No video

[shift838]

I have put together a .96 version board and ensured the jumpers are good. I have tried original 9918 ICs that I know are good as well as 2 different F18A GPUs and neither show any video on the screen. I have not built the keyboard yet and I'm using original TI GROMS.

I have swapped out the LS04 and 574's on the board but still nothing.

Any suggestions? Attached is a photo of my board.

[danwerner21]

Ok, so that is all a good start –

First, the basic stuff . . . .
• Verify good voltages on the 9900 (-5 on pin 1, +5 on 2 & 59, and +12 on 27)
• make sure that none of the TTL logic chips are getting hot, if any of them are it is a sign that you have a bad (or fake) chip
• Check the reset line on the 9900 (pin 6) and make sure it goes low (close to ground) on power up then returns to high (close to 5v)
• If you have an oscilloscope or logic probe, check for activity on the address and data busses
• If you have an oscilloscope, check for a ntsc signal on pin 36 of the TMS 9918

If you see all of that – probably need to verify that the ROMs were programmed correctly for the jumper settings you are using.

Also, one way more way to verify activity . . . is there a random sound from the sound chip? One of the very first things that happens after a reset is that the TI sets the sound chip to default values – before that the sound chip will be emitting a tone.

Dan

[shift838]

I do not have an oscilloscope. I'll verify voltages and make sure nothing is getting hot. As far as the ROMs, i am using 27C64 and i believe my jumper settings are accurate. They look like one of your photos as well.

[shift838]

Voltages verified are correct on the right pins. none of my logic chips are getting hot. The 9904 is warm to the touch but not hot, same with the 9918. The 9918 came out of a real 99/4A and the 9904 I bought from Mike Dudeck (another TI guy).