Hello Everyone!

mr zetec · Post by **mr zetec** » Thu Sep 03, 2009 1:52 pm

I need help with two vics. The first is simple it works totally fine except the paddles dont read right: I think this is a problem on the board due to a failing capacitor. It is the old 2 pin bigger board. WHERE IS THE TIMING CAPACITOR FOR THE PADDLE on the motherboard? I need to know so I can renew it!
Secondly, my newer small motherboard VIC has a different problem. It works fine except there is a gap between horizontal pixels, so for example if I type "_" it looks more like "...."
Please help
Oh, and Hello to SHEM, I thought you were just into Commodore16s!

shem · Post by **shem** » Thu Sep 03, 2009 2:29 pm

Hi Mr zetec
i am into most commodore 8 bit machines
both machines are fixable
there is no timing capacitor for the paddles your paddles are connected to capacitor c13 and c14 and also to the vic 6561 chip it is more likely that the a/d converters are shot on your vic6561 chip

the 2nd newer vic sounds like it has a rom problem or if you're unlucky it could also be the vic 6561 chip

you could try to swap the vic 6561 chips remove the vic chip form your newer vic and fit it into the older machine that should get your older machine going as for the newer machine if it is a rom problem then you will need to replace the 901460 chip it is marked UD7 on the newer board

hope this helps
if you get stuck give me a shout...

Mike · Post by **Mike** » Thu Sep 03, 2009 2:39 pm

Regards the second VIC: what display are you using? A monitor or a TV set.

On one monitor I know, there's a switch on the back to select combined or separate luma & chroma. Normally, the VIC provides combined luma & chroma (unless you do the S-Video mod). But the other position also "works", producing the gap patterns with *all* colours except white and black.

mr zetec · Post by **mr zetec** » Thu Sep 03, 2009 3:27 pm

Hello Mike and Shem,
The newer vic pixel gap problem does only apply to colours, black and white are ok. I am using a 15inch lcd tv with the vic video port connected to the AV in. The other vic works fine on the same setup.
So how do I fix this?

shem · Post by **shem** » Thu Sep 03, 2009 3:38 pm

Hi again
in the metal can in the middle of the vic board there are some pots you can adjust to improve the video
here is a link to prev page 3rd pic down shows the area

http://sleepingelephant.com/ipw-web/bul ... ght=svideo

shem...

mr zetec · Post by **mr zetec** » Thu Sep 03, 2009 3:58 pm

Thanks Shem, I already tried the pots and they did not improve it. Please take a look at the attachment:

shem · Post by **shem** » Thu Sep 03, 2009 4:01 pm

cant see any attachments
how are the graphics with a cartridge game are they ok or do they also break up?

mr zetec · Post by **mr zetec** » Thu Sep 03, 2009 4:06 pm

Shem, try the attachment; it should work. The video is like this on carts too...

shem · Post by **shem** » Thu Sep 03, 2009 4:14 pm

well from the pic it looks like it isnt a vic problem but the way your tv processes your machines video signal
an A/V cable or scart cable should give you better results...
have you tried another tv?
dont forget vic 20's were released when there was no wide screen 16:9 just the standart 4:3
try the tv in 4:3 mode not wide screen and see if it improves

mr zetec · Post by **mr zetec** » Thu Sep 03, 2009 4:45 pm

Hello again Shem. The tv is not widescreen. I have tried it on scart and it is the same. The other Vic is perfect on the same equipment.

carlsson · Post by **carlsson** » Thu Sep 03, 2009 5:53 pm

I think the answer is that composite video can be just that bad. The image quality seems to vary a lot from VIC-20 to VIC-20, and it is not due to the VIC chip itself, it must be some accompanying components in the video department.

Some people have modified their VIC-20's to output a S-Video signal instead and report they get a very crisp and nice picture. It is possible that you would get a better result if you took on that modification too.

IsaacKuo · Post by **IsaacKuo** » Thu Sep 03, 2009 8:57 pm

You see a "bad" image...I see the perfect output for subpixel graphics rendering. It looks like a botched S-Video mod where the composite output is connected to Luma (chroma is either also the composite output or just the chroma output).

This is perfect for using the subpixel graphics method. Or it would be perfect with an NTSC model...with PAL you would unfortunately have color flickering due to the different way it works.

a4000bear · Post by **a4000bear** » Sat Sep 05, 2009 12:34 am

I concur with the other posters, your video problem is caused by limitations in the composite video signal.

However, in your case, I can see that your TV uses a 'comb filter' to separate luminance from chrominance and thats where your particular problem comes from. Normally, on ordinary video, a comb filter is the superior way to achieve the separation.

But it falls down on computer graphics as a comb filter needs at least two lines of video signal to do its work. Computer graphics often contains detail in only one line. This effect is sometimes called 'hanging dots'.

In your picture, you can see the colour subcarrier in single horizontal lines, such as on text. However, areas that are of solid colour over many lines don't have that problem...like the background.

The solution is to modify the VIC for S-Video, or to use a TV that uses bandpass filters to separate luminance and chrominance.....howver the picture will be blurry with smeared colours.

mr zetec · Post by **mr zetec** » Sat Sep 05, 2009 1:54 am

hello a4000bear, Are you suggesting I convert to s-video or do you think will be blurry? I will do the s-video conversion but I do not want to change my TV as it works fine with 7 other machines!

Leeeeee · Post by **Leeeeee** » Tue Sep 08, 2009 10:15 pm

WHERE IS THE TIMING CAPACITOR FOR THE PADDLE on the motherboard?

The timing capacitors are C13 for the potY input and and C14 for the potX input. These should be 1nF ceramic and are unlikely to fail.

Lee.