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Forum Index : Microcontroller and PC projects : Connect CMM / CMM2 to 1084s Monitor
| Author | Message | ||||
| Vampire05 Regular Member  Joined: 06/12/2020 Location: GermanyPosts: 88 |
Hi Guys, is it possible to connect the original CMM and CMM 2 to the old 1084s CRT Monitor?  The oldschool RGB Port has similar pin naming like the VGA Port. Edited 2021-07-20 03:25 by Vampire05 |
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
Not that I'm aware of. It's a different system. You may be able to find a converter box but I don't think they are too common. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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SimpleSafeName Guru Joined: 28/07/2019 Location: United StatesPosts: 351 |
Huh, how did you end up with a 9-pin job instead of a SCART version of the monitor? I have a 1084S-D2 and it is quite similar to yours. And I have some Extron boxes in the garage that I use on my Sony PVM. They work fine with my Amiga, and they probably should work here as well. Something like the Extron VSC 500 might work. I'll take a look at my setup and see what I've got (it's been too long since I've fooled with them). |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
You probable could use it by using a VGA to composite converter and running the monitor in composite mode. I assume that the monitor comes in NTSC as well as PAL composite standards. I don't think the scan rate for RGB is compatible with any VGA modes but you never know. Jim VK7JH MMedit |
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| Vampire05 Regular Member Joined: 06/12/2020 Location: GermanyPosts: 88 |
Thank you guys, @SimpleSafeName: i bought this Monitor last week for 70 Euro in my Neighborhood for my C64. I thought its a good idea to have an oldschool RGB Interface :-) I do not have such expensive Extron boxes... @TassyJim: But the Monitor only have RGB and S-Video. How can i connect a composite signal? |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
VGA and CVBS are both analogue signals and, providing they are all there (Red, Green, Blue, Hsync, Vsync), you are unlikely to damage anything by connecting them like for like. However, your chances of getting a usable signal are not good. For a start you'll probably be restricted to 640x480 modes (at the maximum) from the CMM as otherwise I doubt if it will be able to synch. That will largely depend on the monitor's capabilities. Additionally the signal levels could be widely different. VGA in general isn't suitable for broadcast / combined video situations. You can get VGA to combined video and VGA to RGB adaptors, but you will still find them very restrictive in what VGA formats they can handle. The picture quality is usually pretty poor too. Your monitor should be fine for any of the original home computers that produce combined video or RGB outputs. Even those that use an RF modulator might be ok if you can tap the video signal off at the modulator input. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Vampire05 Regular Member Joined: 06/12/2020 Location: GermanyPosts: 88 |
Ok i understand. Thank you for the answer Mixtel90  |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5089 |
Hi Vampire05, First of all, the 1084 monitor has RGB input that is more or less compatible with the old SCART RGB standard. It is analog, suitable for a 15.625kHz line rate. It has either composite sync in red, or composite sync on a separate connector. The composite sync has 0V level for both HSYNC and VSYNC combined. VGA is different. It has 31kHz or higher line rate, and has separate HSYNC and VSYNC signals. Depending on the VGA resolution, the HSYNC and VSYNC signals are inverted. Technically it is possible to combine HSYNC and VSYNC with some logic to a composite sync signal, but it is not possible to drop the VGA framerate from 31kHz to 15.6kHz, unless you buy a frame rate converter (b.t.w. these are available from China, I used one to play PC movies on my old CTR TV). If you apply 31kHz to an analog monitor or TV it is possible to destroy the monitor since some (non-multisync) monitor run the high voltage generator at the frequency of the line rate to avoid visible noise in the picture. Doubling the frequency (15.6 -> 31kHz) may destroy the high voltage generator. And... as proven before ...Google is your best friend....  You will destroy the 1084S when you connect it to a VGA signal... Edit: the CMM (CMM1) has an analog video mode (composite video) in black and white. That will work with the 1084. But does not provide color. Edited 2021-07-21 00:59 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Vampire05 Regular Member Joined: 06/12/2020 Location: GermanyPosts: 88 |
@Volhout: first of all, thank you very much for the very detailed answer. Google is not my friend, it is only a search engine. |
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| SimpleSafeName Guru Joined: 28/07/2019 Location: United StatesPosts: 351 |
Oh, that was a nice price for it. :) I was just surprised that it didn't have a SCART interface. As for the prices for Extrons, I don't have that kind of coin either. So I buy the obsolete ones (which do better for our purposes anyways). I can't recall what I have paid for them, but it wasn't much. For example, on the German eBay site, there is this: https://www.ebay.de/itm/324471978798?hash=item4b8c097b2e:g:OygAAOSwbjhgGEgK Or: https://www.ebay.de/itm/274799706870?hash=item3ffb56c2f6:g:ADsAAOSw8s1goVUx Which *may* work for you. 29 Euros for the first, 13 Euros for the second. The key being that they provide you with a buffered VGA (or RGB) signal that should protect your monitor. But I think that this is the one that you want: https://www.ebay.de/itm/174809270698?hash=item28b371c9aa:g:mSAAAOSw7XZgz10K https://www.extron.com/product/in1502 35 Euros. Do your research first though ;> |
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| Vampire05 Regular Member Joined: 06/12/2020 Location: GermanyPosts: 88 |
@SimpleSafeName: Wow, this is fantastic! The price is awesome! Thank you very much for this advice. Now i will watch on ebay for those boxes. @Volhout: This is the reason why (sometimes) talking with people is much better then googling around! i did not know there was such a solution. |
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| Vampire05 Regular Member Joined: 06/12/2020 Location: GermanyPosts: 88 |
Has anyone had any experience with such boards:  will these boards work with all graphics modes of the cmm? |
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jirsoft Guru Joined: 18/09/2020 Location: Czech RepublicPosts: 533 |
I have no experience with this part, but I'm doing some retro computing with C64, C128, Apple IIC... and I'm usually trying to solve to opposite way (S-video/Composite -> VGA/HDMI) and my 2 cents are: 1. with buffered convertor you can (and probably will) have some sync problems with fast animation coming from CMM2 - it will be synced on VGA side and not on the 15kHz side 2. colors will be washed out (you in Germany will have this better with PAL than NTSC, but anyway) 3. this destroying of "VGA quality" will cost you the same money, that you can put into small LCD monitor with VGA input (some 17" or 19") 4. higher resolutions will probably not work Jiri Napoleon Commander and SimplEd for CMM2 (GitHub), CMM2.fun |
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| Vampire05 Regular Member Joined: 06/12/2020 Location: GermanyPosts: 88 |
yep, these are good arguments |
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| SimpleSafeName Guru Joined: 28/07/2019 Location: United StatesPosts: 351 |
All good points. I bought the Extron for use with my A4000 on a Sony PVM monitor. It cleaned up the signal quite nicely, and made for a pretty easy connection. Prior to the Extron I was getting a crappy picture, if any at all. Pretty ugly... A "down scalar", if those exist, might be necessary for this application. And +1 on your recommendation for going with a more modern monitor. That's the sane approach. I have one that can handle 15khz as well as the "normal" frequencies, so I get the best of both worlds. You can usually find a compiled list of monitors that support 15Khz at sites such as Lemon64 or Amibay. |
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