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Composite Video Mod (in console)

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Does anyone know how to make a composite video output (and audio) mod directly in the TI99/4a console instead of modding the RF Modulator? This would be primarily for a PAL system, don't know if it would be much different for an NTSC system.

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Tricky to get PAL composite video I think as none of the VDPs directly output a PAL composite signal - you've always got to mix the VDP outputs to make a composite signal. (Unlike the TMS9918 which outputs an NTSC composite signal). Wondering if there's room to mount the RF modulator PCB (with the big ASTEC modulator box removed if necessary) directly in the console (sticky pads and insulation on the motherboard shielding) and pick the composite signal off of that?

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Does anyone know how to make a composite video output (and audio) mod directly in the TI99/4a console instead of modding the RF Modulator? This would be primarily for a PAL system, don't know if it would be much different for an NTSC system.

 

NTSC puts out composite on the 5pin din..

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This question is a frequent one, and sadly, there is no (inexpensive) way to obtain composite or rbg from a PAL console. TI produced their European model to give a video output that could be used with an external RF modulator for either PAL or SECAM tv systems.

 

The result is a console output that is very nearly unique- monitors for the ancient Tatung Einstein could be plugged in but otherwise you had to make do with monochrome or tv rf.

 

TI users in the UK have a few choices- find an analogue PAL tv set (getting hard), buy an F18A mod board, buy an NTSC console (and a 230v-110v transformer), or use a mono monitor.

 

I have heard that someone with a plastic SIEL 99/4a PAL rf modulator was able to take a monitor feed from the modulator- the attached image needs more explanation but I can't find anything relevant.

post-47425-0-17257900-1546269151.jpg

Edited by blackbox

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[...] I have heard that someone with a plastic SIEL 99/4a PAL rf modulator was able to take a monitor feed from the modulator [...]

 

yes, it is possible to manage the composite signal from the modulators, here you can find step by step guide we created some years ago for doing the modifies:

http://www.ti99iuc.it/web/index.php?pageid=119&pagina=mod_proj1&sezione=4&data=Mod_and_Tuneed

 

i think it is the easier way to obtain a composite signal from a PAL TI99.

 

without the modulator you can just use some converter from Component YUV2 to Composite.

 

 

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One note on using an NTSC console for this--you don't really need to use an additional transformer. Just plug your European external power supply into the console, as the output from it is the same as the output from the US version--it already does the necessary step down for you. The console's internal power supply is the same in both versions.

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yes, it is possible to manage the composite signal from the modulators, here you can find step by step guide we created some years ago for doing the modifies:

http://www.ti99iuc.it/web/index.php?pageid=119&pagina=mod_proj1&sezione=4&data=Mod_and_Tuneed

 

i think it is the easier way to obtain a composite signal from a PAL TI99.

 

without the modulator you can just use some converter from Component YUV2 to Composite.

 

 

 

It seems this is my final option, iv'e tried making a din to component cable (the output is stripey on my lcd tv as was the same as your cable Ciro), I also bought a converter box to see it that would help - it didn't. The only problem I have with the composite mod for my plastic modulator box is it looks a bit Heath Robinson, but hey if it works .. it works, so I'll look to get some components to do the mod and get it sorted.

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One note on using an NTSC console for this--you don't really need to use an additional transformer. Just plug your European external power supply into the console, as the output from it is the same as the output from the US version--it already does the necessary step down for you. The console's internal power supply is the same in both versions.

 

I have a feeling that it would be better to use an NTSC console with a UK PSU as the games would all run full speed or is this not the case?

Edited by OX.

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The power line frequency may be the limiter here: US power is 60 Hz, while European power is 50 Hz. I suspect the US console would slow down some (and I really should have tested this during the 13 years I lived in Germany), but it really depends on where it is drawing the operating frequency from.

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Speed isn't going to be derived from the AC frequency, as it isn't stable enough or fast enough(and power is converted to DC before it hits the logic board). The 4a has an internal clock crystal for timing.

 

The traditional speed difference between America and Europe is from the slower TV frame rate, but in the modern era, european TVs can take the faster american inputs and now 60 Hz rules the world.

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Speed-

Program speed of execution was more or less the same in all consoles, but there were differences between individual consoles, possibly due to minor component variability or minor changes to the OS or hardware- TI were always tweaking it.

 

The problem in Europe was that a program eg FOR T=1 TO 1000 :: X=X+T :: NEXT T would tend to take the same time BUT the European sprites, controlled by the European VDP and the slower required frame rate, did not travel so far as on US consoles within the same time period. This was a very real problem and required American Extended Basic games sold in the UK to be recoded as jumping games sprites would not jump far/high enough and tend to have collisions. Games where sprites movement was not automated (machine code games often moved sprites manually) were not a problem.

 

UK tv sets can be 100 fps or higher today and all handle 60fps well, but European transmission is still usually 25fps interlaced (25i) (PAL standard) due to bandwidth constraints - although the BBC have demonstrated true 100fps transmission (higher rate displays use interpolation) and some Sky broadcasts are 50fps. The displays are now more flexible than of old, and can handle 60fps or 75 fps or higher well- some Blue Ray disks go the other way and output at 24fps (old movie rate). An advertised 600fps display is using interpolation- there isn't enough bandwidth to handle 600fps transmission especially at 4k definition.

 

 

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All my games need an NTSC or F18A console to run at the intended speed because I'm using vsync for timing. Sprite collision, however, still works on a PAL console. I'm using an NTSC console myself with a European power supply.

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All my games need an NTSC or F18A console to run at the intended speed because I'm using vsync for timing. Sprite collision, however, still works on a PAL console. I'm using an NTSC console myself with a European power supply.

 

I don't suppose there is any simple way of running a pal system at the same speed as an NTSC system, like a timing crystal change? I'm guessing you'd need to replace the VDP also.

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I don't suppose there is any simple way of running a pal system at the same speed as an NTSC system, like a timing crystal change? I'm guessing you'd need to replace the VDP also.

 

I think you can replace the TMS9929A VDP with a TMS9928A and get 60 Hz. But if you connect the output to the RF modulator I guess it won't work or it won't be PAL any longer.

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