Video Pinball - Take 2

orion3311

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Well, my Video Pinball is dead again. Its actually been sitting dead but I finally got around to muscling it out of its slot to check it out. It seems the board developed a problem on its own, it has a repeating beeping sound, almost like a stuck key on a computer. The screen appears to be out of sync with a sort of repeated pattern which tells me something is either oscillating, or NOT oscillating properly.

The game was literally turned off at some point, then when turned back on started doing this.

Putting it in test mode, the screen still has a simliar picture, but the button tests seem to work right (makes a pop when pressed), and I don't hear any beeps regarding bad ram.

Anyone have ideas? I believe its the caps on the board just up and failed, so I guess I"ll have to source those out.
 
Have you checked the power supply voltages and reseated the connectors? I'd check those and then replace the caps/verify all of the solder points on the board.
 
I checked the +5 and a couple other ones but I should go through it better. I was looking at the schematic through my iphone and it was hard to read the pinouts.

I may also scope the power supply as I don't think I ever replaced the big blue.
 
Yes check the basic stuff first. Really hope you can get it working again. I've recently got a Video Pinball too. It's in shambles now and will have to wait for other projects but I will go work on it for sure.

http://forum.arcadecontrols.com/index.php?topic=100371.0

Here's some pics of mine if you need help ID'ing what goes where. Someone replaced your Owl Eye with a standard coin door too! Given the age I bet they all came with owl eyes.

http://www.junknet.net/arcade/?g2_itemId=4103
 
Ok as an update to this, I took a few minutes to try to troubleshoot this today. I scoped the unregulated 10v coming from the power supply, and while there was ripple, it wasn't that bad when you actually connected the board. I replaced the big blue anyway and the only difference seems to be a little more voltage. +5v on the board is 5.1 and when scoped its solid as a rock.

In regards to the beeping - its the processor resetting due to the watchdog. When I ground out the watchdog disable, the beeping stops but still no video. The monitor appears to have a repeated raster pattern on the screen.

This leads me to believe that something with the sync circuit is screwed up, although to be honest this is maybe the second arcade board I'm ever trying to troubleshoot myself. I got as far as the Sync Prom and that seems to be getting very hot. Could that be bad? Its the only chip on the entire board getting hot like that. That said, I'm still getting what I'm assuming is normal output - pins 9,10,11,12 all had a signal on them.

If that chip is bad, where would I go about finding one? Its called the "sync prom" in the manual, and has the Atari logo on it, which tells me that may not be fun to find.

Last but not least, lets that chip isn't bad, is it possible this could have bit rot on the roms? This board uses 9316 roms, should I pop those out and verify them?

EDIT: It looks like H4 (location of sync prom) has a file in the mame files. Can I possibly burn a new chip for this? I have a BP Micro PLD-1100.
 
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Found in the mame driver that indeed that file IS the sync prom! Woohoo!

Assuming that since the file size is 256 bytes, and there's only 4 output lines, that this would be a a 256x4 prom, such as a DM74S287N?

Datasheet: http://www.alldatasheet.com/datasheet-pdf/pdf/127016/NSC/DM74S287N.html

Ironically enough it appears the pinouts look the same.

(Been reading a lot the past few days)

Again if there's somewhere else I should look, please let me know, I'm just assuming that since that chip gets pretty hot that it could be bad??
 
Some of the older +5V bipolar PROMs do run warm. I'd say if you can hold your finger on it for a two-count then the likelyhood of it being bad is reduced. However if you leave a skin fingerprint behind then I'd suspect it might be bad! :)

I wish I had more time to help out with this seeing that it's an Atari B/W raster game :) but I'm completely swamped right now.
 
Thanks - its warm enough where I can definitely tell its hot but not hot enough to actually pull my finger away or get burned. Again I do get signals out of all 4 outputs so I'm going to assume its working for now. Also since its the only PROM I guess that could be why its the only chip getting that warm.

I guess my next step is to pull the roms and test? The only problem with that is that the mame file has the files for the 14 proms - how do I figure out which files to combine for the 4 roms? The manual does have a rom to prom table so I suppose I could use a hex editor and apply each prom file based on the rom selection to make an image.

Added: Just found out from a friend, this wasn't turned off that way, it died while we were having a game night one night. I totally forgot that.
 
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Update: EXTREMELY FRUSTRATED.

Well, I mistakingly thought this would be a good learning experience for me, and maybe it has, in that I shouldn't be repairing boards. I didn't actually change any parts, but somehow had a breakthrough and possibly messed up the ram that I installed earlier. I'm tired, burned out, and ready to push this thing in front of a tractor trailer.

Anyhow, here's the scoop. The problem has to be in the sync circuit somehow, the monitor displays 3 columns of raster so to speak, and self test vs game mode doesn't matter. It just doesn't appear to be sync'd, and the sync circuit clocks everything else on this board.

Tried swapping processors - no change.

Originally, the self test seemed to be working blind - I could press buttons and hear the acknowledgement noise. Unfortunately, I tried re-seating the 2 rams I installed earlier, and now I'm getting a ram error on self test. BUT, that proves that the self test was completing before, so that means the ram was good, and the roms are good, the switch input circuits are working, and I'm assuming the processor is also working.

So to sum it up:

A. Processor is watchdogging
B. Self test originally got through ram and rom test even when problem is happening
C. +5v looks clean, big blue is replaced, audio seems to work fine so +18v is good
D. Swapping processors didn't help
E. Monitor displays 3 blank columns whether in game or test mode (sync circuit problem??)
F. Game failed during play
G. Unplugging control panel didn't help
H. Sync prom gets pretty warm
I. Suspecting sync prom, or something in sync circuit.
J. Also suspecting address decoder responsible for ABUS 12/13 (connected directly to CPU and also responsible for watchdog signal).
K. Couldn't get great readings on scope, nor on a frequency counter.
L. Crystal did show 12mhz on frequency counter.

Sigh.
 
OK,

You have a full raster screen when in test mode? Sounds like sync is working. If sync wasn't working then you'd have scrambled screen and a high pitched whine coming from the monitor. It'd look like it does when the horizontal hold is out of whack and the video looks like the sync is rock solid.

You show that it's working enough to register inputs from buttons when in test mode. If it's doing that then the watchdog circuit shouldn't be firing. Can you verify that the watchdog isn't firing when in test mode?

I would start by checking the address/data lines and the enable lines on the ROMs and on the RAM chips. If those are working then replace the RAMs.

If the enable lines aren't working on the program RAMs and on the program ROMs then check the address decoding circuit with a logic probe.

If the enable lines are working then replace the RAMs.

Beyond that you need to break out the logic probe to find the bad chip.

RJ
 
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