rgb interference after installing idefix

Glen M · 23 May 2017, 23:40

Tonight I installed my idefix and routed an ide cable out through the case to a cdrom drive. When the drive it powered on and connected to the ide ribbon I'm getting terrible interference on the video signal with lines scrolling vertically in the screen. If I pull out the ide cable the problem goes away. I've tried shielding the cable with some tinfoil (All I have to hand right now) but it makes no difference. Same problem persists when I try a ide hdd rather than the cdrom.

Any suggestions on how to cure it?

Daedalus · 24 May 2017, 00:06

Hmmm, first guess would be that there's a power issue - how are the drives you connect powered?

Glen M · 24 May 2017, 00:16

The cdrom is powered externally. Would I be better trying to power it from the amiga? My thought was trying to not put to much load on the amiga psu.

Edit. I'm wondering if the cdrom drive is causing interference on old caps? All the caps that need replacing are in the area.of the rgb port. Recapping is on my list but I wonder if this is a sign of possible failure?

Daedalus · 24 May 2017, 00:24

No, you're doing it right, but that rules my theory out regarding the power. A stressed power supply can introduce ripples and sags on the 5V line which often show up as noise in the video, but that won't be the case here. Possibly digital interference from the IDE cable running near the video components, or I have a vague recollection of there being issues with some A1200s that caused video noise when certain things happened - I thought that was the floppy though!

Anyway, does it help to route the IDE cable away from the chips on the motherboard? The video encoder is to the left of the IDE port so your cable might be running directly over it.

Glen M · 24 May 2017, 00:28

The idefix is sitting directly over it but lifting it vertical doesn't affect the noise on the screen. I'll try a longer ide cable and try to move the idefix. Further from the board.

I wonder if it could be a ripple current coming from the cheap Molex psu I got on ebay. It and the amiga both plugged into the same extension lead. Unlikely but might be worth a try using a different wall socket.

Daedalus · 24 May 2017, 00:41

If there's no effect at all from moving the IDEFix board around and away from the motherboard, then a longer cable is unlikely to help. The PSU could still be causing it I guess, but I just don't think it's that likely since there won't really be much more of a power draw when the drive isn't powered from the same supply. Is the noise constant or just when the drive is accessed? Any chance of a video of the interference?

Glen M · 24 May 2017, 00:56

It'll be tomorrow night before I could get a video done. It's like a rolling bar of noise. Drive access etc doesn't seem to affect it.

I'll have a play with some ideas tomorrow. The noise was worse when I connected the ide hdd so I'll maybe try another cdrom drive too just to see if it helps. I'll also try a composite video connection to see if it too shows interference. I could always pull the side off my pc and power the cdrom drive from it's atx psu which should elimate any doubts about power.

Glen M · 24 May 2017, 12:32

A couple of screen shots of the interference. I will try to get a video uploaded later and also report back on my tests.

Its easist to see when she first boots. The lines scroll vertically.

And just for completeness a pic of were the IDEFix board is located and the direction of the ribbon cables.

Glen M · 24 May 2017, 20:13

I've fixed it, well sort of fixed it.

The problem was indeed power. If I plug the monitor (of all things) into a different socket all goes back to normal. The bad thing though as wgere the amiga is located I only have 1 single socket so a rethink of the room is in order.

Mad-Matt · 24 May 2017, 21:00

I used to have a similar issue when using a scandex scandoubler. I would have a barely visible blue streaks running horizontally through the middle of the screen. I was able to minimise it by adding a grounding wire from the vga port to the amiga shielding. Not completely gone, but it helped.

Daedalus · 24 May 2017, 21:54

Wow, well it sounds like a grounding issue of some sort so. What might help is to use a good mains noise suppressing extension cord for one of the parts. The monitor might be producing a lot of noise due to the power supply or backlight inverter, and if your sockets or the plugs are old it might not be grounding properly either.

23 May 2017, 23:40	#1
Glen M Registered User Join Date: May 2017 Location: Belfast Posts: 750	rgb interference after installing idefix Tonight I installed my idefix and routed an ide cable out through the case to a cdrom drive. When the drive it powered on and connected to the ide ribbon I'm getting terrible interference on the video signal with lines scrolling vertically in the screen. If I pull out the ide cable the problem goes away. I've tried shielding the cable with some tinfoil (All I have to hand right now) but it makes no difference. Same problem persists when I try a ide hdd rather than the cdrom. Any suggestions on how to cure it?

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24 May 2017, 00:06	#2
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	Hmmm, first guess would be that there's a power issue - how are the drives you connect powered?

24 May 2017, 00:16	#3
Glen M Registered User Join Date: May 2017 Location: Belfast Posts: 750	The cdrom is powered externally. Would I be better trying to power it from the amiga? My thought was trying to not put to much load on the amiga psu. Edit. I'm wondering if the cdrom drive is causing interference on old caps? All the caps that need replacing are in the area.of the rgb port. Recapping is on my list but I wonder if this is a sign of possible failure?

24 May 2017, 00:24	#4
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	No, you're doing it right, but that rules my theory out regarding the power. A stressed power supply can introduce ripples and sags on the 5V line which often show up as noise in the video, but that won't be the case here. Possibly digital interference from the IDE cable running near the video components, or I have a vague recollection of there being issues with some A1200s that caused video noise when certain things happened - I thought that was the floppy though! Anyway, does it help to route the IDE cable away from the chips on the motherboard? The video encoder is to the left of the IDE port so your cable might be running directly over it.

24 May 2017, 00:28	#5
Glen M Registered User Join Date: May 2017 Location: Belfast Posts: 750	The idefix is sitting directly over it but lifting it vertical doesn't affect the noise on the screen. I'll try a longer ide cable and try to move the idefix. Further from the board. I wonder if it could be a ripple current coming from the cheap Molex psu I got on ebay. It and the amiga both plugged into the same extension lead. Unlikely but might be worth a try using a different wall socket.

24 May 2017, 00:41	#6
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	If there's no effect at all from moving the IDEFix board around and away from the motherboard, then a longer cable is unlikely to help. The PSU could still be causing it I guess, but I just don't think it's that likely since there won't really be much more of a power draw when the drive isn't powered from the same supply. Is the noise constant or just when the drive is accessed? Any chance of a video of the interference?

24 May 2017, 00:56	#7
Glen M Registered User Join Date: May 2017 Location: Belfast Posts: 750	It'll be tomorrow night before I could get a video done. It's like a rolling bar of noise. Drive access etc doesn't seem to affect it. I'll have a play with some ideas tomorrow. The noise was worse when I connected the ide hdd so I'll maybe try another cdrom drive too just to see if it helps. I'll also try a composite video connection to see if it too shows interference. I could always pull the side off my pc and power the cdrom drive from it's atx psu which should elimate any doubts about power.

24 May 2017, 12:32	#8
Glen M Registered User Join Date: May 2017 Location: Belfast Posts: 750	A couple of screen shots of the interference. I will try to get a video uploaded later and also report back on my tests. Its easist to see when she first boots. The lines scroll vertically. And just for completeness a pic of were the IDEFix board is located and the direction of the ribbon cables.

24 May 2017, 20:13	#9
Glen M Registered User Join Date: May 2017 Location: Belfast Posts: 750	I've fixed it, well sort of fixed it. The problem was indeed power. If I plug the monitor (of all things) into a different socket all goes back to normal. The bad thing though as wgere the amiga is located I only have 1 single socket so a rethink of the room is in order.

24 May 2017, 21:00	#10
Mad-Matt Longplayer Join Date: Jan 2005 Location: Lincoln / UK Age: 44 Posts: 1,846	I used to have a similar issue when using a scandex scandoubler. I would have a barely visible blue streaks running horizontally through the middle of the screen. I was able to minimise it by adding a grounding wire from the vga port to the amiga shielding. Not completely gone, but it helped.

24 May 2017, 21:54	#11
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	Wow, well it sounds like a grounding issue of some sort so. What might help is to use a good mains noise suppressing extension cord for one of the parts. The monitor might be producing a lot of noise due to the power supply or backlight inverter, and if your sockets or the plugs are old it might not be grounding properly either.

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