Hi- I'm new to the group after meeting Evan at Infoage recently. My 12 year old son is a vintage computer/vintage video game fan. We picked up a non-working Commodore 64 as our first project. We watched a few YouTube videos and ran the suggested basic diagnostics and found that the power supply produces the correct voltages, the fuse is good, and there is the correct voltage at several key locations on the board. Connecting the RF modulator to a TV doesn't change the picture (still only snow) and connecting via the 8 pin jack to a Commodore monitor produces nothing. The computer is an cosmetically good shape and does not appear to have ever been opened up as the RF shield was intact. I note that only three of the large chips are on sockets. Any suggestions for next steps? Thx, Mike
Hi Mike, welcome to the group. I am one of the "Commodore guys". Congratulations on your entry into the wonderful world of Commodore! Look out for Evan's trash talk, he is an Apple guy. ;-) Your diagnostics sound good so far, but hard to go further via e-mail. Where do you live, are you near the museum? I am in PA but might be able to meet you there and work on it with you sometime. Let me know what you think. Chris On Sep 18, 2018, at 1:25 PM, Michael Pohl via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote: Hi- I'm new to the group after meeting Evan at Infoage recently. My 12 year old son is a vintage computer/vintage video game fan. We picked up a non-working Commodore 64 as our first project. We watched a few YouTube videos and ran the suggested basic diagnostics and found that the power supply produces the correct voltages, the fuse is good, and there is the correct voltage at several key locations on the board. Connecting the RF modulator to a TV doesn't change the picture (still only snow) and connecting via the 8 pin jack to a Commodore monitor produces nothing. The computer is an cosmetically good shape and does not appear to have ever been opened up as the RF shield was intact. I note that only three of the large chips are on sockets. Any suggestions for next steps? Thx, Mike
Welcome Michael.
Any suggestions for next steps?
Assuming you've checked all the voltages across the entire board..... After voltages I start looking at clocks, and some basic chip signaling. Feel the chips for thermal issues is usually a good idea too. If the CPU is largely idle (check the CPU A0 or D0 pin) take a look at the reset pin on the CPU and trace that back. If I remember correctly (its been a while), you'll see a timer chip that is responsible for bringing the CPU out of reset and dealing with the out-of-reset on sequence after a minimum amount of time after power is applied. You'll want a scope for this, although you can broadly get away with a meter for basic work. Sounds to me like maybe the CPU is being held in reset. -- Steven Toth - Kernel Labs http://www.kernellabs.com
Hello Michael, There are a number of issues that could be wrong. The best thing is to bring it to one of our repair workshops. I will be scheduling them soon. There will be one in January, February, and March. If you are local to InfoAge, then I would be able to help you out earlier than those dates. Jeff Brace On Tue, Sep 18, 2018 at 1:36 PM Michael Pohl via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Hi-
I'm new to the group after meeting Evan at Infoage recently.
My 12 year old son is a vintage computer/vintage video game fan. We picked up a non-working Commodore 64 as our first project. We watched a few YouTube videos and ran the suggested basic diagnostics and found that the power supply produces the correct voltages, the fuse is good, and there is the correct voltage at several key locations on the board. Connecting the RF modulator to a TV doesn't change the picture (still only snow) and connecting via the 8 pin jack to a Commodore monitor produces nothing. The computer is an cosmetically good shape and does not appear to have ever been opened up as the RF shield was intact. I note that only three of the large chips are on sockets. Any suggestions for next steps?
Thx,
Mike
-- ========================================= Jeff Brace Vice President Vintage Computer Federation
participants (5)
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chrisjpf33＠gmail.com -
Evan Koblentz -
Jeffrey Brace -
Michael Pohl -
Steven Toth