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Solid Grey (Not Black) Screen


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So I recently got a PAL C64 bread bin that gives me nothing but a grey screen.  

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This is a 250425 board with several small modifications compared to my two other 250425 boards. Unfortunately, I'm not experienced enough to know whether their normal or not.  

All the ICs on the board were soldered to board except the SID, VIC II, and Clock.  I desoldered, socketed and replaced the PLA with a PLAnkton to no effect.  

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The VIC II is a 6569R3.  This is the only PAL version I have, as all my other boards are NTSC, so for the moment, I can't swap the VIC.

I did try this without the SID.  No difference.  

So far I can eliminate the SID, PLA, Video Cable, and Power Supply (Ray Carlson model, tested with 3 other working NTSC C64s).  

 

Sadly my Dead Test is dead at the moment (ironic, I know) so I haven't been able to run any diagnostics so far.

Any suggestions?

 

Edited by DistantStar001
additional information.
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Those diodes are fine- they protect the serial lines.

 

My guess is going to be the VIC. You can actually put an NTSC VIC in there for testing and you should get a picture, just at a very odd frequency your monitor may not display properly. You should be able to discern the output though..

 

 

Edited by R.Cade
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24 minutes ago, R.Cade said:

Those diodes are fine- they protect the serial lines.

Thanks!  It's good to know what those do.

24 minutes ago, R.Cade said:

My guess is going to be the VIC. You can actually put an NTSC VIC in there for testing and you should get a picture, just at a very odd frequency your monitor may not display properly. You should be able to discern the output though..

Excellent guess!  I stuck in my spare VIC and got a normal startup.

 455777613_ScreenShot2020-06-08at7_54_48PM.thumb.png.619977a9b4104a8d07952d1dd80a6202.png

 

I'm guessing that I'll have to get a PAL VIC for full compatibility.

 

Additional Thanks and Info!!!

 

Just tested it with the SID and original PLA!  Everything works!  Thank you so much, now I can play all of those PAL games I always wanted to on real hardware!!!

Edited by DistantStar001
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6 hours ago, R.Cade said:

Yes, without changing the crystal and jumpers, you'll still have a PAL-frequency C64 with NTSC video, so it will have poor compatibility. If you intended to have a PAL C64, you'll need a replacement 6569 chip.

Already ordered.  Now all I need to do is figure out how to clean up this awful case (seriously, there are whole lot of melt marks all over it), and find some replacement key caps for the missing ones (I have the 1 key, but it snapped off from the plunger so I need to get the broken plastic out of that too). 

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But at least it works!!!  Thanks again!

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Sure thing. Those marks are from having cables wrapped around it or sitting on it. Over time, the softeners used in the vinyl cords melt the plastic on the case when they sit wrapped around it. It looks almost like cigarrettes were left burning on it sometimes, but it's not from that - different kind of "burn".

 

 

Edited by R.Cade
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