All I want is a monitor

[Doug_in_NC]

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.

 

 

 

 

 

 

[potatohead]

Guess he has to tell us which monitor he has?

 

Both Apple and SGI used sync on green.  Could be an early Mac display that will still do 15Khz, in which case he would need the little circuit I put here.

[MrDave]

If you are on a budget annd like to tinker.. alot of modern crts can do rgb with a quick internal mod.. check 8 bit guys youtube for that.. but the onscreen menu of modern crts use rgb !

[KG7PFS]

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.

 

 

 

 

 

 

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.

 

[potatohead]

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.

 

 

 

 

 

[potatohead]

Any luck with this?

 

 

[eightbit]

Why don't you just get a switch-a-roo?

 

http://www.cocowares.com/item.php?nombre=Switch-a-roo

 

I used that into an OSSC and it was the most beautiful Coco3 RGB picture I have ever encountered.

[KG7PFS]

Would an Atari SC1224 work with the CoCo?