can order a lower Blue replacement chip, just wanted to be reasonable sure that is the troubled prom.
 

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hmmmmmm........ looks like I may be getting somewhere with this.
One thing still puzzles me though. Have a peek at these and tell me what you think.

When I remove color prom 8F (BLUE) Lower monitor and completely leave it OFF the board. Everything is back to as it should. However, it has a slight yellow shading to it (hard to notice in pics) even harder to notice when tinted plexi is on the game.

So my immediate thought was "ok bad Blue lower monitor color prom"

However.....when I move the GOOD Blue from the top monitor to the lower socket there is UGLY results.

Is the Top Blue and bottom blue of a "DIFFERENT" flash for these chips? Kind of thought they were the same bipolar color flash??

I can order a lower Blue replacement chip, just wanted to be reasonable sure that is the troubled prom.

Well, your understanding of what the PROMs do is a little off. There is no BLUE prom.... that is, there are no PROMs for a specific color. The PROMs contain the palette for a set of sprites, characters etc. A single entry in the PROM denotes a single color. If you wanted to blit the color blue to the screen you would use one address.... black would use another address, etc etc. Now if you say that after removing the PROM things get fixed, it could be that you are simply removing the PROM that controls the background color for characters. They were incorrectly blue... but since the PROM no longer exists they're now black. (Keep in mind I haven't looked at this section of the video schematics yet... so I'm speculating.... but this is how these systems work in general)

And because you swapped the PROM in question with another one on the board, you basically swapped the entire color palette for that portion of the graphics, which is why the colors completely changed.
 
When I remove color prom 8F (BLUE) Lower monitor and completely leave it OFF the board. Everything is back to as it should.

Not really.... you lost the blue background you are supposed to have for the character section down below. Take a look at the mame screenshot.
 

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Is the Top Blue and bottom blue of a "DIFFERENT" flash for these chips?


Yes, each of the 6 color proms are different and they cannot be swapped around for testing purposes. As you found out, you will get weird color results by moving the proms around on the board.

D
 
excellent explanation! thanks guys! as you can tell I am still very much learning but am enjoying the process
 
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