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Device or circuit to emulate green/amber monitor on a color monitor?

T

telengard

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Joined
Nov 27, 2004
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Location
Hudson, NH
Just wondering if such a device/box/circuit exists (or is even possible). One of my previous monitors had a mono switch which went from color to green. I imagine it just routes the R and B output to the green gun since the signals have already been decomposed. I really don't want to modify my 1702 (and to be honest wouldn't be exactly sure what to do).

Ideally such a device would allow for composite or chroma input and have a pot or dial to choose the end result color and then just be plugged into a monitor.
 
It would be very easy to modify the monitor to do that, but, at least in my opinion, monochrome on a color monitor is very hard on the eyes, exactly the opposite of monochrome on a monochrome monitor.
 
I think it'd be doable like your theory but I'm not sure where the best point would be for that sort of hack. A dumb but simple solution would be to put a green screen transparency over your monitor. It was good enough for Vectrex. ;-)
 
.
KC9UDX is right.
I'm bold when it comes to trying this stuff.
I would get a CGA extension cable (or 9-pin Male to Female cable that fits) and modify/experiment on the extension cable.
See the attached picture for reference.. I would simply disconnect the R and B pins and see what happens.

http://www.moncotech.com/products/mvc007/spec.php
mvc007-9pin.jpg
 
You know, you can do black & white monochrome on a 1702 without any modifications. Just plug a composite video source into the LUMA plug and leave the CHROMA one open.
 
Love the vectrex idea. :)

As for the luma, I could do that I was really hoping for green or amber. I played a lot of games as a kid on a green only monitor and was just thinking maybe that would be possible.
The luma w/ a green transparency might be do-able though.

If I *were* to modify my 1702, is it just as simple as using a switch to route the R and B outputs to the green gun or does it have to go through some kind of small circuit?
 
If you were going to play like that I'd go with luvits idea and just modify a cable so you can play around. Either combining them all to G would probably work or just not using the R and B may also be fine.
 
I think we're talking about a Commodore 1702, which doesn't have a CGA connector, and is "S-Video", with no distinct R,G,B inputs. But, I could be wrong.

I don't have a schematic for a 1702 handy. What you basically want to do is put the individual electron guns for red and blue into cutoff. That means making their control grid potential significantly more negative than the cathode(s). There are many ways to do this, and which route to take depends on the design of the monitor. There may be intensity adjustments for each color on the board at the back of the CRT. If that's the case, you can use DPDT switches to "adjust" the potentiometers all the way "down" by switching the switches.

Be careful, 2nd anode potential can kill you. Or, at least make you wish you never took your monitor apart. You won't likely be encountering that working on this type of project. However, I don't like modifying anything in a CRT monitor without first discharging the 2nd anode with a high voltage probe. Just be aware of what you are doing and it would be a fun project.

I'm trying to think what monitor it is that came with a switch to turn everything green. It must have been the 1802. Whatever it was, I had one.
 
telengard said:
Just wondering if such a device/box/circuit exists (or is even possible). One of my previous monitors had a mono switch which went from color to green. I imagine it just routes the R and B output to the green gun since the signals have already been decomposed. I really don't want to modify my 1702 (and to be honest wouldn't be exactly sure what to do).

Ideally such a device would allow for composite or chroma input and have a pot or dial to choose the end result color and then just be plugged into a monitor.
Click to expand...
How about a nice green Sony composite monitor instead? Even has built-in audio...

Long persistence though, kinda like an IBM mono monitor; what are you connecting to?
 
KC9UDX said:
I think we're talking about a Commodore 1702, which doesn't have a CGA connector, and is "S-Video", with no distinct R,G,B inputs. But, I could be wrong.

I don't have a schematic for a 1702 handy. What you basically want to do is put the individual electron guns for red and blue into cutoff. That means making their control grid potential significantly more negative than the cathode(s). There are many ways to do this, and which route to take depends on the design of the monitor. There may be intensity adjustments for each color on the board at the back of the CRT. If that's the case, you can use DPDT switches to "adjust" the potentiometers all the way "down" by switching the switches.

Be careful, 2nd anode potential can kill you. Or, at least make you wish you never took your monitor apart. You won't likely be encountering that working on this type of project. However, I don't like modifying anything in a CRT monitor without first discharging the 2nd anode with a high voltage probe. Just be aware of what you are doing and it would be a fun project.

I'm trying to think what monitor it is that came with a switch to turn everything green. It must have been the 1802. Whatever it was, I had one.
Click to expand...

Exactly, the input is composite or s-video, not RGB. And, yep, I could modify the 1702, but I'd rather not, but I will if that's what it comes down to. :)

I was thinking that if there was some device that could work with any monitor that would be more ideal. Modify the composite (or chroma) signal before it goes into the monitor. That is probably making it more difficult than it needs to be, but I was just curious. I'm also looking for a project, and this sounds like fun. Just didn't want to reinvent the wheel, or attempt something that is way beyond my skills.

@MikeS I do have a small Zenith green monitor, but I don't have a lot of space and the 1702 gets a lot more use, but occasionally I'd like the green or amber.
 
What if we can figure out which monitor it is that can switch to monochrome? Would you be open to switching out the 1702 for that? It may be the most economical solution. There wouldn't be a project though. :(

I did a quick image search, and this sort of confirms it was an 1802:
1802.jpg

I wish I still had mine, I'd gladly trade you.:D
 
Hehe, I have an 1084 equivalent (Magnavox RGB, which does take composite) and it has the green switch on it, but I just love my 1702. I use the Magnavox for the ST, Amiga, and IIgs. I wonder if the 1802 supports the s-video of the C64? I'm pretty vested in the Magnavox having made cables for the computers to work with it (and also have a spare monitor of the same kind in case it breaks). I'll have to look into that.

And yup, part of this is looking for a project, although keeping all these computers in working order is a project in itself! Seems I get about 2 hours of use for every 1 hour of fixing lately.

Also, I'm partial to the Amber look too, which my Magnavox can't do. :)

Thanks everyone for the suggestions so far, learning a lot!
 
KC9UDX said:
I think we're talking about a Commodore 1702, which doesn't have a CGA connector, and is "S-Video", with no distinct R,G,B inputs. But, I could be wrong.

I don't have a schematic for a 1702 handy. What you basically want to do is put the individual electron guns for red and blue into cutoff. That means making their control grid potential significantly more negative than the cathode(s). There are many ways to do this, and which route to take depends on the design of the monitor. There may be intensity adjustments for each color on the board at the back of the CRT. If that's the case, you can use DPDT switches to "adjust" the potentiometers all the way "down" by switching the switches.

Be careful, 2nd anode potential can kill you. Or, at least make you wish you never took your monitor apart. You won't likely be encountering that working on this type of project. However, I don't like modifying anything in a CRT monitor without first discharging the 2nd anode with a high voltage probe. Just be aware of what you are doing and it would be a fun project.

I'm trying to think what monitor it is that came with a switch to turn everything green. It must have been the 1802. Whatever it was, I had one.
Click to expand...

Yup, always careful, I made a little high wattage resistor thing to drain caps, haven't tried it on a monitor, but it should work fine. Should beat my old method of a screwdriver. :p
 
I once made a discharging "chicken stick", I think about 5M ohm for discharging CRT 2nd anodes. I got zapped more times trying to connect that thing than I ever did trying to discharge CRTs any other way. Eventually I bought a high voltage DC voltmeter probe, and I now use that. I've never had a problem with that, and, it gives an indication of the voltage which is great.

And, yes, the 1802 supports the "s-video" method of connecting to a C64. I think it was designed for the C128. I used my 1802 with a C64C back when the monitor was brand new.
 
KC9UDX said:
I once made a discharging "chicken stick", I think about 5M ohm for discharging CRT 2nd anodes. I got zapped more times trying to connect that thing than I ever did trying to discharge CRTs any other way. Eventually I bought a high voltage DC voltmeter probe, and I now use that. I've never had a problem with that, and, it gives an indication of the voltage which is great.

And, yes, the 1802 supports the "s-video" method of connecting to a C64. I think it was designed for the C128. I used my 1802 with a C64C back when the monitor was brand new.
Click to expand...

I knew I had a different Commodore branded monitor and looked at my list of stuff in storage, and it is an 1802. Maybe I should switch that in for the 1702. That would give me everything I'm looking for, sans a fun project (and amber <sob>). :)

I really do like how the 1702 looks though, and it is a workhorse. Only thing that continues to work for me!
 
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