RF modulator problem

TI-99/4A Hardware problems, questions, etc.

RF modulator problem

Postby boblothrope » December 15th, 2011, 10:14 am

I recently tried setting up the old family 99/4A, connected to a TV. The sound comes through just fine, but the screen is totally black.

The RF modulator is connected to a VHF/UHF splitter/300 -> 75 ohm converter, which is plugged into the coax input of the TV.

It's great that I can play Hunt the Wumpus in blind mode (literally), but I'd prefer to be able to see something.

Any idea what's wrong?
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Re: RF modulator problem

Postby Ben Yates » December 16th, 2011, 6:51 am

You hear the sound? What channel is the modulator set to? Make sure the channel on the tv is set the same.

You'd be better off getting a cable with standard RCA jacks for the video and audio, and hooking up through a component (like VCR or DVD recorder) that accepts the inputs to send it to the tv.
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Re: RF modulator problem

Postby boblothrope » December 16th, 2011, 2:54 pm

Ben Yates wrote:You hear the sound? What channel is the modulator set to? Make sure the channel on the tv is set the same.

You'd be better off getting a cable with standard RCA jacks for the video and audio, and hooking up through a component (like VCR or DVD recorder) that accepts the inputs to send it to the tv.


I get these results if the modulator and TV are set to the same channel (both 3 or both 4). If they're set to different channels, I get static.

I found the instructions for making a TI to dual RCA cable at http://www.99er.net/TIvideoadapter.htm . I'll give it a try.
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Re: RF modulator problem

Postby psycho5898 » January 19th, 2012, 5:15 pm

Normally it's a problem with Pin 4. The original modulator has very poor connections to the actual plug. If you're gung-ho on using the stock box, soldering all the connections then covering them in something like hot glue would work to keep them in place. I just made myself a composite cable and called it a day; it's so much easier than trying to mess with tuning the VHF.
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