Experience recap Performa 475 ... no video

[franklyn]

I soldered in/replaced new tantalum capacitors instead of the normal capacitors. Since then, the computer has booted normally from a floppy disk or from BlueSCSI, but there is no video. The monitor shows a frequency that is too high, but everything remains black. I don't think it's a capacitor replacement because I've had something like this before, but after a few keyboard resets, it worked again. I took out the VRAM and put it back in.

measured Hsync, Vsync, Sence0,1,2, they are between the monitor socket and the MEMCJR chip.

3.6V battery is new and good

 

[franklyn]

I added the CUDA reset button S1.

The problem was my two new 512kB VRAM modules from the internet that I had just bought and were suddenly no longer working. With my two old 256kB VRAM modules everything was fine again.

Re-solder the 512kB modules and see if they are OK again or not...

 

[Andy]

Do you have a battery installed? If you don't the 475 will not display video. You can try switching power off and then back on quickly to try and get around this sometimes.

 

[imactheknife]

Would reflow the caps you did and clean board really well. Definitely needs good vram to display anything

 

[franklyn]

... the two VRAM Simms are faulty.

I resolder the Simms and all works again.