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AuthorTopic: CRT and VGA displays simultaneously on stock A1200?  (Read 2014 times)

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Offline paul1981

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #15 on: August 19, 2019, 08:10:49 PM »
Could be a difference between the Indivision 1200 Mk.I and Mk.II regarding the disablement of the video port? Someone must know a definitive answer here. I was under the impression the video output port wasn't affected.
 

Offline A1200Dude

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #16 on: August 22, 2019, 05:35:07 AM »
Ok so it seems like the issue is indeed having a PAL Amiga connected via composite to an NTSC monitor, which as a result will only display the image in black and white. Before I completely give up on this and go the RGB route and swap cables constantly, would something like this work to bridge the PAL/NTSC issue:

THE CIMPLE CO - NTSC to PAL Converter Kit - TV Converter from PAL to NTSC - Bi-Directional TV System Converter Adapter with Two RCA Cables - (White) - Does NOT Convert Actual DVD OR VHS, ONLY Output https://www.amazon.com/dp/B07RHQKHWD/ref=cm_sw_r_cp_tai_GMHxDb3E6MZVF

Could this indeed convert the PAL composite signal coming out of the Amiga and turn it into a full-color NTSC composite signal that the Commodore 1080 monitor could properly display?
 

Offline Motormouth

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #17 on: August 24, 2019, 04:12:13 PM »
Ok so it seems like the issue is indeed having a PAL Amiga connected via composite to an NTSC monitor, which as a result will only display the image in black and white. Before I completely give up on this and go the RGB route and swap cables constantly, would something like this work to bridge the PAL/NTSC issue:

THE CIMPLE CO - NTSC to PAL Converter Kit - TV Converter from PAL to NTSC - Bi-Directional TV System Converter Adapter with Two RCA Cables - (White) - Does NOT Convert Actual DVD OR VHS, ONLY Output https://www.amazon.com/dp/B07RHQKHWD/ref=cm_sw_r_cp_tai_GMHxDb3E6MZVF

Could this indeed convert the PAL composite signal coming out of the Amiga and turn it into a full-color NTSC composite signal that the Commodore 1080 monitor could properly display?

Interesting, All my RGB (1084) monitors (two P and one D variants) can display 60 Hz NTSC and 50 Hz Pal without any issues, most of the, Monitors of this generation can handle both 50 Hz and 60 Hz signals.  The image may need to be resized if one display Pal on NTSC or visa versa.
(as Pal is longer vertically).  However this is not an issues with colors.  The NTSC and PAL color gamut are almost the same.

The video issue that typically occurs with PAL on an NTSC television (or visa versa) where the TV can only handle one frequency, is image rolling.  IE the image rolls vertically as the image does not properly sync or the image does not sync at all and you would not see anything then.

If you have a Amiga OS 2.0 or greater change the Amiga into NTSC mode in early startup menu.
Another thing is that you can jumper the A1200 and make it default into NTSC mode.

 

Offline Motormouth

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #18 on: August 24, 2019, 05:19:36 PM »
Oh,  I just though of another thing that might be happening,  on the 1084s there is a switch that changes the monitor from composite to Y/C mode for the monitor's RCA input.
Maybe your monitor. is set to Y/C mode rather than composite mode.  If the composite signal is put into the Y (luminescence) all you would see is black and white.
« Last Edit: August 24, 2019, 05:21:20 PM by Motormouth »
 

Offline A1200Dude

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #19 on: August 24, 2019, 06:18:28 PM »
There is a switch on the front of the 1080 for "comp." and "sep." and inputs on the back for "video" and "chroma." I've tried every combination amongst those four, and still no color composite signal shows, only B&W when on the "video" input ("chroma" displays nothing).

I'm intrigued by what you said here: "Another thing is that you can jumper the A1200 and make it default into NTSC mode."

Is this easy to do? Will this then display an NTSC color signal out of the composite port, or merely make the unit think it's NTSC but video would be unchanged?

If I can't get the composite to work properly, I am back at square one in terms of needing to split the RGB port. Can't believe this is proving to be as hard/rare as it is.
 

Offline paul1981

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #20 on: August 24, 2019, 06:47:23 PM »
I'm almost certain you can't make a PAL amiga into an NTSC amiga or vice versa without replacing the RF-Composite circuitry. They are different systems, besides having slightly different clocks and the 50/60Hz issue (or non issue, because as mentioned, monitors will display 50/60Hz anyway).
As for the dual screen with the Indivision, I really thought that Amigakit would have given us a hand here as they have been dealing with them for years and years. Hello AmigaKit? Are you there?  ;D
 

Offline Motormouth

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #21 on: August 24, 2019, 10:47:37 PM »
I'm almost certain you can't make a PAL amiga into an NTSC amiga or vice versa without replacing the RF-Composite circuitry. They are different systems, besides having slightly different clocks and the 50/60Hz issue (or non issue, because as mentioned, monitors will display 50/60Hz anyway).

It looks like you are correct paul1981


According to

http://www.wonkity.com/~wblock/a1200/a1200.html

"Q. Is there an internal jumper on the A1200 to set it to default to PAL or NTSC video?

A. No, but if you're really motivated, you can rig this up. My thanks to Tetsuo Oda and Byron Montgomerie, who provided the information that connecting pin 41 of the Alice custom chip to ground causes the A1200 to default to NTSC, while pulling this pin high (disconnecting it from the motherboard and connecting it to +5V through a 4.7k resistor) will make the default power-up state PAL. I would point out that making a modification like this on a surface-mount chip is difficult at best, and you may end up needing an expensive motherboard replacement, or, at worst, a dead A1200 that needs an expensive replacement motherboard available. In most cases, using the boot menu (obtained by pressing both mouse buttons on power-up or reset) to switch to PAL is sufficient. However, with some games, the hardware patch will be necessary to insure proper timing (changing to PAL via the boot menu might make a 50 Hz game run at 60 Hz timing, or vice versa). "

Sorry, for the miss info, the A2000, A3000, A4000 all have regular NTSC/PAL jumpers
The A500 has a easy to install jumper wire in the later models, but it looks like the A1200 is not so easy

The A1200 is the only common amiga I don't have.
 

Offline Motormouth

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #22 on: August 24, 2019, 11:04:01 PM »
There is a switch on the front of the 1080 for "comp." and "sep." and inputs on the back for "video" and "chroma." I've tried every combination amongst those four, and still no color composite signal shows, only B&W when on the "video" input ("chroma" displays nothing).

I'm intrigued by what you said here: "Another thing is that you can jumper the A1200 and make it default into NTSC mode."

Is this easy to do? Will this then display an NTSC color signal out of the composite port, or merely make the unit think it's NTSC but video would be unchanged?

If I can't get the composite to work properly, I am back at square one in terms of needing to split the RGB port. Can't believe this is proving to be as hard/rare as it is.

I would expect the 1080 set to "comp." the composite RCA signal to "video" would be the correct combo. (note: I do not have a 1080 so I would get this verified by someone who does.)

I suggest checking the capacitors in your A1200 To make sure none of them are blown.

If anyone is interested A500 and A2000 the "composite" output is grayscale.   Back in the day If you wanted full color composite from the A500 or the A2000 you needed an A520 (the NTSC and PAL A520 are different units and not compatible) or some type of genlock.


« Last Edit: August 24, 2019, 11:18:01 PM by Motormouth »
 

Offline paul1981

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #23 on: August 25, 2019, 11:29:28 AM »
Back in the day If you wanted full color composite from the A500 or the A2000 you needed an A520 (the NTSC and PAL A520 are different units and not compatible) or some type of genlock.

Exactly, the PAL/NTSC circuitry is still different when built into the motherboards too.  ;)
 

Offline A1200Dude

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #24 on: August 25, 2019, 05:49:21 PM »
I've had a couple of other thoughts that might be potential solutions...

A DB25 switch box like this to use with the Amiga RGB port (that way, each monitor gets its proper full RGB output):
https://www.amazon.com/CablesOnline-Parallel-Printer-Rotary-SB-001/dp/B00E6SQL46/ref=sr_1_8?keywords=db25+switch+box&qid=1566750732&s=gateway&sr=8-8

...assuming that the 23-pin cables for both displays would still fit in the DB25 connector, albeit without locking into place, and that all the proper wiring would passthrough correctly.

OR...a VGA-to-composite adapter:
https://www.amazon.com/dp/B002PXFJ2O/?coliid=I19T8GABAQG631&colid=2TGZ79CDNNMPT&psc=1&ref_=lv_ov_lig_dp_it

...which would come off of a VGA splitter connected to the 23-pin to 15-pin VGA adapter, and then go into the composite on the 1080.

I did order the 15-pin VGA to 9-pin RGB cable I referenced originally, figured if it doesn't work I'll just sent it back. But I'm thinking that the switch box idea would definitely be ideal, as both monitors would be hooked up via RGB then. Has anyone ever used a switch box like that to drive two Amiga displays? Or would this not be doable due to the Amiga's sensitivity to hot-swapping?
« Last Edit: August 25, 2019, 05:52:54 PM by A1200Dude »
 

Offline Motormouth

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #25 on: August 27, 2019, 12:17:40 AM »
What about a pal genlock with a passthrough?

Genlock's, at least on this side of the pond, are fairly cheap, particularly since the advent of DTV standards.
« Last Edit: August 27, 2019, 12:25:37 AM by Motormouth »
 

Offline paul1981

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #26 on: August 28, 2019, 12:17:30 AM »
Has anyone ever used a switch box like that to drive two Amiga displays? Or would this not be doable due to the Amiga's sensitivity to hot-swapping?

No, never used one. Isn't hot swapping only a problem if you're a clumsy git and short out signals to the edge of the connector?  ;D
The one you linked too looks cheap enough, and if it doesn't work couldn't you send it back anyway for a refund?
 

Offline A1200Dude

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #27 on: September 17, 2019, 05:30:43 PM »
Revisiting this...

So I think I will likely go the DB25 switch box route, but would something like this also do the trick?...

https://www.amazon.com/DB25-Female-Male-Cable/dp/B0743YH9TZ/   (This would be preferable as both monitors could then display simultaneously as needed, vs. one or the other with the switch box.)

With either method, I plan on slicing off two pins and part of the DB25 connectors so that the DB23 Amiga connectors fit. Does it matter which two pins (left or right side) get the axe?
« Last Edit: September 17, 2019, 05:39:18 PM by A1200Dude »
 

Offline Oldsmobile_Mike

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #28 on: September 17, 2019, 10:19:26 PM »
In the mid-'90s I had three monitors hooked up to my A1200.  Two on the desk (through 23-pin port and VGA scan doubler 15-pin port) and one at the foot of the bed (through composite output).  Two monitors on a desk was pretty unheard of at the time.  My friends would ask me why I had two monitors... I'd say "Because I have two eyes, of course!"  LOL.  :D
Amiga 500: 2MB Chip|16MB Fast|30MHz 68030+68882|3.9|Indivision ECS|GVP A500HD+|Mechware card reader + 8GB CF|Cocolino|SCSI DVD-RAM
Amiga 2000: 2MB Chip|136MB Fast|50MHz 68060|3.9|Indivision ECS + GVP Spectrum|Mechware card reader + 8GB CF|AD516|X-Surf 100|RapidRoad|Cocolino|SCSI CD-RW
 Amiga videos and other misc. stuff at https://www.youtube.com/CompTechMike/videos
 

Offline paul1981

Re: CRT and VGA displays simultaneously on stock A1200?
« Reply #29 on: September 18, 2019, 07:49:05 PM »
Revisiting this...

So I think I will likely go the DB25 switch box route, but would something like this also do the trick?...

https://www.amazon.com/DB25-Female-Male-Cable/dp/B0743YH9TZ/   (This would be preferable as both monitors could then display simultaneously as needed, vs. one or the other with the switch box.)

With either method, I plan on slicing off two pins and part of the DB25 connectors so that the DB23 Amiga connectors fit. Does it matter which two pins (left or right side) get the axe?

No, but you'd have to cut the same side off of all three plugs of course. I'm not sure what happens about loading the video output with two monitors, whether there'd be degradation.

EDIT: Before you do any cuts, might be best to check with an ohm meter!
« Last Edit: September 18, 2019, 07:56:44 PM by paul1981 »