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B-Series on RGBI Monitor?

billdeg

Technician
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Nov 18, 2003
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Landenberg, PA USA
The Protecto monitor that sold with the later B series' is a US International VM 1230. I'd try to find a something similar for your B. Monochrome. It's hard to differentiate the single quote character from the double quote characters unless you have a nice sharp monochrome monitor. I have tried a lot of cbm monitors never found a better display than the VM 1230.
 

jac_goudsmit

Experienced Member
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Apr 4, 2012
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Location
Arizona
In case you're interested, here's a link to the service manual for the Philips CM8833 which (as I said in the other thread) I think is identical or very similar to the 1084S: http://www.msxarchive.nl/pub/msx/mirrors/hanso/service_manuals/philipscm8833sm.pdf

It has a nice page with the TTL-RGBI schematic which should help you connect it to your Commodore.

By the way this is a monitor for TV frequencies (~15kHz line frequency), not for VGA or scan doublers.

I really think it should be possible to connect your B128 to the 1084S.

===Jac
 

vwestlife

Veteran Member
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May 2, 2008
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5,174
Location
central NJ
I found the specs for the Apple IIe/IIc color monitor:

14" diagonal
0.52mm slot pitch
high contrast black matrix
50-75 watt power draw

scanning frequencies 15.734 kHz / 60 Hz
bandwidth monochrome text NTSC 8.0 MHz
bandwidth color graphics NTSC 3.0 MHz
composite sync negative 1.0 +-0.5 volts Vpp / 75 ohm

That's the secret of why Apple II color monitors can display such clear monochrome 80-column text: the video bandwidth is increased to 8 MHz when an NTSC color burst is not detected. That's almost as good as Apple's monochrome composite monitors, which were rated at 10 and 12 MHz bandwidth, for the IIe and IIc versions, respectively.
 

patscc

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Apr 13, 2005
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Stevens Point, Wisconsin
Does anyone have a schematic of the Apple II color monitor in question ?
I can see the spec as specifying bandwidth for different circuit groups, but you typically don't change the bandwidth "on the fly" of a video circuit (at least, not 25+ years ago), and I'd be interested in taking a peak at the schematic to see if in fact the specs might be referring to the luminance and chroma circuits, respectively.
patscc
 

KevinO

Experienced Member
Joined
Apr 13, 2012
Messages
341
Location
Des Moines, IA USA
In case you're interested, here's a link to the service manual for the Philips CM8833 which (as I said in the other thread) I think is identical or very similar to the 1084S: http://www.msxarchive.nl/pub/msx/mirrors/hanso/service_manuals/philipscm8833sm.pdf

It has a nice page with the TTL-RGBI schematic which should help you connect it to your Commodore.

By the way this is a monitor for TV frequencies (~15kHz line frequency), not for VGA or scan doublers.

I really think it should be possible to connect your B128 to the 1084S.

===Jac

I've got the service manuals for both the Commodore and the NAP versions, but thanks!
 

KevinO

Experienced Member
Joined
Apr 13, 2012
Messages
341
Location
Des Moines, IA USA
The Protecto monitor that sold with the later B series' is a US International VM 1230. I'd try to find a something similar for your B. Monochrome. It's hard to differentiate the single quote character from the double quote characters unless you have a nice sharp monochrome monitor. I have tried a lot of cbm monitors never found a better display than the VM 1230.

Interesting, I just looked it up, and it looks almost exactly like one I just saw. It's a National Electronics M1200 monochrome monitor. It's at one of my clients, and I've got queries out as to whether or not I can take it. I'm not entirely sure it works. Turning up sub-bright gives only a dim raster, which may or may not mean anything. It doesn't have RCA but only BNC connections, but that's easy to fix.
 

vwestlife

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May 2, 2008
Messages
5,174
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central NJ
Ok, I thought this was going to be easy. I thought that with the right cable, I could connect my B128-80 to a Magnavox 1084 or another Magnavox 80 monitor I have available. The composite output on the B128 is terrible, so I wanted to use the RGBI connector.

Another thought, since I just happen to be using my 1084 monitor right now: have you tried connecting the B128's composite output to the 1084 (or other similar Commodore model) monitor, and then switching the monitor into Luma-Chroma (LCA) mode? Connect it to the monitor's Luma input. Without anything connected to the Chroma input, this effectively turns it into a hi-res monochrome composite monitor (with a color picture tube), since in Luma-Chroma mode, the monitor is not restricting its video bandwidth down to 3 MHz in order to filter out the NTSC subcarrier.
 

KevinO

Experienced Member
Joined
Apr 13, 2012
Messages
341
Location
Des Moines, IA USA
Another thought, since I just happen to be using my 1084 monitor right now: have you tried connecting the B128's composite output to the 1084 (or other similar Commodore model) monitor, and then switching the monitor into Luma-Chroma (LCA) mode? Connect it to the monitor's Luma input. Without anything connected to the Chroma input, this effectively turns it into a hi-res monochrome composite monitor (with a color picture tube), since in Luma-Chroma mode, the monitor is not restricting its video bandwidth down to 3 MHz in order to filter out the NTSC subcarrier.

Well, I'll be damned. Vwestlife, you nailed it. Look at this:

P1030221.jpgP1030222.jpg

EDIT: This us a test. Nice...
 
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