Put a scart in your CD32 - Page 2

26 February 2007, 22:48

Composite sync is connected to pin 20, 12v with 150ohm resistor in 16 and video ground 17.

Opinions are welcome

Jope · 27 February 2007, 06:13

I wonder if one ground is enough.. On normal Amigas, there are usually grounds for each colour.

Perhaps it is, if the grounds are all connected together on the TV end.

dambuster · 27 February 2007, 21:17

@Jope
Should be, is that because each wire can/could/should be screened, but ground is ground unless marked as 0v. - i think

patrik · 07 March 2007, 21:39

@cd32asetukset:
Dont forget pin 8, it is often needed. Also, as others suggested - try connecting all video-ground pins on the scart.

09 March 2007, 03:46

@jope, patrick and dambuster

Thanks for all suggets, i need to try this ideas, now im a bit busy.

Spectre · 10 February 2009, 21:42

Hi all. I realise I'm digging up an old thread and I hope that isn't too frowned upon here...

I came across info on the CD32 TP9 port when I first got my CD32 and I've finally decided to tinker with it and try and achieve RGB scart. I have some experience of this kind of modding so thought I'd give it a go.

Firstly, I've confirmed the TP9 pinout from C='s schematic (and a few other places). So far I've connected the red, green and blue lines (scart pins 15, 11 and 7 respectively) and I've attached comp sync to pin 20. I have ground going to each video ground (rgb), the comp sync ground and the metal shield ground (pin 21).

My problem is what to connect to pin 16, to tell the TV the signal is rgb. I've read that vertical sync is used in this way with custom atari st cables and I see from above that Dexther used the composite sync. I've tried composite, horizontal and vertical sync, none of them give me any joy. I see Patrik has suggested a 150ohm resistor off the 12v line, but that doesn't seem quite right to me either, for example, the sega dreamcast uses 12v via a 560ohm resistor to pin 16...

So so far I've got naff all. I'm yet to try 47ohm resistors on each colour line as I don't have any to hand, might take a trip to maplins tommorow, but if pin 16 is right I would have thought I'd get some kind of signal even if the colours are out.

Any input appreciated!

alexh · 10 February 2009, 22:30

Without a signal on pin 16 you will get nothing (black screen).

It is supposed to be a constant voltage input of 1v to 3v.

The value of the resistor is variable depending on the current supply of the input electronics I believe...

Use Ohms law to calculate what value of resistor you need to create a potential divider circuit where the input will be between 1v-3v.

Or just bung any small size resistor down. ;-)

Remember not to dissipate too much heat through a single resistor.

Spectre · 11 February 2009, 10:32

Ok, well I'm going to pop to maplins later and get a few resistors. Have just done a bit of poking around with my multimeter and have found the following:-

12v point outputting 11.9v
TP9 CSynch outputting 3.45v
TP9 VSynch outputting 4.9v
TP9 HSync outputting 4.5v

This would explain why Dexther had success using the comp synch via a 47ohm resistor to pin 16 for rgb. When I first read his post I thought he probably meant resistors on the rgb lines and just typed it out wrong (as he has one on red and green but not on blue), but I guess while fudging around he stumbled upon this solution. His blue must be a bit off if he didn't put a resistor on that line too!? I think the 12v point would make more sense as hopefully the output would be more stable, where as I would expect the synchs to vary depending on what video is being output...

Also, I tested the expansion port pin 174 to ground info (5th pin from the from end on the parts side, nearest TP9), and this does indeed appear to "disable internal video interfaces", i.e. my composite video output all but died (still get a very faint outline) when I connected pin 174 to ground. If and when I get scart working, I'll test to see if this improves the picture.

Spectre · 11 February 2009, 18:58

Ok, well I appear to have fried the video on my CD32 motherboard!! I got as far as 47ohm resistors on each colour line, comp sync to pin 20 and 12v to pin 16 via a 150ohm resistor. Was getting RGB scart, but with sync issues, so my TV would only display the picture for a second or so.

I was experimenting with grounding pin 174 of the expansion port, when the video died. I suspect I managed to connect it to 12v (whoops). I can hear the boot up tune, but I get nothing from comp vid and just a black picture from RF. I don't have a svhs lead to hand to test with, but it appears I have permanently "disabled the internal video interfaces"!

Luckily I can replace the mobo for £12 via ebay so it's not the end of the world. I think the problem is the comp sync isn't at the right spec. It's possible that horiz or vert sync from TP9 might work (given Dexther's success) and I'm fairly sure that comp vid off the yellow rca would do the job as this is how other consoles sync. However, I won't be experimenting any further at this stage as I don't want to risk a second motherboard... svhs will have to do.

alexh · 11 February 2009, 19:29

Never known sync issues... you got a crap TV? Or a new fangled plasma?

Spectre · 11 February 2009, 19:51

6 month old samsung syncmaster lcd. Reading above, I'm not the first person to get this far, cd32asetukset seemed to have the same issue. Imo the comp sync output from tp9 isn't correct for TVs. I think using comp vid from the yellow rca jack instead would solve this.

alexh · 11 February 2009, 19:56

I never used TP9, I soldered directly to the edge connector but it must be the same thing. Works fine on a crappy old CRT TV.

Spectre · 12 February 2009, 14:26

Well a board member has offered me a mobo with rgb mod, so if the deal all goes well I'll check how it has been done and post some info here as there seem to be several different opinions on how best to go about it.

11 February 2009, 10:32	#28
Spectre Registered User Join Date: Feb 2009 Location: Cambridge, UK Age: 44 Posts: 43	Ok, well I'm going to pop to maplins later and get a few resistors. Have just done a bit of poking around with my multimeter and have found the following:- 12v point outputting 11.9v TP9 CSynch outputting 3.45v TP9 VSynch outputting 4.9v TP9 HSync outputting 4.5v This would explain why Dexther had success using the comp synch via a 47ohm resistor to pin 16 for rgb. When I first read his post I thought he probably meant resistors on the rgb lines and just typed it out wrong (as he has one on red and green but not on blue), but I guess while fudging around he stumbled upon this solution. His blue must be a bit off if he didn't put a resistor on that line too!? I think the 12v point would make more sense as hopefully the output would be more stable, where as I would expect the synchs to vary depending on what video is being output... Also, I tested the expansion port pin 174 to ground info (5th pin from the from end on the parts side, nearest TP9), and this does indeed appear to "disable internal video interfaces", i.e. my composite video output all but died (still get a very faint outline) when I connected pin 174 to ground. If and when I get scart working, I'll test to see if this improves the picture. Last edited by Spectre; 11 February 2009 at 13:53.

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26 February 2007, 22:48	#21
cd32asetukset Posts: n/a	Composite sync is connected to pin 20, 12v with 150ohm resistor in 16 and video ground 17. Opinions are welcome

27 February 2007, 06:13	#22
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,938	I wonder if one ground is enough.. On normal Amigas, there are usually grounds for each colour. Perhaps it is, if the grounds are all connected together on the TV end.

27 February 2007, 21:17	#23
dambuster Zone Friend Join Date: Nov 2006 Location: Dundee / Scotland Posts: 151	@Jope Should be, is that because each wire can/could/should be screened, but ground is ground unless marked as 0v. - i think

07 March 2007, 21:39	#24
patrik Registered User Join Date: Jan 2005 Location: Umeå Age: 44 Posts: 953	@cd32asetukset: Dont forget pin 8, it is often needed. Also, as others suggested - try connecting all video-ground pins on the scart.

09 March 2007, 03:46	#25
cd32asetukset Posts: n/a	@jope, patrick and dambuster Thanks for all suggets, i need to try this ideas, now im a bit busy.

10 February 2009, 21:42	#26
Spectre Registered User Join Date: Feb 2009 Location: Cambridge, UK Age: 44 Posts: 43	Hi all. I realise I'm digging up an old thread and I hope that isn't too frowned upon here... I came across info on the CD32 TP9 port when I first got my CD32 and I've finally decided to tinker with it and try and achieve RGB scart. I have some experience of this kind of modding so thought I'd give it a go. Firstly, I've confirmed the TP9 pinout from C='s schematic (and a few other places). So far I've connected the red, green and blue lines (scart pins 15, 11 and 7 respectively) and I've attached comp sync to pin 20. I have ground going to each video ground (rgb), the comp sync ground and the metal shield ground (pin 21). My problem is what to connect to pin 16, to tell the TV the signal is rgb. I've read that vertical sync is used in this way with custom atari st cables and I see from above that Dexther used the composite sync. I've tried composite, horizontal and vertical sync, none of them give me any joy. I see Patrik has suggested a 150ohm resistor off the 12v line, but that doesn't seem quite right to me either, for example, the sega dreamcast uses 12v via a 560ohm resistor to pin 16... So so far I've got naff all. I'm yet to try 47ohm resistors on each colour line as I don't have any to hand, might take a trip to maplins tommorow, but if pin 16 is right I would have thought I'd get some kind of signal even if the colours are out. Any input appreciated!

10 February 2009, 22:30	#27
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,529	Without a signal on pin 16 you will get nothing (black screen). It is supposed to be a constant voltage input of 1v to 3v. The value of the resistor is variable depending on the current supply of the input electronics I believe... Use Ohms law to calculate what value of resistor you need to create a potential divider circuit where the input will be between 1v-3v. Or just bung any small size resistor down. ;-) Remember not to dissipate too much heat through a single resistor.

11 February 2009, 18:58	#29
Spectre Registered User Join Date: Feb 2009 Location: Cambridge, UK Age: 44 Posts: 43	Ok, well I appear to have fried the video on my CD32 motherboard!! I got as far as 47ohm resistors on each colour line, comp sync to pin 20 and 12v to pin 16 via a 150ohm resistor. Was getting RGB scart, but with sync issues, so my TV would only display the picture for a second or so. I was experimenting with grounding pin 174 of the expansion port, when the video died. I suspect I managed to connect it to 12v (whoops). I can hear the boot up tune, but I get nothing from comp vid and just a black picture from RF. I don't have a svhs lead to hand to test with, but it appears I have permanently "disabled the internal video interfaces"! Luckily I can replace the mobo for £12 via ebay so it's not the end of the world. I think the problem is the comp sync isn't at the right spec. It's possible that horiz or vert sync from TP9 might work (given Dexther's success) and I'm fairly sure that comp vid off the yellow rca would do the job as this is how other consoles sync. However, I won't be experimenting any further at this stage as I don't want to risk a second motherboard... svhs will have to do.

11 February 2009, 19:29	#30
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,529	Never known sync issues... you got a crap TV? Or a new fangled plasma?

11 February 2009, 19:51	#31
Spectre Registered User Join Date: Feb 2009 Location: Cambridge, UK Age: 44 Posts: 43	6 month old samsung syncmaster lcd. Reading above, I'm not the first person to get this far, cd32asetukset seemed to have the same issue. Imo the comp sync output from tp9 isn't correct for TVs. I think using comp vid from the yellow rca jack instead would solve this.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

11 February 2009, 19:56	#32
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,529	I never used TP9, I soldered directly to the edge connector but it must be the same thing. Works fine on a crappy old CRT TV.

12 February 2009, 14:26	#33
Spectre Registered User Join Date: Feb 2009 Location: Cambridge, UK Age: 44 Posts: 43	Well a board member has offered me a mobo with rgb mod, so if the deal all goes well I'll check how it has been done and post some info here as there seem to be several different opinions on how best to go about it.