Apple ][ Plus ????? on screen @ startup

I had similar problems with my Europlus, and it was RAM.

If you have a language card, remove that.

May be worth stripping out RAM until you only have the base 16K installed. If it works, you can swap out banks to see if you can work out what chips are bad.

I've also had to clean all the legs of half the ICs, but that's because they had a lovely brown tarry look. I just used an ink eraser and isopropyl.

Cheers!

Chesh

If you get a beep at power on, that's a good sign that the CPU, clocks, some ROM and some RAM are working. Make sure you don't have the non-autostart F8 ROM installed. CTRL-B would take you to BASIC if that's installed. It's also possible that the video section is stuck displaying Text screen 2. Type CTRL-G to see if you get a beep.

Next step would be to play with the RAM as CheshireNoir suggested.

jeffmazur wrote:

If you get a beep at power on, that's a good sign that the CPU, clocks, some ROM and some RAM are working. Make sure you don't have the non-autostart F8 ROM installed. CTRL-B would take you to BASIC if that's installed. It's also possible that the video section is stuck displaying Text screen 2. Type CTRL-G to see if you get a beep.

 

Next step would be to play with the RAM as

I encountered this with a bad language card, that I have yet to diagnose. I know for a fact that it was not the RAM on the card, but rather, it is either a failed logic gate or a bad ribbon (that fails to properly refresh the RAM). 

I'm still trying to get one of my Language cards repaired. :-)

I have just replaced the ribbon and checked all the 74 series logic, so I'm hoping it's fixed.

Chesh

row C is bank 0. If you blindly type some keys and press enter does it beep? If so, it's probably not ram.

You need bank 0 ram to read keypresses and do the beep routine. If ram doesn't help, remove all roms except F8

which is all that's needed to clear the screen and get to * A bad rom can cause that ??? hangup too

Larry G