Omega Race - sound & video issues

scottmaggie

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Hey guys (and especially you Omega Man!) any help here is very much appreciated...

I picked up a free particle board box full of leaky old batteries and wires mixed with circuit boards better known as: Omega Race. I had fixed one a few years ago so am trying to tackle this one myself too. The story so far...

1. Cleaned the boards
2. Replaced all 14 rams installed 11 new sockets
3. Replaced S1, R1, PR1 with socketed - 741LS245, 74LS32, 74LS04
4. Jumped about 20 bad traces from the various RAMs
5. Checked the voltages at the power supply

At power on:
1. Enters game mode with graphics garbled/squished down to about 1/4" on the bottom right of the screen but just big enough to tell you are firing, moving, etc. Moving the pots on the main board moves the graphics L/R or U/D but still just a thin line about 1/4" high.

2. There is no sound but the amp seems good (touch back of it and get loud hum in speakers, can raise & lower with pot adjustment)

3. Test mode is not flashing any LED errors (It was flashing 10,11,12,13,14 when I started this project so getting this far is huge!)

So I guess I have 2 issues to tackle - no appropriate sounds and the squished video. Any thoughts or suggestions?

:0)
 
update...

OK no more LED flashes! (well except for free play!)

A couple of bad solder joints later and I have more of a picture but still a mess. You can see the game playing and tell all the controls are working. The image is still very jumpy and squished. See photos.

Also still no sound. The power supply is reading 12.05v but at J3 pin 9 it's reading 11v? I am wondering if the sound Z80 or the two AY38912 are bad?

Any suggestions?
 

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OK no more LED flashes! (well except for free play!)

A couple of bad solder joints later and I have more of a picture but still a mess. You can see the game playing and tell all the controls are working. The image is still very jumpy and squished. See photos.

Also still no sound. The power supply is reading 12.05v but at J3 pin 9 it's reading 11v? I am wondering if the sound Z80 or the two AY38912 are bad?

Any suggestions?

sorry Womble...I know this sounds "daf"

I have a personal vendetta against Zilog z80 cpu's! None of my boards will ever have them installed. These are the first chips and sockets I replace.

I bought a Street Fighter II Turbo with no sound and a Zilog z80 chip. Well you guessed it, I replaced the z80 chip and now it works.

just pay close attention to the part numbers
z80
z80a
z80b I think it is the fastest.
 
more progress

I tried swapping Z80's with known good ones. It's definitely not the Z80s.

As for the sound:
I am pretty convinced the AY38912's are bad. I can swap them around and move the garbage noise from speaker to speaker.

The video:
I can touch the 4016's and make the image larger though still garbled. I am going to replace those next (Though I can't seem to find a source for them - anyone?).
 
Progress!!!

Hope everyone had a great turkey day! Got parts today from Bob Roberts, Mark Capps and Twisty Wrist and...PROGRESS!

1. Sound is back! 1 of the AY38912's was no good. Also the Z80 on the sound board was no good (You were right kb0jjn!)


2. Replacing the 4016's, tl081's and tl802's made the image full screen and no longer jumpy but...

The graphics are still scrambled. What's next guys? The video ROMs?
 

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roms...

Not yet. I have no means to do that. What do you recommend for chip testing? You'd think after 15-20 years I'd have one by now...!
 
I use one of these a True-USB PRO GQ-4X Willem Programmer. They are cheap, connect via USB (no hassle with parallel ports) and so far they've worked for everything that I've tried to do with them. Make sure and use a power adapter with them though. . I've heard results are less stellar if you rely on the USB power to run them.

http://www.mcumall.com

You may get more if you buy it from them via EBay. . one gets you more than the other, but I don't remember which way.
 
So am I correct in understanding this programs ROMs and tests chips?

Yes! You can rip the ROMs and compare them to known-good ROMs from Mame. If they are bad, erase them and reburn them to see if that fixes it. If not, then buy new ROMs and burn them from the Mame rom images.

Also, if you get one of these, make sure and get a UV eraser also for the chips that need UV light to be erased.
 
still stuck...

I will be ordering a chip tester/programmer & UV eraser but hey I'm anxious! Anyone have a clue where to look next?

Please see my last post with photos of the scrambled graphics. Do you think this is a video ROM issue or another chip?

?
 
jumpers galore...

This is why no one wants to work on Omega Race boards! Pictures of the mess of jumpers, new RAMs, new TL081's, TL082's, 4016's & sockets for all...

Oh and a lithium battery with blocking diode too.


I am still looking for advice on the scrambled graphics. You guys think it's corrupt ROMs or other chips? (The LEDs so no errors at all).


PS: Pic 4 shows a backwards cap. That was corrected after I took the pic.
 

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Well... First check to make sure you don't have crossed or shorted address or data lines on those chips you jumpered. That would cause scrambling and depending on how simple the self tests are the RAM tests might not see that.

RJ
 
jumpers

I actually re-did the jumpers 2x and checked it a few times - pin by pin until I couldn't see straight. I guess checking one more time can't hurt.

One other weird thing I noticed is starting a 2 player game it seems to think it's in cocktail mode. Player 2 doesn't work the controls. I adjust the dip switches properly but it doesn't help. This is part of the reason I am suspecting bad ROM's though I guess a crossed line like you suggest could also be the culprit.
 
Tomorrow...

Heading over to Jeff - Orion3311 tomorrow with my boards in hand. He has a chip tester and an OR parts board. I will also have my new set of ROMs in hand thanks again to Mark Capps!

I hope to have some progress updates tomorrow night!
 
update...no update. :-(

Jeff (Orion3311) and I spent out six hours on my omega race boards tonight. While nothing actually got fixed we did rule out a ton of things.

1. Power supply is good
2. Filter & Transformer assembly is good
3. All ram and roms are good
4. All work I did, jumpers, sockets, etc. are good
5. The issue w player two not working is not because its stuck in cocktail mode its a bad chip on the daughter card.

We were unable to isolate my graphics issue at this time (nuts!) though Jeff is convinced it not a logic issue. Oh well more work to be done...
 
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