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8bitforever
Account closed
Registered: Oct 2009
Posts: 48 |
Black (Blank) screen problem and the PLA EPROM solution
I have the black (blank) screen problem on my C64C.
Many circuits have been replaced and I'm now sure it is the PLA chip (906114-01) that is the problem.
What's your experience of the Ray Carlsen PLA Chip replacement ?
http://www.users.on.net/~clockmeister/other/C64PLA-27C512/
http://personalpages.tds.net/~rcarlsen/tdsweb/EPROMPLA/eprompla..
http://vic20.de/html/eprom_pla_8296_und_c64.html
Is it working without problems ?
What's your real experience on this ?
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ready.
Registered: Feb 2003
Posts: 441 |
what ICs have you replaced? On C64c, most commonly blank screen problem was solved by replacing RAM or CIAs. Have you checked for broken traces? |
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8bitforever
Account closed
Registered: Oct 2009
Posts: 48 |
Tried replacing 74LS258,74LS08,74LS257,74LS139 and 7805.
I have started up the machine without the CIA:s. Still the black screen with the dim vertical lines. The RAM:s do not run hot. This is an old C64C with the PLA chip that´s the most common chip to fail in a C64.
So I'm very intrested to hear about real EPROM PLA stories ...
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lemming
Registered: Oct 2009
Posts: 44 |
I've tried it (Ray Carlsen's), it works.
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8bitforever
Account closed
Registered: Oct 2009
Posts: 48 |
How many nanoseconds is your EPROM at ?
And you have found no bugs at all ? |
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lemming
Registered: Oct 2009
Posts: 44 |
150, no problems so far... It's a TMS 27C512-15JL
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8bitforever
Account closed
Registered: Oct 2009
Posts: 48 |
How long have you been testing it now ? (days)
Why didn´t you just wire it with cables, special reasons that you made a board ?
What type of C64 have you put the ERPOM-PLA in ? (C64C, or an C64) |
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lemming
Registered: Oct 2009
Posts: 44 |
Whoa, I didn't expect an examination there :D I really don't have an idea how many days I've been using it.
I made a board because it was fast to do. It's currently in one of my dozen Assy250425's.(=C64B"2")
I've got plenty of PLA:s but I just wanted to give a shot at building one of these 'coz it seemed interesting.
Now, I think you should stop fussing and give it a shot too ;-) if it somehow doesn't work for ya, then just appreciate the experience of having some fun with hardware 'modding' and then go eBay-hunting for an original PLA or something :).
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Digger
Registered: Mar 2005
Posts: 437 |
You can also try this one as well. I got one, it's cheap and works out of the box :)
http://www.manosoft.it/?p=14&lang=en |
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8bitforever
Account closed
Registered: Oct 2009
Posts: 48 |
Lemming, thanks for the information.
Digger, how long have you been testing it now ? (how many days)
Digger, have you noticed any bugs ? (manosoft says that the compatibility is 99%)
Digger, what type of C64 have you put the ERPOM-PLA in ? (C64C, or an C64) |
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Sabbi
Registered: Jan 2002
Posts: 8 |
I could not resist to upload a small Video to YouTube:
http://www.youtube.com/watch?v=OHevwgKo9YI
This shows my C64 with an Eprom-PLA (M27C512-15XFI) - notice the interesting color-effects.
The same Eprom works fine in another C64 (same Assy 250407), so it's a bit random what you get..
For a serious (demo-)machine, try to get an original PLA. |
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