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All I want is a monitor


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I'm a bit confused by the 'sync on green'. You are trying to connect an color Apple monitor designed for an Apple II, right? That isn't that the AppleColor RGB monitor for the Apple IIGS, which is an analog monitor (I'm getting this info from wikipedia - Apple displays - Wikipedia , so it may be BS). which has a separate composite sync pin not connected to the green signal, as shown below.

 

 

 

 

 

 

AppleIIGS RGB.gif

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On 12/28/2020 at 12:09 PM, Doug_in_NC said:

I'm a bit confused by the 'sync on green'. You are trying to connect an color Apple monitor designed for an Apple II, right? That isn't that the AppleColor RGB monitor for the Apple IIGS, which is an analog monitor (I'm getting this info from wikipedia - Apple displays - Wikipedia , so it may be BS). which has a separate composite sync pin not connected to the green signal, as shown below.

 

 

 

 

 

 

AppleIIGS RGB.gif

I may be confused, but I thought I saw a pinout on an Apple II site that said it had sync on green. Potatohead, is it possible to connect the composite sync right out of the transistor in your circuit, and still have it on green? ( I'm trying for maximum compatibility here. Tired of having dozens of monitors available, none compatible).

 

I've seen monitors and video outputs something like this:

 

R

G with composite sync

B

H with composite V

V

 

That *should* work with most 15khz analog monitors other than EGA (inverted sync).

 

This way if I decide to use both the Apple and the CoCo at the same time I might still be able to see what I'm doing.

 

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The circuit combines green video info with combined H&V sync.

 

Composite sync is confusing to me.  I take it to mean the sync present on a composite video signal, perhaps with the video information suppressed.

 

It could also mean H&V sync combined into a composite sync only signal.

 

Depending on the source, these could also be the same thing.

 

In 15khz land, they likely are.

 

The circuit I linked here combines H&V sync with the green video information.   IMHO, it should only be used to combine green and already separate H&V sync:

 

G with combined (composite) sync

 

It may work to combine the H&V sync for use on a combined or composite sync only input, but I don't know.  The germanium transistor may need the bit of power to the green signal to work.

 

However, just combining sync can be done with a similar kind of circuit.

 

https://www.retrorgb.com/building-a-passive-sync-combiner.html

 

In all cases, just wiring things together is a bad idea due to the lack of current limiting and the signals being out of spec.

 

If it were me, I would build both and try them.  They are simple enough.

 

If they work, either make a couple different cables, or a little PCB with a switch, or just appropriate connectors.

 

I am not where I can look, but the sync signals on the composite video output are the same signals, but have the video there too.  The only place I would use that signal is:

 

Another composite video input

 

The Y input on a component capable display for a monochrome image.  (A sharp one too)

 

The Y or Luma input on an S-video or Y/C monitor like the Commodore ones.

 

 

 

 

 

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Sorry if responding to an older post is taboo here.  But I have some advice.  There are many solutions and options, but probably the setup of a CoCo 3 with a CRT display (especially a period-authentic one) that strikes a balance between maximum simplicity on the one hand and maximum video quality and compatibility on the other is what CoCo hardware guru Marty Goodman recommended back in August 1987 and what still holds true today:

 

On the Tandy CM-8 monitor: though (being made specifically for the CoCo 3) it's maximum-simple (one connector, no adapters) and does an adequate job at analog graphics, its rendering of 80 column text isn't very crisp, and it renders a huge portion of classic CoCo 1/2 apps (especially games) in black-and-white instead of in their intended artifact colors.

 

Instead, follow these steps:

  1. Get one of several Magnavox analog RGB monitors (list below) that also have composite inputs
  2. Get an adapter (I know I know) which will let your CoCo 3 connect to that monitor's analog RGB input. Cloud-9 Tech is one such company and its adapters are here.
  3. Connect your CoCo 3 to that monitor using BOTH the analog RGB method (via the adapter) AND using a composite cable
  4. Use the RGB input for CoCo 3-native apps and any CoCo 1/2 apps that show in color that way, switching down to composite only for CoCo 1/2 apps that need composite for color.  

These Magnavox monitors are analog, so no analog-to-digital conversion is necessary.  They do the CoCo 3's native 15.7 KHz, plus have the same RGB-A signal (separate and upgoing H and V sync).  So the adapter is pretty straightforward as adapters go, just different shapes and pins.  And the monitors are crisper than the Tandy CM-8 and do a better job at the graphics and text.  Finally they show CoCo 1/2 artifact colors as intended; and pushing a button to switch back and forth from whether you're looking at RGB or composite is no more onerous than using your remote to switch from watching your disc player to your cable/satellite/streaming box/antenna on your current TV.  Here's that list:

  • 8CM515 - probably the most widely-available.  With a 0.42mm stripe width, it has sharper text and graphics than the CM-8's 0.52mm.  But the composite doesn't always work.
  • 1CM135 - also 0.42mm
  • 8CM643 - higher-end, harder to find. 0.39mm stripe width.

Avoid the 8CM505.  Although it is as compatible as the prior three, it is too fuzzy (0.65mm stripe width) to render 80 column text well.  A gamer might not care but you wanted that crisp text.

 

The Commodore 1084 and 1084S are other options (Cloud-9 sells adapters for them too).

 

There are some excellent Sony monitors with both analog RGB and composite, most notably the well-regarded KV-1311CR which has excellent 0.37mm stripe width, but connecting them to the CoCo is more involved than connecting a Magnavox.  The Sony CDP-1302 and NEC Multisync are even higher-quality (0.25 and 0.31mm respectively), but, lacking composite, cannot show artifact colors and thus should be avoided in my opinion.  But maybe you don't care about full-color back compatibility with CoCo 1 and 2 apps, especially games?

 

 

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