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 Post subject: Sega Genesis: Weird Black and White Video issue
PostPosted: Tue Jun 05, 2012 12:42 pm 


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Location: Waterloo, On, Canada
Ok guys, I'm really stumped by this one and I'd greatly appreciate any thoughts you might have as to what the root problem is. Long and short, no matter what combination of Sega Genesis or input, my 36" Sony Trinitron always displays black and white video. Other consoles on the same inputs are in proper colour, as is the Genesis if I hook it up to any of my other Trinitrons. This makes no sense to me. Here's the combinations I've tested.

Hardware:
36" Sony Wega FD Trinitron KV-36FV27
36" Sony Trinitron (one generation older)
34" Sony Wega FD Trinitron 34XBR800
34" Sony Wega FD Trinitron 34XBR960
Genesis Model 1
Genesis Model 2

Test 1:
KV-36FV27
Genesis Model 1
RF Connection

Result: B&W

Test 2:
KV-36FV27
Genesis Model 2
RF Connection

Result: B&W

Test 3:
KV-36FV27
Genesis Model 1
Composite Connection (Front and Rear Inputs tested)

Result: B&W

Test 4:
KV-36FV27
Genesis Model 2
Composite Connection (Front and Rear Inputs tested)

Result: B&W

Test 5:
KV-36FV27
NES
RF connection

Result: Colour

Test 6:
KV-36FV27
AV Famicom
Composite Connection (Front and Rear Inputs tested)

Result: Colour

Test 7:
Other 36" Trinitron, 34XBR800, 34XBR960
Genesis Model 1 and 2
RF and Composite

Results: Colour (No combination was B&W)

The only consistent B&W failure is the KV-36FV27, but even then it's not consistent video inputs. I'm really stumped on what's happening here. Any ideas?
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Tue Jun 05, 2012 3:57 pm 



Joined: 19 Mar 2010
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Location: UK
Sounds like a region "issue" (50/60hz) with the TV (and probably input setting), console and / or game being used.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Tue Jun 05, 2012 5:10 pm 


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fagin wrote:
Sounds like a region "issue" (50/60hz) with the TV (and probably input setting), console and / or game being used.


I agree that's what it sounds like, but all TVs and all consoles being used are 60hz NTSC. As are the games.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Tue Jun 05, 2012 6:03 pm 


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Strange... I had a 20" tube TV of from the 80s that had the same issue with composite video from a SNES. My KV-32XBR100 never had any issues displaying composite video from my Genesis 2, nor does my PVM-2030. One solution would be to get a SCART RGB cable and a SCART RGB to Component converter. This way you'd get better picture quality and solve the chroma decoding (or encoding) issue you're encountering.

http://www.shopncsx.com/rgbscartcable.aspx

http://www.ebay.com/itm/SEGA-SCART-to-R ... 3362ac07c8


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Tue Jun 05, 2012 6:58 pm 


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My concern is figuring out why this is happening in the first place. I can just hook it up to another TV if I want, but I'm just deeply confused by the root issue. I mean we're talking multiple consoles and connections here.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Wed Jun 06, 2012 3:14 am 



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The only thing I can think of is that Genesis is somehow weird about generating the NTSC colorburst (wrong timing relative to hsync, off-spec frequency, weird waveform generating unfiltered harmonics, etc.) in a way that most sets tolerate but that happens to confuse the decoder on that particular model. A lot of consoles play a bit fast and loose with NTSC/PAL signaling standards. Genesis does use a real encoder (Sony CXA1145 I think) as opposed to NES-style shenanigans, but those often depend on a tight clock and external RC networks to make everything correct.


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Wed Jun 06, 2012 8:55 am 


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^ This, My Mk1 Genesis is one of only two consoles (the other being Amiga @ 60hz) that won't Vsync lock on my setup because the timings are just that little bit out of spec.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Thu Jun 07, 2012 8:39 pm 


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Cool. That sounds like a pretty valid explanation to me. Thanks guys.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jun 15, 2012 7:41 am 


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Having the exact same problem with my "new" sony trinitron tube tv.

What worked for me was to use an AV switch selector. While the genesis is on, if I switch to another system that is displaying in colour then switch back to the genesis everything displays normally. Pain in the ass but cheapest solution I found.


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jun 15, 2012 7:49 am 



Joined: 29 Apr 2012
Posts: 1090
I have a similar issue, though it's not a problem. My Model 1 Genny seems to have lost the ability to output an RF signal, all I can get is a very dim picture in flickering red/blue. Tested on multiple CRTs and the same thing happened. Thankfully I can output to composite via a 32X, and it looks better.


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jun 15, 2012 1:55 pm 


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Mark III wrote:
Having the exact same problem with my "new" sony trinitron tube tv.

What worked for me was to use an AV switch selector. While the genesis is on, if I switch to another system that is displaying in colour then switch back to the genesis everything displays normally. Pain in the ass but cheapest solution I found.


Interesting. I'll have to give that a try. What Model Trini?
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jun 15, 2012 9:59 pm 


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36", no idea what model, was a freebie.
Looks like my Japanese PS2 also only likes to display in black and white while my US one works just fine. My switching trick isn't working either. This TV is a piece of crap, I'm moving my old one back. Damnit, I don't want to move the sony again, that thing is huge and has the mass of a dying sun.


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Sat Jun 16, 2012 11:41 pm 


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Location: Waterloo, On, Canada
So update on this:

I tried switching between feeds with a switch box as recommended and sure enough I was able to get colour video from the Genesis, though it was rather dull. Oddly, I discovered that the console does always show in colour if I am looking at the Genesis input in the PIP window and it's more vibrant. Curiouser and curiouser.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jul 13, 2012 2:51 pm 


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Interestingly I've now noticed that this problem is also occurring with my Sega Master System. Looks like this was a problem until the Saturn era.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jul 13, 2012 4:15 pm 


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What kind of MD do you have btw? I discovered that although my Genesis was in a Genesis case, it was actually a PAL motherboard someone had converted. Have you opened yours up to have a look? Could it be an Asian Megadrive that's been half-converted back to NTSC?
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jul 13, 2012 7:53 pm 


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BuckoA51 wrote:
What kind of MD do you have btw? I discovered that although my Genesis was in a Genesis case, it was actually a PAL motherboard someone had converted. Have you opened yours up to have a look? Could it be an Asian Megadrive that's been half-converted back to NTSC?


I am certain that all my Genesis consoles are legitimate. I've had all of them apart for cleaning and I actually know the history of some of them from original purchase to my ownership. Plus the the NA Master System I have was purchased brand new in London, Ontario, Canada by a friend of mine in the 80s and was in his possession until I acquired it from him ~2 years ago.

Switching between a working NTSC source and back to the Genesis or SMS does produce a colour signal, though it's still a touch dull. As this only happens on one of my four Trinitrons and with all my pre-Saturn Sega systems, I'm inclined to believe that it is indeed a signal timing tolerance issue as Ex-Cyber suggested. I wish I had the test equipment on hand to actually verify this.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Sun Jul 15, 2012 4:31 am 



Joined: 27 Apr 2010
Posts: 40
Do the simple, 2 transistor/2 resistor S-Video mod to the Genesis and use a pot on the Chroma line instead of a resistor. Adjust the pot for the color to show.

RJ


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Wed Jul 18, 2012 1:51 am 



Joined: 25 Oct 2007
Posts: 1403
channelmaniac wrote:
Do the simple, 2 transistor/2 resistor S-Video mod to the Genesis and use a pot on the Chroma line instead of a resistor. Adjust the pot for the color to show.

RJ
Wait a tick. Does this somehow tweak the group delay of the filter enough to put the colorburst on a different line? What the fuck. I really need to review my Circuits & Systems textbook.


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Wed Jul 18, 2012 3:07 pm 



Joined: 27 Apr 2010
Posts: 40
Ex-Cyber wrote:
channelmaniac wrote:
Do the simple, 2 transistor/2 resistor S-Video mod to the Genesis and use a pot on the Chroma line instead of a resistor. Adjust the pot for the color to show.

RJ
Wait a tick. Does this somehow tweak the group delay of the filter enough to put the colorburst on a different line? What the fuck. I really need to review my Circuits & Systems textbook.



Doesn't delay it... Some TVs are very touchy with the levels output by different systems. This mod simply lets you turn things up or down which can help with some TVs. My 32" Sony Bravia HD Monitor is very touchy for chroma levels and will disply things in B&W where my little 15" Philips LCD TV shows color. By using a pot with the mod, instead of a fixed resistor, I could adjust the chroma level and get the Sony to display color.

RJ


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Thu Jul 19, 2012 2:20 pm 


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I mentioned this to Ex-Cyber, but I should probably post it here as well. I did a little research and found that the Genesis outputs the NTSC colorburst at 228 lines, not the spec value of 227.5. As far as I'm concerned this seals his theory that it's just outside of the tolerance of my TV. Half a line may not seem like a lot, but if can make a huge difference. What's also interesting is that this should mean that the video circuits for the PIP display have a different tolerance than the ones used for the main display.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jul 20, 2012 5:26 am 



Joined: 25 Oct 2007
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Wait, isn't the color burst transmitted on every line? It's been ages since I've actually looked at an NTSC waveform.

I could see chroma levels being an issue, particularly with newer sets using higher-integration and lower-voltage designs (less margin between spec and amplifier rails)


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jul 20, 2012 4:20 pm 


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Ex-Cyber wrote:
Wait, isn't the color burst transmitted on every line? It's been ages since I've actually looked at an NTSC waveform.

I could see chroma levels being an issue, particularly with newer sets using higher-integration and lower-voltage designs (less margin between spec and amplifier rails)


Yeah I remembered that wrong. It's 227.5 cycles of colourburst per line, for a frequency of close to 3.6MHz. Genesis is 228 cycles per line.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Sat Jul 21, 2012 12:53 am 



Joined: 27 Apr 2010
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3.579545MHz ;)

That's as far as I remember it, but it does continue on.


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Sat Jul 21, 2012 2:06 am 



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channelmaniac wrote:
3.579545MHz ;)

That's as far as I remember it, but it does continue on.
That's as far as I remember it too. AFAIK, typical crystal oscillators don't even get you that many digits (50 ppm being a typical stability rating). ;)


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Sun Sep 02, 2012 4:11 pm 


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I also have a Sony Trinitron Wega ( 32XBR250) and it has the same B&W issue with my genesis model 1. It also happens with my Colecovision. It is seriously annoying. I wanted to buy a second Trinitron but im not sure anymore because of this. I also have a 32" LG flatron that has no B&W issue but i think the Trinitron has a better overall picture.


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Tue Sep 04, 2012 3:14 am 


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Just get a switch box and switch to w working colour signal and then back to the BW one. It will sync the colour. That's what I've been doing since I uncovered this.
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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Thu Jul 12, 2018 3:55 am 



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The funny thing is I go through my VCR into the Sony Wega, my colecovision is in B/W, then I play a color VHS tape, and the color appears. Then I stop the tape, it's B/W. I also tried switching inputs, but that doesn't work. Do I have to switch channels? If so there is nothing but video games on channels these days with NTSC being obsolete.

By the way, I heard these have even better pictures than a Sony Wega, just want to know if it's worth changing TVs for a color Colecovision.

The TV is a Daewoo 20 inch Flat Screen Composite/S_Video/Component 480i CRT TV. Good TV to kick the Sony to the curb just for this Colecovision problem? i got one handy, I just need help moving it.


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 Post subject: Re: Sega Genesis: Weird Black and White Video issue
PostPosted: Fri Jul 13, 2018 2:10 am 



Joined: 24 Apr 2016
Posts: 5
tripletopper wrote:
The funny thing is I go through my VCR into the Sony Wega, my colecovision is in B/W, then I play a color VHS tape, and the color appears. Then I stop the tape, it's B/W. I also tried switching inputs, but that doesn't work. Do I have to switch channels? If so there is nothing but video games on channels these days with NTSC being obsolete.

By the way, I heard these have even better pictures than a Sony Wega, just want to know if it's worth changing TVs for a color Colecovision.

The TV is a Daewoo 20 inch Flat Screen Composite/S_Video/Component 480i CRT TV. Good TV to kick the Sony to the curb just for this Colecovision problem? i got one handy, I just need help moving it.


Just as I say that yesterday, I decided to TRY my Daewoo. Don't kick the Wega to the curb, becuaase the Daewoo was also in black and white. Also at times they both were monochrome with rainbow banding and snowy color.

I guess it's a problem with my Colecovision.

I opened by Colecoviiosn and see a pinhole where something can eb turned i the Silverf RF Box. I heard that's how you adjust the SNES. MAybe something similar can be doen with a Colecovision.

Also would a Composite, S-Video or Component mod do it? I'm not handy at all with a soldering gun, so I'll have to hire someone to do it. Any suggesitons? Am will that end my B/W RF problems once and for all?


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