Video Diagnostic needed

[Jeff-20]

I've tried two different VICs, a C64... two different power supplies (one being Ray Carlssen's)... two different video inputs. I am still getting a strange interference. Any ideas of what it could be? (images may be turned 90 degrees because of my phone)

[MCes]

it seems like there are two different sources selected at the same time, both of them analogic.
Some TV have the same input in front and rear but they are wired together so they could be in collision.
Try to disconnect any other input wire at TV connectors.

Mmmmm.....
On C64 based pics there are a strange number of border lines.....
Are you sure that the NTSC/PAL option is selected well?

[eslapion]

This display either takes no account or doesn't receive the horizontal sync.

[Jeff-20]

This display either takes no account or doesn't receive the horizontal sync.

Does this sound like a failure of the video cable or a problem with the power supply? I just got a Ray Carlssen PS, but the symptoms persist.

[MCes]

if image is stable the v and h sync are correctly locked, if the problem is the TV it could be a retrace problem (vertical circuit).
Have you tried with a decoder linked via RGB?

[eslapion]

Does this sound like a failure of the video cable or a problem with the power supply?

Neither. It seems like a problem with your monitor/TV set.

I see the C64 image is blue so I don't think it's a PAL/NTSC problem.

You said you tried 2 different VICs and a C64 - is there anything else plugged to the display when you tried ? If so, disconnect it.

Your VIC, do they have the S-Video mod and you used S-Video or did you use normal composite input ?

Do you have another display to try these machines with ? I use an ultra cheap RCA 19" flat panel TV as a backup and it works perfectly, even better, it supports both PAL and NTSC and senses automatically.

Work by elimination:
- TV set ok? (how many others did you try ?)
- Connection ok? (cable? S-Video? Composite? Is another signal attached to the TV and causing problems ?)
- Computer ok? (you tried 3 so I guess this is not the problem)
- Power supply? (Ray Carlsen's PSU are usually perfectly good but do you have another "known good" source? )

Looking carefully at the first 2 images you posted they seem to come from a C64 as I see a dark blue background with a light blue border so the garbage on top looks like another video signal superposing itself on the C64 video signal.

Some TV have the same input in front and rear but they are wired together so they could be in collision.
Try to disconnect any other input wire at TV connectors.

Very likely...

[Jeff-20]

I will follow all of the above steps I can and post new pics soon.

[Jeff-20]

Ok. I know now that something is wrong with the video cable. I bought a 25 foot cable on ebay.

Screenshot 2016-08-18 at 11.png (140.51 KiB) Viewed 1763 times

I've since contacted the seller and am waiting for a reply.

THe following images use two different VICs and a C64 each with a the same Ray Carlssen power supply. I brought out my old LCD flat screen and connected both cables. The old cable seems fine.

The new cable produces no image.

So, I go back to my CRT, a 20 inch Sony Trinitron with front and back inputs. I have all of my consoles connected to it via composite switch boxes. I connected via switch box then via the front composite input.

With the old cable, both inputs produce a strange band of horizontal static that slowly rolls upward on the screen. You'll have to look very closely to see it. Ignore the dark, diagonal bands produced by camera effect.

It's even present when the system is completely off and all power is cut to the other connected consoles (power strip switch turned off but not unplugged).

I've unplugged the other consoles completely from the television, and the effect is almost gone. I can still see a slight static.

Now, the new cable produces some image on a CRT. It produces a stronger distorted effect before even powering on. Again, horizontal bars that slowly scroll. This is front input with and without other consoles connected to the back input.

When powered on, I can see a faint image that also rolls upward.

I've noticed a strange effect when I started to pull out one of the audio lines and it touched the outside edge or the female connector. It produced a closer to "normal" (stable) image but with horizontal placement issues.

Here's the C64 as well.

I've waited a few days for the seller of the video cable to respond. Should I just pull it apart myself? Is it repairable?

And finally, another interesting observation: I have no image issues with any other console. I have 16 others connected via AV switches (every console generation). The image clarity is amazing. I've held on to this TV so long for that reason. Why would only Commodore machines give me problems?

[eslapion]

@Jeff-20
I don't know if there is anything wrong with your 25' cable but I know I would never use anything longer than 6'.

[Jeff-20]

@Jeff-20
I don't know if there is anything wrong with your 25' cable but I know I would never use anything longer than 6'.

It was described to have extra shielding and seemed to work fine when I first connected it.

[ken]

@Jeff-20
I don't know if there is anything wrong with your 25' cable but I know I would never use anything longer than 6'.

I have built and sold about 100 25 foot cables and even use 1 myself with no issues
and no that one jeff got was not from me

[eslapion]

I have built and sold about 100 25 foot cables and even use 1 myself with no issues
and no that one jeff got was not from me

I find it tends to make the image a bit blurry to use longer cables but that's a personal preference.

As soon as a cable is longer, it has more reactive impedance; if the cable is good quality I suppose you couldn't notice on a VIC-20, it is more apparent on a C64.

[Mike]

Jeff, why are you using 3 RCA plugs on the TV set?

Without S-Video mod the VIC-20 only delivers composite video on one RCA, and mono audio output on another RCA. To see what's on the third RCA you'd have to take a multimeter and check continuity - but in any case it's nothing usable for the second audio channel input of the TV set.

The center pin of one of the RCA plugs must be connected with pin 4 of the DIN plug for the composite signal, and *that* RCA plug - regardless of its colour! - has to go into the video input of the TV set (most probably - yellow).

Same with pin 3 of the DIN plug, which takes the sound signal. The corresponding RCA goes into the L audio input (most probably - white).

Don't connect the third RCA. If it happens to be connected to Pin 1 of the DIN plug, that would carry the luma signal on the C64, but +6 V for the supply of the RF-Modulator with the VIC-20. Neither one would you want to connect to the R audio channel of the TV set!

Here's the pinout as seen onto the pins of the DIN plug (mirrored from the socket):

Code: Select all

   DIN  PLUG

1  o       o  3

    o     o
       o
  4         5
       2

Also check, that the shield (accessible at the outside of the RCA and DIN plugs) is properly connected to pin 2 of the DIN plug. This one has to take the reference signal ground for both video and audio.

[eslapion]

Jeff, why are you using 3 RCA plugs on the TV set?

...

Don't connect the third RCA. If it happens to be connected to Pin 1 of the DIN plug, that would carry the luma signal on the C64, but +6 V for the supply of the RF-Modulator with the VIC-20. Neither one would you want to connect to the R audio channel of the TV set!

I should have seen this one! I am so used to my own video cables with both red and white RCA jacks connected to audio out for compatibility with stereo systems/TVs I forgot this so frequently occurring problem.

[ral-clan]

Yes, I too recently discovered that the VIC carries +6V on one of the monitor out pins. I was using a C64 monitor cable with my VIC-20 and had all three RCA connectors plugged into the back of a 1701 monitor (audio-input, chroma and luma). So I guess I was sending six volts to either the Luma or Chroma input on the monitor!

Once I read about how one of the connectors carries +6V I quickly disconnected that thing! Luckily, even though it had been plugged in for years it had done no damage. Maybe the 1701 is a tough beast. I wouldn't risk it again though. I've since put electrical tape over that RCA connector so I don't plug it in mistakenly (or so it doesn't short to something metal when dangling freely).

Even thought the 1701 survived, I wonder if Jeff damaged the video input circuitry on his TV by feeding it +6V. That might explain why it worked the first time he used it but subsequently won't work properly.

Probably not though, since Jeff seems to be saying it still works with other consoles...more likely the 25' cable is acting like some sort of antennae and picking up interference (hence the rolling band of static even when an non-powered console is connected to the cable).

A couple of other thoughts:

You say, Jeff, that your are connecting everything (consoles, Commodores) to a composite switch box, then THAT is going to the TV. You might have a bad/dirty switch box channel. Have you tried a different input on the switch box? Have you tried connecting the Commodores directly to the TV input?

Perhaps your Commodores are outputting a weak video signal? Some TV's can accommodate for that an boost the signal to spec, other cannot. How the the VIC look on other CRT TVs?

Jeff, just another unrelated thought. Since you cannot see colour, why don't you also turn down all the colour signal on your TV? Even though you are happy with the Sony's picture quality, you might get an even (slightly) sharper image. When I turn down the colour on my Commodore 1701 monitor the picture seems very slightly sharper.