LCD TVs and VIC 20s

Post by **Jeff-20** » Sun Mar 13, 2005 8:08 pm

Why won't my vic 20 work with an LCD Monitor?

I have a "TFT LCD TV" from Hong Kong. When I run a vic thru a vcr to the monitor (because it has no RF), I get an ghostly "off picture" as if it is set to the wrong channel. When I run the same line from the VCR to ta regular CRT TV, I get a good picture. Why is this so?

Is the signal too weak? I hooked a TurboGrafx 16 to the vcr and it worked well. What's up?

Tepic · Post by **Tepic** » Mon Mar 14, 2005 4:16 am

Wild stab in the dark this, from my old days as a TV salesman!

It could be that the Vic and VCR are using the on the same channel.

Try adjusting the channel your VCR uses either in software or by turning a tiny screw on the back. That might fix it.

Post by **Jeff-20** » Tue Mar 15, 2005 3:39 am

I think I solved it.

The signal in older machines seems weak. I had the same problem with my original Atari 2600. IT wouldn't work with the A/B switch, but it was fine with a direct connection to the TV.

The Vic 20 seems to have the same problem. A weak signal or something. It works better with less devices between the computer and the television.

I wonder if there is any simple way to boost the strength of the signal.

carlsson · Post by **carlsson** » Tue Mar 15, 2005 5:12 am

On the non-CR model, there is both video high and video low, of which the latter has 50 ohm resistance? I never found out the difference, but maybe one will give a stronger video signal?

MagerValp in comp.sys.cbm mentioned something about interlace and LCD TV, that some televisions don't display the interlaced screen properly. Since you live in NTSC land, you may try POKE 36864,PEEK(36864)OR128 to toggle the interlace mode of the 6560 chip and see if the output gets better?

Anyway, why would you go through RF if the computer has composite output and the TV in some way can input such signal?

Boray · Post by **Boray** » Tue Mar 15, 2005 5:35 am

carlsson wrote:On the non-CR model, there is both video high and video low, of which the latter has 50 ohm resistance? I never found out the difference, but maybe one will give a stronger video signal?

I was about to say the same thing... So, are you using the video-low pin, Jeff? (A C64 video cable)

/Anders

Post by **Jeff-20** » Wed Mar 16, 2005 1:04 am

I didn't know there was any other option.

The vic has a single RCA style plug (forgive my ignorance of video terminology). I plug it into the VCR because the LCD TV only has a A/V (2 seperate lines) type input. It is a mini LCD with male cables coming out of the bottom (and into my vcr...

)

What should I have done?

Boray · Post by **Boray** » Wed Mar 16, 2005 1:37 am

Is the vic20 the 2-prong power plug model?

Does the video cable you use also work with a C64?

If yes, then the "video low" pin of your vic's video port is used instead of the "video high" pin. On my "non-CR" Vic20, the video low pin generates a really weak ghost picture while the high pin gives a strong picture that looks as it should.

/Anders

carlsson · Post by **carlsson** » Wed Mar 16, 2005 4:35 am

Jeff-20 wrote:The vic has a single RCA style plug

Is this the cable that comes from the RF modulator, or directly from the VIC? The output typically is composite video (one RCA plug) and mono audio (one RCA plug), or if fed through RF, one coax plug.

What me and Boray are trying to say is that if you had a composite video cable that connects directly between the VIC and the TV/monitor, you could try to use (modify it) a different pin on the video out connector to get a stronger signal. I'm not sure which of the two signals the RF modulator will work with, but I suppose the weaker.

Post by **Jeff-20** » Wed Mar 16, 2005 11:15 am

ah... I think I understand now. I don't have a C64, but I have both types of VIC (power supply variations). I also have an AV cable as you described (for the 64). I got it from a thrift store and never tested it on a VIC. It has been sitting in a box of junk for years. I guess it is time for experiments.