TI99/4A no video signal

[repetto74]

hi guys,

I have an issue with a TI99/4A. I had to open it to apply some thermal paste on some chips but when mounting back and testing I had a garbled image. I was suspecting the metal shielding was shorting the extra RAM chip piggybacked on top of the TMS9900 (Tursi mod) but the suddenly all went black and now I just do not have a video signal at all. No black or blue screen but just "no signal". the power led is turning on but that's all. That's really stupid from me and now I do have fried something for sure. I have soldering skills and tools but need maybe someone to point me out where to look at now.

What can be the main cause of a total absence of video output ?

The only check I did was to ensure that the main PSU and the modulator were ok by plugging them to a working Ti99 and they do work.

thanks

Rick

PS : I gave a check at the power supply PCB and do have correct voltages of +5V, -5V and +12V.

Edited March 4, 2018 by repetto74

[repetto74]

OK guys it is solved luckily!! It was just a bad contact with a chip. A good cleaning solved it.