Amiga 3000 video issue

[JamesG]

Hi, interesting case here on a rescued Amiga 3000.

It did have some battery corrosion, and I removed the battery and cleaned up with vinegar and then alcohol.

First problem was that on the VGA port, the video was quite jittery. It's a NEC 1970 LCD which works fine with my Amiga 500. So it works, just doesn't stay still. The 23 pin port didn't work at all.

I cleaned the corroded areas again, and then switched jumper J481 to 1-2 in case its previous setting was causing video output to only go to VGA port.

Now what it does is provide no video at all to VGA port, even with J481 back to 2-3.

However...and this is the weird part...I can only get a display out of the 23-pin port and it only works if I turn it on first connected to VGA, then unplug it and plug it in to the 23-pin port via adapter. It will not work otherwise. But it is rock solid display when it gets to that point.

I'm thinking my cleaning might have obliterated some traces, or the extent of the corrosion might have damaged something. In particular something associated with the VGA port might be causing a fault now.

Any suggestions on where to continue work?

Thanks

[Acill]

I seem to remember a pot you could adjust for the A3000 VGA port. It certainly sounds like its off a bit at least from the early issue you had. As for the other issue I would double check the caps in the area and make sure the jumper pins are clean and not corroded at all.