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O2 Video Issues - Wrong/Missing Colours - Help Needed


Ikrananka

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Quite a few years back I picked up a beat up and very dirty O2 for cheap from a local seller on Kijiji (including over a dozen games). It's only now that I've gotten round to actually trying this unit out. While the console functions, i.e. with a cart I get the SELECT GAME screen and can start and play a game, unfortunately the colours are wrong. The picture below gives a good idea of what I mean. As you can see there is no yellow or red displayed.

 

I have checked the voltages at the mainboard from the original power supply and get 13.6VAC when the console is off, and this drops to around 12.0VAC when it is turned on. I'm guessing this is okay as the power supply states 11.5VAC output - am I correct?

 

I have also tried two different RF cables with no difference.

 

Note that this unit has no video mods (or any other mods) and so I'm setting this up to my TV using RF. I may do a video mod to this unit later but would at least like to get the colours working correctly via RF beforehand.

 

I plan on reseating the two socketed chips in the mainboard and replacing all of the electrolytic caps but have low confidence that this will make any difference. Any suggestions as to what may be causing this are gratefully received.

 

post-5757-0-60925000-1534279022_thumb.jpg

 

 

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On those old power supplies, as you guessed, the input voltage is indeed very variable - a more extreme example is the Atari 2600, which is rated for 9 volts, but because power supplies got more powerful over time, it usually receive 12/13 volts (which is a reason why the voltage regulator end up failing).

Anyway, for your problem....

 

hs_Odyssey_091.jpg

You will want to check the video controller.

The Odyssey2 feed composite video and sound to the RF emitter. From my own experience, fiddling with RF box is only prone to destroying them. Your issue might be in the RF emitter, but the only way to check that is to do a quick video mod (usually, simply soldering a wire to the composite video signal and hope that your TV will accept the usually faint signal).

 

Else, the issue might be in the video controller, or the circuitry between it and the RF emitter.

https://drive.google.com/file/d/0ByX0R-KjYec7NDU5NmQyNDEtYTU4Ni00M2M4LWE5NDUtYzAzN2RjZTcwMzBm/view?hl=en_GB

 

The Intel 8245 output RGB colors, so you might wanna focus on the RGB part. Chips creeping out of their sockets it not unknow, so your issue might simply be that the chip creeped out and the red pin is out (from the pic, you have blue and green working).

Either that or follow the trace, but, I'll start with pulling the chip out and back in.

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Quick update. I tried the basic composite video mod and get the same result as through RF, so I guess this eliminates the RF box as being the issue.

 

I also pulled the Intel 8244 GPU, sprayed IPA over the socket and did my best to clean it. Re-seated the 8244 but get the same result as before (i.e. no red apparent on-screen). Did this twice - same result.

 

So, I'm assuming that the problem must either be the Intel 8244 GPU, the 612160-3 Color Encoder or the traces between them. I'll check the traces for continuity and will report back.

 

BTW - I also replaced all the electrolytic caps with new ones - no difference. However, I did find one or two of the old caps to be well out of spec and so they needed to be changed. I also checked various locations for +5V DC and got this voltage spot on so the voltage regulator etc. is doing its job.

Edited by Ikrananka
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Finished checking for continuity between the CPU, the GPU and the Color Encoder and all of the direct connections are perfect (zero resistance). I checked from the top of the board at the pins on chips to ensure I was also testing for any cold solder joints.

 

So, looks like I have a defunct Intel 8244 GPU or 612160-3 Color Encoder. Does anyone know where I could get hold of either of these?

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I have a board with both those chips still on it but without the power regulator or CPU. Im pretty sure the 8244 is good but I cant guarantee it.

If you want it I can solder off the big 4700 cap and send it to you. How about $10.00 shipped in the US but again as is.

PM me I interested.

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I have a board with both those chips still on it but without the power regulator or CPU. Im pretty sure the 8244 is good but I cant guarantee it.

If you want it I can solder off the big 4700 cap and send it to you. How about $10.00 shipped in the US but again as is.

PM me I interested.

 

PM sent :)

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  • 3 weeks later...

Update :

 

Did some testing with a friend and this seemed to show that the Red output from the VDP had far lower activity than the G or B outputs. So, this placed suspicion onto the Intel 8244 VDP. Due to the high shipping cost for sending a motherboard from the US to Canada, metarog sent me just the 8244 from his donor board and this arrived today. Swapped it out and unfortunately the problem is exactly the same as it was before.

 

So suspicion now falls onto the IC1 Color Encoder (612160-3). Does anyone have one of these I could buy?

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  • 4 weeks later...

Thanks to AA member @masschamber I picked up a couple of complete O2 motherboards that he was selling for parts. Pulled the IC1 Color Encoder (612160-3) from one of his boards and put it, with a socket, onto my board. Now my colours are as they should be so the problem was the Color Encoder. Here are a few pictures.

 

post-5757-0-82546400-1538511201_thumb.jpg post-5757-0-86626900-1538511215_thumb.jpg

 

 

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