Yet another LM1881 question - black picture

[Rablador]

Hi!

Hooked up an LM1881 chip to all necessary inputs and outputs:

Pin -
#1 Composite/H-sync out -> Composite/H-sync on monitor
#2 Composite video in
#3 V-sync out -> V-sync on monitor
#4 Ground -> Pin #6 on chip and ground on input source

#5 N/A
#6 Ground -> Pin 4 on chip and ground on input source
#7 N/A
#8  +5-12V in

http://www.gamesx.com/grafx/lm1881.gif

I have connected +5V ground and video ground on input source.
R,G,B have 220 microF capacitors.

What I get is a black picture with no disturbance at all. The monitor makes a "sync" sound, but no picture appears. Have tried both a PSX and a DC rgb cable.

Any clues?

[NFG]

You didn't mention the resistor and capacitors on pins 2 and 6.  These are not optional parts.

If your monitor is syncing (or at least sounds like it is) then it's possible your RGB lines are at fault.  Check that you're not using a SCART pinout for a Japanese RGB cable or something else ridiculous. 

[Rablador]

Ah, sorry, the caps and the resistor are there.

I'm using a regular Euro SCART and I've also checked that the pins are correct.

Attached a photo.

[zedrein]

I'm the local idiot around here so don't take what I say as fact, but are you sure you're wiring the resistor and cap on pin #6 correctly? (cap in parallel and resistor in series, maybe vice versa) And it appears as though you've got the cap on pin #2 right -- If nothing else this will just bump your thread to the front again  

[viletim]

Rablador,

Check grounds - is the SCART pin you are using as ground actually connected in the cable?
Check power - where does the 5V DC come from?

[Rablador]

Zeid:
This is how I wired it:

                ----cap----
Pin #6---                  --------ground
               ---resist---

Is it correct?


Vile:
The Video (composite) ground and +5V ground from the PSX are connected. Pin #6 and #4 are connected. Then I simply connected all four of them. Finally, from that bunch I led one cable to the ground on the monitor.

The 5V is taken from the switching pin #8 on the scart, meaning #10 on the PSX. I get a reading of 5.02V on the multimeter.

What do you think?

[zedrein]

For reference, I always use this photo when wiring up my LM1881:

[Rablador]

Nice photo, thanks!

However, it seems I am doing the exact same thing... What are you using as a 5V source?

[RGB32E]

Nice photo, thanks!

However, it seems I am doing the exact same thing... What are you using as a 5V source?

Which monitor are you connecting a DC and PSX to?  Is a LM1881 required?  The DC outputs composite sync. 

What happens if you remove the capacitors on the RGB lines?  Are the capacitors connected with the correct polarity?

[Rablador]

It's a Wei-Ya multi-sync monitor which I know is not happy with 15kHz sources. I have an upscaler to VGA for troublesome PCBs. I tried connecting the PSX directly to both (without the LM chip), but that did not work.

Haven't tried removing the caps as I am planning to keep the RGB cable as-is. You think it'd make a difference? The caps are left as-is in the psx scart housing. From there I'm using a female scart with the LM chip (with R,B,G going straight to the monitor), so I believe everything should be ok.

[Rablador]

Here's an update:

Tried my rig on a 1084S RGB monitor and everything seems to be working well. Using only Video Ground (disconnecting the +5V Ground) makes no difference.

I tried putting the output composite sync on the Hsync on the monitor, but the screen turned into horizontal lines and a lot of flicker. Is my setup still having problems? The composite sync obviously works, but shouldn't the Hsync on the monitor work as well? Or maybe the 1084S require strict Hsync for that pin...

[RGB32E]

Here's an update:

Tried my rig on a 1084S RGB monitor and everything seems to be working well. Using only Video Ground (disconnecting the +5V Ground) makes no difference.

I tried putting the output composite sync on the Hsync on the monitor, but the screen turned into horizontal lines and a lot of flicker. Is my setup still having problems? The composite sync obviously works, but shouldn't the Hsync on the monitor work as well? Or maybe the 1084S require strict Hsync for that pin...

Ugg... why do you even bother with a 1084S!?  If you live in the states, save yourself a lot of trouble and purchase a Sony PVM off of Craigslist!!! No sync separator needed! 

[Rablador]

Nono, that was just for reference, to see if the setup works at all.

Conclusion:
Composite sync - works
Composite sync as Hsync - not working?