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An Odyssey 2 Journey to Composite Video Heaven


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Back in August 2018 I started a long journey to get my Odyssey 2 unit not only working, but to also get as good a composite video output as I could get. When I first hooked this unit up to my Sharp LCD TV (the only display I have that handles RF and composite video signals well) I had issues with wrong/missing colours being displayed (both with RF and composite).




This was solved by replacing the faulty IC1 Color Encoder (612160-3) with one from a donor O2 motherboard that I got from @masschamber. This got all of the colours working :thumbsup: :thumbsup: :thumbsup:




But I wasn't happy with the quality of the RF image and so my journey began to figure out which was the best composite video mod available. There appeared to be a number of options but I couldn't find any comparisons between them all and the costs were rather high to buy available preassembled mods and to try them all. So instead, I decided to design my own PCBs and to build my own.


After quite some time, I'm now pleased to announce that I've received, and tested, my PCB designs for what appears to be the two most popular composite video mods for the Odyssey 2. I refer to these two different mods as Type 1 and Type 2. In addition, there is also the basic raw composite video mod which I call Type 0. I've tested all three of these composite video mod types using the same Odyssey 2 and TV setup and provide a visual comparison of the results below. But first, a brief description of what each of these mod "Types" are.

  • Type 0 : Simply takes the raw composite video signal from the O2 mainboard without any further processing. Many people report that this creates a dark image (including myself) even after adjusting the on onboard trimmer.
  • Type 1 : Uses two transistors to amplify the raw composite signal from the O2 with the image brightness being adjustable using a small potentiometer. Commercially this mod is available from RetroFixes for US$22 to 28 + shipping.
  • Type 2 : Uses a single transistor to amplify the raw composite signal from the O2 and is characterised by the mod using four electrolytic capacitors on the video side of the circuit. There is no adjustment for image brightness in this design. Commercially this mod is available from Cool Retro Projects for US$32.40 + shipping. The same seller (retro_mood) also has this listed on eBay for US$24.70 + shipping. This seller/mod is often referred to as the Turkish one as the seller is based in Turkey.

The Results


The following are comparison images that I have put together for each of the three "Types" of composite video mods that I described above. I recommend viewing these images at full size to see the detail.


post-5757-0-97996000-1554755747_thumb.png post-5757-0-49781100-1554756528_thumb.jpg post-5757-0-95986400-1554756091_thumb.png


post-5757-0-20724900-1554756622_thumb.png post-5757-0-92799000-1554756664_thumb.png post-5757-0-21350000-1554756746_thumb.png




Type 0 - the image quality isn't terrible but on my TV it is much darker than is apparent from the photos (I'm assuming the auto exposure on my camera is making them look brighter than they actually are). I've tried adjusting the Video Brightness via the variable resistor on the O2 motherboard but increasing the brightness just washes the image out and leads to instabilities (flickering). The best image I can get has grey instead of white. Other colours are strong, but over-saturated, with both purple and blue looking poor and bleeding towards white. The definition of individual pixels is poor often with one pixel blurring making shapes look blurry or just plain wrong.


Type 1 - after adjusting this with the mod's potentiometer, in my opinion, this gives the best overall image quality in terms of colour definition and pixel sharpness. While red looks more like a deep pink, all other colours are well defined, while not over-saturated they are perhaps a little under-saturated. Both purple and blue look good. The moving round block barrier in Alien Invaders looks green (as opposed to the other two which are both too dark), and the explosion is very sharp and well defined. KC Munchkins sprites look great compared to the other two options which look decidedly worse. The Winner !!!.


Type 2 - this provides a pretty good image but is unfortunately let down by being a little too dark (again not always clear from the photos). Perhaps some adjustment of resistor values might solve this but unfortunately this mod does not come with a potentiometer. In some cases colours are better than the Type 1 mod, but with other colours they are over-saturated, e.g. blue and purple again which can bleed towards white depending on what is being displayed. Pixel sharpness is greatly improved over Type 0, but is not up to the quality of Type 1.


This comparison is purely subjective and is specific to my hardware (TV) setup. Your results may be different based not only on your specific TV (and in particular if it is a CRT or a more modern TV) but also on your personal preference. For me and my setup, Type 1 is my composite mod of choice.


PS - I'll follow this topic up with another providing details of the Type 1 and Type 2 mods and the PCBs I designed (these will be shared on OshPark). I also have some spare assembled boards that I'll be looking to sell on at cost.


And on a parting note, here's an image of the full screen of KC Munchkin using the Type 1 mod. I think it looks awesome.



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