Rev 0 that puts screen full of question Mark's but is unresponsive

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Rev 0 that puts screen full of question Mark's but is unresponsive

Got my first Rev 0!  It's in really nice shape.

When I first powered up, I was getting a solid white screen.  If I powered down and back up again, it would sometimes display a screen full of Gs.

I decided on a strategy of removing the entire chipset, and replacing it with a known good from another Apple II and then swapping in chips one by one until something broke.  However, still had the same problem on power up.  I did find one IC that got rid of the solid white screen on startup.  Playing with memory I occasionally got random screens of characters, some of which were changing.  Ultimately though, when the remainder of the ICs were returned, I now just get a solid screen full of ? marks.  I reseated the memory config blocks, sometimes that would result in things randomly changing, but then back to solid.  Reset and CTRL-reset don't do anything.

 

But yeah.. just ? now.  I'm goin

 

I've checked the RAM, ROMs, CPU etc in the other Apple II.  No problem.   I'm not seeing any damage to the board, no rust.  I'm thinking it might be something still on the board like a transistor.

 

Anyone run into this before?

 

Many thanks!!

 

 

 

 

 

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Joined: Jul 5 2016 - 19:01
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You could have a poor socket

You could have a poor socket connection issue which is why your still getting the same problem after you swapped the entire chipset.

You probably need to use a scope or probe to narrow down the problem.

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Okay, so I learned this: don

Okay, so I learned this: don't trust that one of your other Apple II's keyboards is working properly.  Apparently reset wasn't working on it, so when I was testing with the Rev 0 and not getting any reset, I assumed the Rev 0 was at fault.  I finally borrowed one from my II+ when I realized Reset wasn't working on the Rev 4 it came from either.. voila, we have monitor prompt!

I'm curious - is it in fact normal for a Rev 0 to power up in full graphics mode?  It does this to me often - I'll get a full screen of white, or random color bars.  When you hit reset, they change into alphanumeric characters.  I'm just wondering if this is indicating a problem I'll have to tackle elsewhere.  At some point when I was swapping ICs around, this went away, and I had a solid screen of ?s.

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