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TI-99/4A Video Issues?


dustfilledhobo
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I'm very new to the TI-99/4A so please bare with me.

 

When I use the RF Box to connect my TI-99/4A to an old TV I get a picture and everything looks "great" (the picture quality of both my TVs is a little distorted, but that's no fault of the TI-99/4A), however, when I connect the TI-99/4A to a Commodore 1702 (in the front) using a 5-pin din to composite video/audio cable I can get sound, but no picture (black screen).

I've tested the cable with my C128 and it works great and I've also tried another non-commodore monitor that I own that only takes composite video/audio.

One more thing, when connected to the RF everything acts normal, but when I connect using the composite cable, the computer often gets stuck on little intro beep of the TI-99/4A. It almost sounds like an old telephone ring, with no breaks in between the rings. Other times, (when hooked to composite) it seems to operate normally (as far as I can tell with out being able to see the visual output).

 

Any suggestions as to what I'm doing wrong or what I could try to fix this? Thanks!

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the TI is weird about the AV cable you use- it might be wonky for the TI (but works ok for the C128).

 

Interesting, the pins according to the diagram below suggest it should work, but you're saying that a faulty cable might work on a C128/C64, but not the TI-99/4A.

 

So the TI-99/4A is more particular I guess?

 

I think I'll just build my own cable using the diagram below. Can someone please verify that these are correct? Thanks!

7896.png

 

Sounds like a bad cable to me maybe incompatible

 

Sent from my LG-H830 using Tapatalk

 

Thanks for the quick reply

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http://www.mainbyte.com/ti99/hardware/cables/cables_page.html

 

Sent from my LG-H830 using Tapatalk

Thanks! I'm leaving this here so I can find it easier:

m_cable.jpg

Is it a cable with 2 or 4 RCA connectors? Do you have a multimeter or other continuity test equipment to ensure that each pin on the DIN only leads to max 1 RCA plug, except pin 2 that is ground and should lead to the outer shell of all RCA connectors?

2 RCA connectors. I never thought about multiple pins being connected to the same RCA connector (either by design or through a short), I'll test the cable with my multimeter when I get home today. Thanks for the suggestion!

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Is it a custom cable for computers, or some general purpose cable? I believe in some audio applications, pins 3+5 and 1+4 might be wired in those pairs.

 

I don't know what effect it would have on the C64 to wire together luma and composite video outputs, perhaps a washed out signal. I would avoid to wire together the audio out and audio in as it might damage the SID, but perhaps it doesn't do anything bad.

 

On the TI-99/4A in that case you would be wiring together audio and N/C which should be safe, but also wire together composite video with 12V that probably not is a good idea either for the monitor or the computer.

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Is it a custom cable for computers, or some general purpose cable? I believe in some audio applications, pins 3+5 and 1+4 might be wired in those pairs.

 

I don't know what effect it would have on the C64 to wire together luma and composite video outputs, perhaps a washed out signal. I would avoid to wire together the audio out and audio in as it might damage the SID, but perhaps it doesn't do anything bad.

 

On the TI-99/4A in that case you would be wiring together audio and N/C which should be safe, but also wire together composite video with 12V that probably not is a good idea either for the monitor or the computer.

I bought a C64 lot locally (C64, monitor, disk drive, games, etc.) and this cable came in the lot. It looks mass produced, so I think that it isn't custom, but it is possible that it wasn't intended for a C64 specifically.

 

It has 1 yellow and 1 red RCA connector and a 5 pin DIN on the other side. The first odd thing about it is that the yellow is AUDIO and the red is VIDEO (definitely not the standard in the US.... maybe elsewhere?).

 

Anyway, I haven't had time to build my custom cable, but I did a quick check with my multimeter and got these results:

 

The audio RCA is grounded correctly and the tip is connected to the audio pin like it should be, however, the video RCA connector connects to both the video pin and the 12V pin (I'm lucky nothing got fried!)

 

So that means on the C64 the composite video and S-video luma are connected when using this cable... it doesn't seem to have that bad of an effect on it, but I'm more of a sound guy than a visual guy anyway... so I probably wouldn't notice a difference.

 

ah cool. so I could add this to my small compendium :)

 

 

attachicon.gifGENEVE-9640-&-TI-99-4A-&-MONITORS-PINOUT-v16.pdf

That's a cool little sheet you have there... I might hold on to this.

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I built my cable and everything WORKS! Thanks for everyone's help!

 

Also, I tried the cable with my C128 and it is a lot brighter... that composite + luma was washing it out quite a bit apparently.

 

I remember buying a mass produced cable back in the 80's to hook up to a Ti-99/4A with a Commodore 1802 composite monitor. The cable was labled Commdore or TI compatible and it worked great and looked good on the monitor too.

 

I got a lot of ribbing about having a commodore monitor on a TI-99/4A.

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I was trying to figure out what your first cable might be useful for. It can't be used with a VIC-20 as it would tie Video Low (composite video) and +6V in a similar fashion that you tied Video and +12V on the TI-99/4A. It can't be used with a Sega Genesis as it would tie Audio with +5V and on the other plug connect the Green component of RGB instead of composite video.

 

Perhaps an audio application. I see on Pinouts.ru that pin 1 usually refers to left channel and pin 4 to right channel. If it was a tape recorder, tuner etc outputting a stereo signal to a mono amplifier, perhaps they would tie the two pins together, and then accepting a mono input return on pin 5 (right channel).

 

In any case, good that you solved the mystery and no equipment got damaged! I usually always check unknown cables before plugging them in to be sure. Of course if you got it in a computer lot, you may have expected it to be custom made for the computer but don't trust anyone as they say.

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I was trying to figure out what your first cable might be useful for. It can't be used with a VIC-20 as it would tie Video Low (composite video) and +6V in a similar fashion that you tied Video and +12V on the TI-99/4A. It can't be used with a Sega Genesis as it would tie Audio with +5V and on the other plug connect the Green component of RGB instead of composite video.

 

Perhaps an audio application. I see on Pinouts.ru that pin 1 usually refers to left channel and pin 4 to right channel. If it was a tape recorder, tuner etc outputting a stereo signal to a mono amplifier, perhaps they would tie the two pins together, and then accepting a mono input return on pin 5 (right channel).

 

In any case, good that you solved the mystery and no equipment got damaged! I usually always check unknown cables before plugging them in to be sure. Of course if you got it in a computer lot, you may have expected it to be custom made for the computer but don't trust anyone as they say.

Yeah, I'm going to check the pinouts of all my cables before using them in new applications from now on, even if I think I know their intended use. Thanks for your help!

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