Omega Race PCB repair #2

omegaman

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Ok I have another set arrive today that has been sent over for repair by IFKZ

The main board looks very clean, the sound board looks like its been in a fire :)

IMG_0909.jpg


IMG_0913.jpg


I pulled all the chips that were in sockets, 10 of the Ram were dead

IMG_0912.jpg


The CPU checked out good as did the program Rom.

The video Rom failed (bad checksum).

I installed new Ram and Rom and powered it up using a spare sound board. It passes self test now but the picture on my scope showed a flat line across the screen. One of the 4016's in the vector output stage had been changed...I swapped it out and got a full screen........of garbage. You can play a game and there is movement but it is very corrupt. Swapped the Dac's ...no change so it looks like something wrong pre DAC but not far enough back to trip the watchdog.

I will have a prod around the board later and check a few chips, then time to clean up the old sound PCB.
 
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I saved this from a lset of Omega Race PCBs I bought many years ago when my original sound board blew out. Of all of them, the main board seemed like the most repairable, it was actually very nice aside from the mask lift. I made it as complete as possible using scraps from the other sets. When I got it, it was missing the pots, crystal, DACS, all of the RAM, etc.

I remember being a little unsure if the top socketed chip by the battery was correct at the time, the part number was very faint.

I am very grateful for omegaman's efforts. I never found anyone that was even willing to look at it before he started his repair logs here. It was worth sending it out just to finally answer the question...is it repairable?

If this goes well, I may be on the lookout for a cocktail Omega Race to adopt :)

And please keep the soundboard, it is yours, I figured it would help with voltage checks if anything. It did not cost anything extra to include in the package.
 
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Update on this board.

I had a prod around and found some odd looking signals on K2 (7442) the logic comparator reported this IC was good so I checked the next IC back, a 7483 at J2. The comparator reported this IC had a problem. see image below.

IMG_0915.jpg


note the led's lit for bad outputs.

I removed the IC and checked it in my IC tester.

IMG_0916.jpg


Sure enough it was bad. I fitted a socket and another 7483. Powered it up and it plays perfect!!!

IMG_0917.jpg
 
Having played the game for a while now I've noticed it runs faster than normal.....probably twice as fast. Being similar to Asteroids I'm guessing its a problem with a 74161 so will check it out. It's like the 2x speed up mod on asteroids.

If you want to speed up your Omega race then I could let you know how to do it.
 
Having played the game for a while now I've noticed it runs faster than normal.....probably twice as fast. Being similar to Asteroids I'm guessing its a problem with a 74161 so will check it out. It's like the 2x speed up mod on asteroids.

If you want to speed up your Omega race then I could let you know how to do it.

Twice as fast eh? My game is not sped up but I do notice some lag a few levels into the game, when the number of enemies has increased. I wish I knew how to supercharge the game so it ran normal speed even as more enemies are encountered.

This seems to be a normal problem with the older vector games I've noticed. Space Duel has a similar issue, but it seems to deal with it by allowing some of the larger "asteroids" to simply POP out of existence when you shoot it, instead of splitting into smaller entities. Star Trek SOS also starts to lag on the higher levels, which can be a real drag.

M.O.
 
If you cut pin 4 of R6 (74161) and connect it to R156 1K ohm (not the +5v end of r156, the other side so it acts as a pull up) That should speed it up x 2. You could fit a switch so that you can select between normal and x2.
 
Wow... I may have to try that out. I'll bet level 3 and 4 would be a hell lotta fun that way. :)

Thanks for all these great Omega Race posts! :beerchug:
 
Wow, an undocumented speed up hack for Omega Race. Who would have known! I am amazed, speechless really that it is working!
 
Update on this board.

I had a prod around and found some odd looking signals on K2 (7442) the logic comparator reported this IC was good so I checked the next IC back, a 7483 at J2. The comparator reported this IC had a problem. see image below.

IMG_0915.jpg


note the led's lit for bad outputs.

I removed the IC and checked it in my IC tester.

IMG_0916.jpg


Sure enough it was bad. I fitted a socket and another 7483. Powered it up and it plays perfect!!!

IMG_0917.jpg

Omegaman, you got some neat toys :D
 
I don't know if everyone here sees how cosmetically bad that board looks. Look at the green mask, it is flaking off almost everywhere. It had a lot of prior work done to it with ten or so new sockets. I had no way to check if this work was good or not. If you flip it over there are a lot of soldered areas. That more chips were not bad is amazing.

The board was sent through the dishwasher and left in through the heat cycle as near as I can figure.

Amazing! Look at what omegaman has done!

I saved it for several years because I had hope it could be fixed because the traces all looked very good, especially in the commonly damaged area where the battery used to sit.

I hope this helps save a couple more boards....it goes to show that what may not be repairable at the time is still very much worth saving.
 
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You forgot to mention it was flown 4,000 miles packed in a plastic bag 


I don't know if everyone here sees how cosmetically bad that board looks. Look at the green mask, it is flaking off almost everywhere. It had a lot of prior work done to it with ten or so new sockets. I had no way to check if this work was good or not. If you flip it over there are a lot of soldered areas. That more chips were not bad is amazing.

The board was sent through the dishwasher and left in through the heat cycle as near as I can figure.

Amazing! Look at what omegaman has done!

I saved it for several years because I had hope it could be fixed because the traces all looked very good, especially in the commonly damaged area where the battery used to sit.

I hope this helps save a couple more boards....it goes to show that what may not be repairable at the time is still very much worth saving.
 
This board is good to run for a few hours now. The speed issue was down to a faulty 7474 at H9...the speed at the INT pin 16 of the CPU was running at around 900khz....should be nearer 300!. The output of S6 7404 looked good so that was the only IC left in the chain.
My logic comparator and IC tester both tested the chip good......I swapped it out anyway just to see if it made any change to the speed, it runs at normal speed now.
Time to play!!
Parts used:
10 x 2114 Ram
1 x 4016 @B6 (flat line on the screen)
1x 7474 @H9 (speed too fast)
1 x 7483 @J2 (messed up size and shape of objects)
1x 14 pin socket.
2 x 2716 Roms (someone had installed 2732's)
Roughly 4 hours work.
4 cups of coffee. :)

would you like the old 7474? you could stick it back in the socket if you want a 3 x speed up mod!!!
 
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