Sunday, April 10, 2016

C64 G - Black screen :(

I got my hands on a C64 G, a nice and beautiful one. Warranty seal was untouched so I had high hopes when I turned it on... then nothing happened.


Ok, that's bad.
I quickly plugged in another PSU and voila, the machine was... almost alive.
Black screen, nothing else.


That means, I had to remove the warranty seal and check what's going on inside the C64.
The memory chips were heating up very quickly, so it seemed obvious they were defective.


Others were fine, no presence of overheating so I thought the solution will be simple.
I started to search for replacement chips and sockets immediately.


Ordered a pack of sockets (sidenote: it's much cheaper if you order 20+ pieces than order only 2...) and finally found XX464 memory chips as well for a good price. So, I removed the defective chips and soldered the sockets.


And...
After memory replacement it still doesn't work :(
Black screen.
So I have to dig deeper and find out what might be the problem.


I even tried to touch the G-spot but didn't help :(
 

.....



Today's music: X Marks The Spot - 64k Intro by Portal Process
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4 comments:

  1. PJMirandaApril 29, 2016 at 12:00 AM

    Hi,

    Did you already found the problem who is causing the black screen?
    I have two boards PCB 250469 with the same problem.
    Continue with good work in your blog! ;)
    Regards

    ReplyDelete
    Replies
    1. StrayBoomApril 29, 2016 at 9:55 AM

      Hey, sadly, I had no time to go through of all possible defects yet and I would need some spare parts as well.

      In your case, I would start with checking the chips on the board, try to find the extremely overheated ones, those will be broken - like the memory chips on my board. If replacing the overheated chips doesn't help, well, the next step would be to use oscilloscope and other equipment to check the circuit and various parts. But that's a tricky task and maybe it would be better to ask an expert about it.

      I will post more about my C64 G once I find the time - and the broken part - to fix and write about it.

      Delete
    2. PJMirandaApril 30, 2016 at 11:38 PM

      I will folow your tips .
      When you have news of C64G sharing.
      Thanks! ;)

      Delete
  2. Steve DayFebruary 20, 2017 at 7:20 AM

    I have a 250469 board with the same problem. I haven't had a chance to dive into it yet with the soldering iron, but from reading different diagnostic tips (Ray Carlsen etc) I have a hunch it's the 7406 (SN74LS06N is fine as a lower power replacement). I have an almost complete set of Omron ultra-low profile sockets for the board (XR2A series) - though can't find the 64pin socket for the SuperPLA (hopefully it's not that anyway).

    Good luck with yours.

    ReplyDelete

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