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Commodor 64 green line

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GravityCrab

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Ok so I just picked up a C64 and the only thing I can get out of it is this green line on the screen. Anyone have a clue where I should start?
 

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What type of connection are you using? 5 or 8 pin video cable. What manufacture of TV. Most newer TV's will not display a correct picture without using a 8 pin din to s-video cable.
 
An F connector to RCA adapter isn't going to do anything unless the RCA connector is plugging into an RF modulator that's inside the Commodore 64.

Signals carried inside television coax are very different from signals carried by composite video.
 
I've found quite a few modern TVs like that which do precisely what I see there (even when they are upright) when plugging in older electronics.

I would double check with a different monitor before condemning the C64.
 
Stone said:
So a CRT TV or composite monitor would probably do the trick?
Click to expand...

Certainly.

I did see a demo of an LCD that has hardware to emulate the real, analogue characteristics of CRT support circuitry. It looked impressive in the demo, and may just work.
 
KC9UDX said:
I've found quite a few modern TVs like that which do precisely what I see there (even when they are upright) when plugging in older electronics.

I would double check with a different monitor before condemning the C64.
Click to expand...

I just tried it on my big Panasonic crt tv. Same thing. The only thing that I haven't changed is how the c64 is connected to the tv. I've got it hooked with a coaxial to rca. Which works in my other (also shot) c64s. :confused:
 
GravityCrab said:
I just tried it on my big Panasonic crt tv. Same thing. The only thing that I haven't changed is how the c64 is connected to the tv. I've got it hooked with a coaxial to rca. Which works in my other (also shot) c64s. :confused:
Click to expand...

Ya I thought so. Coaxial connection to rca hes referring to is actually the rca jack style rf connector on the c64, not composite video. One easy test you can do is to get a length of wire for the luma signal out on the 6567R8 chip, pin 15 and plug that into the rca yellow of your crt. You should gat a fuzzy black and white image of what you are supposed to be seeing. The fact that you have any video at all indicates that the PLA(906114-01) 6510, 6581, and 6526s are working, which ive had even non essential chips lkke sound and uart cause black screen due to shorts. Youre screen isnt blank indicating the timing is working, and its not shorted. I suspect that the 6567R8, or the rf modulator are malfunctioning. If you can rule out the 6567R8, and you are left with the rf modulator...which given the symptoms i think is the most likely. If it is, replace the electrolytic capacitors inside the rf modulator's shielding box.

Edit: after posting i thought about it for 5 minutes and realized that obviously its not the rf modulator, because you plugged it into a crt and werent getting snow. Its the vic chip. YOu can get a replacement here:

Http://www.oldsoftware.com

Another thing to check is if it is a PAL machine, or NTSC. This will be labelled on the stencil layer near the 74xx vco and the timing crystal, as well as near the rf modulator. I know the ntsc crystal is 14. Blah blah mhz. The PAL video will be a different chip # and different crystal...i forget what they are.

Hope that helps. Also if you get 80 column programs, running the luma signal only via coax to luma rca( not rf) will enhance the image quality and help it be more clear. So it may be worth the time to wire up a decent luma only switch and cable for black and white 80 column. Kinda like a poor mans 128...without all the button pressing at boot up.

I also thought of this! If im right and its just the video...try doing commands to IO like loading tape, or poking values from the manual to creat SID sounds to prove the system is working.
 
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