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View Full Version : PS1 Scart Sync Issue - LM1881 Related?



ballzdeepx
01-01-2015, 03:03 PM
Hey all,
So I'm down to my last console here that I want to use RGB with, the PS1. Unfortunately, all I get is a rolling screen, so it's not syncing correctly.

My Setup
NTSC PSX system
PVM 2950Q

Scart cable to BNC (with LM1881 built in) goes to my PVM 2950 - Fully Grounded

PSX Scart cable - Pins Populated
RGB Pins all have 220 caps (neg legs facing display/hood)
20 - Composite Video
4 & 21(Hood) - Ground
8 & 16 - 5V bridged with resistor
2 & 6 L/R Audio

Now the PSX AV output only does Composite Sync, and it outputs on pin 6


All of my other scart cables for consoles use composite video for the most part so I don't have a cable that uses this type of sync to test with.

I've also tried moving pin 6 on the psx AV end to 5 which is luma (Y) hoping I could get it to sync off of that but no luck.


I'm wondering if the LM1881 does not like getting fed this type of sync, or maybe the PVM doesn't like the result. It seems to work just fine with cables giving it composite video (thanks to the LM1881).

If I use this same cable into a scart to component converter it works perfect so I'm pretty much out of ideas at this point. I'm debating just using a ps2 with component cables instead.

Thanks in advance!

skate323k137
01-01-2015, 03:05 PM
FWIW I use a lm1881 successfully with composite video input from a PS1, however, I don't power it from the AV cable. I tapped voltage from inside the playstation, since my cable didn't have the 5v wired at the multi out.

ballzdeepx
01-01-2015, 03:17 PM
Interesting.
Does your cable by chance have pin 8 (video ground) from the AV end going to ground in the scart hood on pin 17?

That's the only other thing I can think of that could be wrong (my cable doesn't have anything on pin 8 on the AV side or 17 on the scart side), I know some PSX scart cables have that composite guncon crap inline.

Xian Xi
01-01-2015, 04:08 PM
Sounds like your not getting power to the LM1881.

ballzdeepx
01-01-2015, 04:26 PM
I'll doublecheck that thanks. Pin 10 on the PS AV side is definitely connected to pin 8 on the scart though. I am using a 220ohm resistor to bridge to 16 for now, but it's the same with or without using a resistor at all.

ballzdeepx
01-01-2015, 04:52 PM
Ok I measured Pin 8 and 16 and they both measure 5v so the stripper should be getting power. I also tested with a saturn cable and removed 5v, it didnt work, - replaced 5v worked, so it would seem the stripper is working.

skate323k137
01-01-2015, 05:03 PM
Mine is not a scart cable, but the shielding of the video (video ground) is common with the power ground for the lm1881.

I'm using an old gamestop cable that has both component and composite plugs, so I get RGB and cvid, then I just made my own little lm1881 in a box that's powered from tapping the psx psu. The ground for the lm1881 is tied to video ground.

if your lm1881 is in the breakout, check where it's grounded to, and make sure that pin is grounded in the psx cable.

ballzdeepx
01-01-2015, 05:11 PM
Makes sense. Yeah, this cable doesn't even have ground shielding just two ground cables from the AV connector (pins 1 and 3 which are bridged to the shield metal on the av connector)
Maybe I just need to piggyback a wire from pin 8 of the AV connector to one of the grounds?

skate323k137
01-01-2015, 05:17 PM
This might help, make sure all the proper pins are all grounded

http://members.optusnet.com.au/eviltim/gamescart/psx.png

ballzdeepx
01-01-2015, 05:19 PM
Thanks skate, I actually did follow that to a T and it didn't help. I daisy chained all grounds that were in the diagram but still no luck.

One thing I've not seen a concrete answer on, does passing Csync or pure sync through a lm1881 work/matter?
If anything I'd think it would just clean things up that much more but not hinder anything.

Xian Xi
01-02-2015, 12:43 AM
Are you by chance using an extension cable in between? Don't forget that most extensions have input to output for sync aka Pin 19 to pin 20.

Pasky
01-02-2015, 12:43 AM
I have a LM1881 tucked in my PS1 cable works fine. I used Luma as the input. So must be something with your wiring.

ballzdeepx
01-02-2015, 01:26 AM
No extension cables in the mix, just ps1 scart cable to scart switch>scart to BNC cable.
All my console cables have sync on pin 20, scart to BNC cable has sync on pin 19. Pasky do you know if your cable has video ground specifically on pin 17 which goes to pin 8 on the AV connector/console end?

Pasky
01-02-2015, 02:55 AM
I wired mine in the same manner of the picture Skates posted. Sync is going to 20. 8 is wired to 17 on a daisy chain that ties all the grounds together in the scart connector (4,5,9,13,17,18,21). Double check your LM1881 pinout. Double check you've got composite video or luma going to the LM1881's input.

Also just double check everything including all pins on the Lm1881 and make sure you they read like this:

http://i.imgur.com/AP75SwG.png

7, 5, and 3 can be left floating.

ballzdeepx
01-02-2015, 05:08 PM
Thanks for the help guys but at this point I just need to find a new cable. This thing was mangled to begin with, it's the only one that gives me issue and I've tried everything.
I'll have to try and find a decent PS1 scart cable so if anyone has one to spare hit me up.

Appreciated

ballzdeepx
01-17-2015, 06:13 PM
Well,
I received a newer scart cable and now I get blinking like crazy. Strangely enough if i switch the tv to component its rock solid, but the colors are all off (understandable)
I've tried every resistor I had, caps, a pot to see if it was a resistance issue, but the video just keeps blinking and never holds, be it PS1 or PS2.

Not quite sure what else it could be at this point.

PunkicCyborg
01-17-2015, 06:23 PM
I havent had any problems getting my ps1 to sync with my xm29, xm37 or my old 12" pvm that both need an lm1881 that i just installed in my breakout cable and powered by 5v on pin 8 so I know it is possible to work with that sent up

grendelrt
01-17-2015, 07:43 PM
Well,
I received a newer scart cable and now I get blinking like crazy. Strangely enough if i switch the tv to component its rock solid, but the colors are all off (understandable)
I've tried every resistor I had, caps, a pot to see if it was a resistance issue, but the video just keeps blinking and never holds, be it PS1 or PS2.

Not quite sure what else it could be at this point.

My PS2 was constantly blinking, pic would drop and then come back. It was the only console of the 5 hooked up that was having the issue. I ended up removing a couple resistors on the my scart switch (Bandridge) that were known to cause a very small power draw and it fixed the issue. Only my PS2 had the issue so I believe it needed just a little more power on the lm1881 than my other systems. I know you are using a PS1 but sounds very similar to my issue.

ballzdeepx
01-18-2015, 07:08 PM
Thanks guys, the power thing kind of make sense to me but at this point I'm just going to run it from scart>component converter. It looks 99% as good as RGB on the pvm anyways so I'll just stick with that. Maybe the extra +5v from that is what's keeping the image stable.

Wachenroder
02-24-2015, 08:47 PM
I just ordered an SCART cable for my PS1. I'm working with an 8041, I'm gonna keep this thread in mind in case I have problems.