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Ti-99/4a issue

New2vtgpc

Experienced Member
Joined
Oct 22, 2019
Messages
122
Location
Iowa
So I finally got around to tearing apart and testing my ti, (making a restore vid) and ran into an issue. Upon power up, only static woth a light buzz. I removed and resocketed the video, grom, and sound chip with no change. All chips seem to have voltage and ground at the correct pins. But nothing has changed, only outputs static and a buzz. The buzz changes pitch when key pressed.
I'm leaning towards the video chip being bad, but wanting to hear from someone that had similar issue.
 
So I finally got around to tearing apart and testing my ti, (making a restore vid) and ran into an issue. Upon power up, only static woth a light buzz. I removed and resocketed the video, grom, and sound chip with no change. All chips seem to have voltage and ground at the correct pins. But nothing has changed, only outputs static and a buzz. The buzz changes pitch when key pressed.
I'm leaning towards the video chip being bad, but wanting to hear from someone that had similar issue.

I am far from being an expert, but I have watched lots of youtube repair videos. If you can get a known good video chip, that would be a reasonable plae to start, since it is the only socketed chip. If that isn't it, you probably need to get an oscilloscope and start checking activity on address, data, and chip control pins to try to narrow it down. You did check all three voltages? Also, leaving it on for a while and checking the ram chips to see if any are extra toasty might indicate a bad RAM.
 
I am far from being an expert, but I have watched lots of youtube repair videos. If you can get a known good video chip, that would be a reasonable plae to start, since it is the only socketed chip. If that isn't it, you probably need to get an oscilloscope and start checking activity on address, data, and chip control pins to try to narrow it down. You did check all three voltages? Also, leaving it on for a while and checking the ram chips to see if any are extra toasty might indicate a bad RAM.

Yep. I checked all those. I didnt have an oscilloscope but set my dvom to hz and looked for frequency.
No change...until I set my meter down on the rf cable on the back and picture showed up. Someone previous attempted a repair...but stripping wires, wrapping around the din pins on back and hotgluing them in place....
Soldered it right and works like a charm.
Oh and on the biege models the grom and sound chip socketed as Well
 
Great. Glad you got it working. I hate coming along behind someone who did a lousy repair. A lot of time undoing what they did is harder than doing the repair right.
 
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