RGB->VGA converter sync issues? [solved]

[newsdee]

I ran across an issue with an RGB->VGA converter and would need some advice to debug.

Works fine on boot, but after 10-15 mins the video starts to wobble (as in losing sync).
OSD of card is stable, so I suspect an issue with the video conversion, or maybe the source itself.

Setup is a JAMMA SuperGun with an SNK MV-1FZ PCB and a 15A arcade power supply.
Online search suggest the issue could be power, but I would think the PSU rating would be enough?

The card is one of these - has anybody experienced this problem before?
 http://www.multicade.ca/product_info.php/pName/cgaega-to-vga-converter/cName/mameconverter-pcbs

[newsdee]

The seller advised to change the "clamp ST" and "clamp SP" settings of the converter.
The manual barely mentions those settings, so not sure what they do, but long story short it didn't help.

I had the card replaced... and the new card has exactly the same problem.
I thought it could be voltage... but no, after measuring I'm outputting 5V (4.98) so that should be OK.

I suppose the last part to check would be the MVS pcb itself.
I guess I need to go out and get another JAMMA pcb to try

[lilshawn]

i would tak another look at the power supply. Maybe consider a seperate supply for the convertor. I know they are pretty steep on the requirements (2 amps (2000mA) @ 5v)

your supply outputs 15A but how much of that is being sucked up by your MVS board?

I would get a seperate plug in type supply and give that a try. (something like this: http://www.dhgate.com/cheap-5v-2a-us-plug-ac-power-adapter-for/p-ff8080813976b29c0139b5a7ffd76eb6.html

[newsdee]

Thanks for the suggestion, I forgot about exploring that route.
Oddly enough that seems to make things worse.   

I've tried both a 5V 3A plug from a USB hub, and a PC power supply (700W - 24A on 5V).
In both cases, the sync is out of since boot - not like before where it starts OK then degrades.

Now maybe the 3A plug is old, and the way I connected to the PSU was a bit wonky.
Didn't have an ATA connector, so I've improvised pins from a couple of nails taped to the wires.
I thought it could have too much resistance, but multimeter shows it's under 2 Ohms, so I guess in theory I could get 2.5A?

Here's how it looks like - every 1-2 secs I get this:

[rCadeGaming]

I would also suspect the power supply, but if you wired it up correctly, a 700W PC power supply should be plenty capable of giving that thing enough smooth power.

Is everything running off the same breaker circuit?  Ground levels among the AC circuits in your house can vary.

Does the scaler specify that it wants exactly 5v?  Are you giving it +5V or -5V?

Does it want AC or DC?  DC is more common, but some things do run on an AC power supply, like the NES, which takes AC from its power supply and converts it DC internally.

What kind of sync will the scaler work with, composite sync/separate HV sync/composite video?  What is getting; I'm guessing composite sync from a NEO GEO board?

Last thing, and this is probably my best guess.  What is the peak to peak voltage of the sync?  The NEO GEO could be putting out a different level than the scaler is designed to work with.  It's hard to tell without an oscilloscope, but you can start with some tests.  If the NEO GEO's sync output is too hot, you can bring it down with some resistors on the line.  Try small resistors and move up, 10ohms, 100ohms, 1kohm.  This may make it look better, but guessing just from your picture it seems more likely that the sync is too weak.  If this is this case it should get worse as you add resistance.  In order to boost it you need to build a simple amp circuit, or see if there's any resistors on the sync as it comes out of the NEO GEO board, or as it goes into the scaler, that you can bypass. 

I'd say confirm some things with the power supply and then try adding resistance on the sync line(s) and see which way it goes.  You can't hurt anything by putting resistors in line, but be careful that you know what you're doing if you start bypassing anything on the boards.

[newsdee]

Thanks for the suggestions!

It seems that it's intermittent now. Not sure what I did, but earlier today it was running fine without issues.
Then, I had to move things around (so disconnect the cable) and now it's starting to happen again (although milder than before).
Not sure what I did, except maybe the sync cable was pushed in more or less than usual? Odd - but I guess I could try reinserting the sync few times to see.

To answer your questions, the card is a GBS-8200 v4.0; it takes DC +5V on input.
It is getting RGB sync from a NEO GEO MVS board (which should be supported)
(manual here http://info-coach.fr/atari/hardware/video/GBS-8200.pdf)

If it's a clue - in addition to the shaking, there are some kind of interference bars and a bit of noise (grain) in the picture.
It doesn't bother me as much as the shaking (looks like an old TV), but could that be a symptom of the sync voltage being too high?

[rCadeGaming]

Is everything running off the same breaker circuit?  Ground levels among the AC circuits in your house can vary.

Did you check this?  The easiest way to be sure everything's running on the same circuit is to use a power strip to get everything running off the same outlet.  This will eliminate any problem here, it's worth ruling it out just to be sure.

...earlier today it was running fine without issues.  Then, I had to move things around (so disconnect the cable) and now it's starting to happen again (although milder than before)...

If it was working perfectly and then you moved it and it got messed up, it possible that there's just a loose connection somewhere.  Rule that out next.  Double check all your connections, make sure everything's inserted all the way, make sure there's no loose components on the GBS board or the NEO GEO board making intermittent contact.  While you're at it check for swelling or leaking capacitors, anything that looks weird on the boards, etc.

It is getting RGB sync from a NEO GEO MVS board...

There's no such thing as "RGB" sync.  RGB just refers to three separate lines containing red, blue, and green color space information, and does not specify what kind of sync is being used.  Horizontal and vertical sync can be transmitted on two more lines.  RGB plus separate H and V is called RGBHV, this is what VGA is.  Instead of separate H and V, composite sync (H and V combined) can be carried on one line.  RGB plus composite sync is called RGBS.  Sometimes composite sync can be added to the green line of RGB instead of using its own line, called sync on green.  Composite video can also be used on its own line as sync.

I'm guessing that your NEO GEO is outputting composite sync on its own line, which the GBS should work fine with.  Its video comes out on five lines right (RGB, sync, and ground)?  How are you physically connecting the video from the NEO GEO to the GBS?

-

My other thought is that I should take back my statement about the 700W power supply being fine.  I've been looking at powering things with ATX power supplies, and apparently bigger is not always better.  The way these things are designed, they can have problems when you're running them on a load of less than 15% of their max rating, which you probably are.  I would look at getting a much smaller one, like what lilshawn suggested.

Didn't have an ATA connector, so I've improvised pins from a couple of nails taped to the wires.

Must not have noticed this before.  This is not the way to troubleshoot.  You can't isolate the problem when you're adding more problems.  Taping things is not a consistent connection.  If you didn't have a connector you should have just cut and soldered.  I wouldn't worry about since you should probably stop using that power supply anyway, but make sure you're making better connections than this in the future.

...could that be a symptom of the sync voltage being too high?

Yeah maybe.  As I said, it's possible it's too high or too low. 

Get everything on the same circuit.
Check all your connections.
Let me know how you're getting video from the NEO GEO to the GBS.
Try combinations of different power supplies and lowering the sync level with resistors to see if it gets better or worse.

Have you ever had the NEO GEO board working on anything else, what if it has a problem itself?

What kind of monitor/tv are you using?

That manual is pretty useless, try finding someone on the shmups forum who knows more about these things.

[newsdee]

Thanks for the detailed reply. I'll definitely recheck the connections; in the meanwhile let me answer some of the other points.

Everything is running from a power strip (since the beginning), so same AC outlet.
In fact the issue seems less pronounced if I use the same power supply.
(but as you said maybe the 700W is overpowered for the purpose)

Signal is RGBS - (five wires, RGB + ground + sync).
They are connected using a pre-built JAMMA harness that I've bought, which has a connector that plugs into the VGA board.

It only worked perfectly once; I loathed to disconnect it but I had to.
It may be the PCB since I've got it from a discarded cabinet that had been outdoors for a few days (no sign of water damage inside though).
I did take a look at the board (removing the MVS plastic cover) but found no obvious burns or damage.

TV is a Samsung LCD, connecting via VGA input.
The VGA adapter's On Screen Display is stable though (while the rest of the picture jumps), so I don't think it's due to the TV itself.

I'm getting a (non NEO-GEO) JAMMA board to test whether the VGA card has the same problem or not.
Once it arrives I'll hopefully be able to rule out some possibilities.

 

[rCadeGaming]

Signal is RGBS - (five wires, RGB + ground + sync).

Sorry to jump on you about that one.  It occurred to me later that you could have already meant RGBS or RGB+sync when you typed "RGB sync," and you already knew all that.  So, maybe it was just me being thick 

They are connected using a pre-built JAMMA harness that I've bought, which has a connector that plugs into the VGA board.

If the harness is wired to correctly to Jamma standard and the GBS is designed for a normal Jamma (which I would guess it is), there's probably no problem there.  You should look up the Jamma pinout and the GBS pinout to make sure everything's correct though.  You probably wouldn't be getting as good of a picture as you are if something's mixed up, but just one more thing you should rule out.

TV is a Samsung LCD, connecting via VGA input.
The VGA adapter's On Screen Display is stable though (while the rest of the picture jumps), so I don't think it's due to the TV itself.

Yeah, that makes that OSD confirms it's not the TV, but I'd plug it into a CRT monitor to be 100% sure.  What resolution are you running in?  I'd recommend using 640x480 and running it through an SLG3000 when you get it working.

I'm getting a (non NEO-GEO) JAMMA board to test whether the VGA card has the same problem or not.
Once it arrives I'll hopefully be able to rule out some possibilities.

Very good idea.  From your description, problems with the NEO GEO sounds like a possibility.

[newsdee]

The board did not arrive yet so been doing a number of other experiments.

I've redone many connections (soldering or crimping everything) and tried using both the PC PSU and a little 5V power supply I've found at a store (3.5A so seemingly plenty for my purpose).

First conclusion: the problem is way worse if I use two power supplies.
What could cause something like this? Maybe the grounds need to be connected?

Other than that, connecting everything (minus the -5V line) to the PC PSU seems to work very well.
The image has even less interference, but I haven't yet tried to run long on this config (I'll try that next).
Given the lack of -5V it doesn't seem like a long term option though.

[rCadeGaming]

I don't think you should be using two power supplies unless they are feeding separate things (+5, -5, 12) and they're well grounded.  Even then, Idk, sounds like a bad idea.

-5v is part of the jamma standard, but many boards don't actually use or need it.  I don't know about the NEO GEO specifically, you should ask other NEO GEO owners.

[newsdee]

I finally received the new JAMMA PCB - it's one of those multi game pcb that also features VGA out.

Connecting it to the GBS-8200 gives the same behavior as the MVS.
For example if I use the MVS and the screen starts to jump, then switch off and change PCBs, the effect is still happening when I power back on.

The new PCB has VGA out; using that instead of its JAMMA output works fine.

I read many forums (tried registering to neo-geo.com but doesn't seem to accept new users),
and I found mention here that the self heating of the board could cause issues: http://eab.abime.net/showthread.php?p=759262

I reduced the CLAMP SP and ST settings to 3 and 4. It seems to help and delay the start of "the shakes".
At least, now I can play for 30-45 minutes before noticing any effects. Not great but better than before.

Tried the PC power supply again (all the 5V going to it) and the image seems very stable with it.
I would rather not use this PSU though; so I'm going to keep trying with the arcade one.

So now I'm thinking the issue is from one of these:
- the sync signal of the MVS comes in too hot and heats the GBS circuits, triggering the problem.
- the power supply is not performing well, causing the heating of the GBS

I suppose next I should try using a variable resistor on the sync line.
And if that doesn't work, try to get an arcade power supply from a better brand...

[rCadeGaming]

Sorry about the NEO GEO forums, I didn't know that.

When I said the sync signal is too "hot" I didn't mean it was literally "hot" and that it was "heating up" the GBS.  I meant "too hot" as slang for too much voltage, in the case of a sync signal it's too much peak to peak voltage.  Sorry if I was unclear.  A sync signal probably wouldn't literally heat up the GBS, it's just that it's probably designed to work best with a certain level.  That thread you linked to seems to be talking about boards heating up due to the power supply voltage, which is believable.

Anyhow, I'd agree with your diagnosis, it's most likely either too much voltage on the sync lines or it's the power supply.

The fact the clamp settings affect things makes me lean toward the problem being the sync.  I wouldn't use a variable resistor because then you have worry about what range you need (min to max resistance).  Instead just pick up a pack of resistors from Radio Shack or somewhere similar.  You can get a pack of hundreds of them; everything from 1 ohm to 10 meg-ohm (10 million ohms), so you'll have everything you need.

Cut the sync wire midway, strip the two ends a little bit, and connect alligator clips to them.  This will make it easy to test different resistors very quickly, just clipping onto them.  Start small, like 10ohms, and move up slowly and see what happens.

Keep in mind that the sync could be too weak as well.  If the problem gets better as you add resistance, the sync voltage was too strong; if it gets worse, it was too weak.

If you can't get this thing working after playing with the sync and hooking it up to a quality power supply, I'd consider if it's defective.  You could ask someone who has a working GBS to borrow yours and see if it works in the same setup.

[newsdee]

If the sync voltage won't heat up the GSB, then it would rule out the sync being the cause.

The behavior is that things start fine then slowly degrade, and remain if I cycle (off/on) the power or change PCB.
If I "cold boot" (wait a while for it to cool down then power on) then it works fine again for a while.

That said perhaps the sync voltage changes during operation due to the power supply.

I'll try the resistors when I can get my hand on them. I live in Hong Kong, and surprisingly I'm having a hard time finding them.
There is a street that has all kind of electronics... but somehow none of the shops I asked had them (was armed with pictures and the chinese translation, so I suppose they understood).

I'd prefer a local shop so I can browse items and maybe find some unexpected parts,
but if nothing works I suppose I can always order online in Digikey or similar.

[rCadeGaming]

It doesn't necessarily rule out the sync.  It still seems most likely to me.

See if you can find a variety pack of resistors online.  If you have to use pots, get a 100ohm, a 1,000ohm, and a 10,000ohm.  While you're at it, putting a 100ohm on each color line is a great way to tweak the colors and make sure they're all equal.

[newsdee]

Finally got some resistors. Turns out there is a small shop hidden away on a side of the street.
(for those looking for components in Hong Kong, it's WECL at 201 Ap Liu Street in Sam Shui Po; components are on the second floor)
http://www.weclonline.com/eng/

And it turned out that, as resistor values increased, the worse the sync signal became.
The best sync I could get was when I removed all resistors.... so, I think the problem is that the sync signal becomes weaker over time.

Given the other PCB board had the same problem,
it looks like the culprit is the power supply. Not sure where I can get a reliable PSU with +5/-5 and 12V though.
Maybe if I get an old PC power supply instead it will work better (I think mine has no -5V, don't really need it for NEO GEO, but I'd like to be fully JAMMA compliant in my setup if I want to get another PCB later).

[lilshawn]

Finally got some resistors. Turns out there is a small shop hidden away on a side of the street.
(for those looking for components in Hong Kong, it's WECL at 201 Ap Liu Street in Sam Shui Po; components are on the second floor)

 

trouble finding electronic parts in hong kong?!?!?

heck, i can't find a single part in north america that i can't order off ebay from china and pay 1/10th the price.

local guy charges 5.95 for a single TDA8179

buy 20 off guy in china for $10 

[rCadeGaming]

digikey.com

[rCadeGaming]

And it turned out that, as resistor values increased, the worse the sync signal became.
The best sync I could get was when I removed all resistors.... so, I think the problem is that the sync signal becomes weaker over time.

Given the other PCB board had the same problem,
it looks like the culprit is the power supply. Not sure where I can get a reliable PSU with +5/-5 and 12V though.
Maybe if I get an old PC power supply instead it will work better (I think mine has no -5V, don't really need it for NEO GEO, but I'd like to be fully JAMMA compliant in my setup if I want to get another PCB later).

Good, so you've confirmed is that the sync level is too low.  I agree that you should experiment with different power supplies to see how that affects it, but you need to try amplifying the sync directly.  That may be all that's needed.

This circuit would probably work well:

http://www.gamesx.com/grafx/pce_rgb.jpg

If your color is already good, you don't need to amplify the RGB lines.  Just build the bottom right circuit to amplify the sync. 

Now their is no indication EXACTLY how much this amplifies the sync.  It may work perfectly as is, or you may want to adjust some of the resistors to match your specific application.  Is there someone here that is knowledgeable enough to calculate the exact amplification level of this circuit and recommend if any changes are needed?

[newsdee]

trouble finding electronic parts in hong kong?!?!?

Well you see, I wanted to find a shop where I could see/touch/compare the components instead of just buying online.

Now HK has this little street where all the electronic shops are supposed to be.
It's not just shops - you also get rows of stalls on the streets with a lot of little vendors selling pretty much anything, old and new.

The closest I found was an elderly couple selling components spread out on a table as if it was fresh fish.
But surprisingly enough they didn't have resistors (they had capacitors, diodes and other stuff, not sure why no resistors).

Later I did some online research and  found the opposite extreme...
a company that only sells resistors http://www.hkresistors.com/

Then I found out about WECL, and going there it was exactly what I wanted:
shelves of little drawers with all kind of components, at a very good price too.

By the way if any retrogamers are in the area, you can also go check out a retro game shop at the Golden Computer Centre (shop 50A/50B).
Picked up an AES NeoGeo controller from them.... unfortunately they didn't have MVS carts (only AES).

[newsdee]

Good, so you've confirmed is that the sync level is too low.

Yes. Actually I went a step further yesterday and connected the PC power supply in permanent configuration (redid many connections, soldered some bits, etc).
I'm running without -5V like this, so I've lost the sound, but at least the picture is super stable.

I suppose I need to find an ATX PSU that has -5V, but keeps the high amperage of the one I have (24A on 5V).
That way I'll be covered no matter how much the PCB and the GBS-8200 try to draw.

[rCadeGaming]

So, now you're running both the PCB and the GBS off of the PC power supply and everything works great reliably (except audio)?  Looks like you've isolated the power supply as the problem.  A decent arcade power supply would be a good option, they're cheap, reliable, and usually have an adjustment pot for the +5v rail, which can be useful for PCBs.

Check your average draw with a multimeter.  I doubt you'll need 24A.  I think +5V15A is common on arcade power supplies, which should be plent.

[lilshawn]

uhm... a PC power supply has -5v on them.

on the ATX power supply it's the white wire (position 18)

on a standard AT style PC supply it's white or yellow (P9 connector position 3)

[MonMotha]

The -5V wire has been deleted from the ATX standard and may not be present on newer supplies.  The newer supplies also tend to have most of their power capability on the 12V rail(s), rather than 5V like you'd generally want for JAMMA applications.  In other words, find an old ATX supply.

[newsdee]

A decent arcade power supply would be a good option, they're cheap, reliable, and usually have an adjustment pot for the +5v rail, which can be useful for PCBs.

I have exactly such a supply. In theory it has everything, and it was cheap, but I guess I got an indecent unit
http://www.arcadespareparts.com/arcade_parts/power_supplies_transformers/15a_power_supply/13121.html

Can I measure amperage with a multimeter?
I can get volts, but I thought to get actual draw one would have to use an oscilloscope?

The -5V wire has been deleted from the ATX standard and may not be present on newer supplies.

Right. I don't see -5V on the sticker of power outputs of my PC supply.
I would have preferred using an arcade PSU, but I'll see what I can find.

[rCadeGaming]

I don't know if your specific unit was bad or if that's a poor model altogether.  $10 seems just too cheap.  I'd look for one in that same style that has some good reviews.

You can measure amperage with a multimeter, but you need with a specific setting that some don't have.

[newsdee]

Actually I was being dense... the NEO GEO MVS does not use -5V!
When I remembered that... I checked my wiring and found the speaker had been disconnected.
Now it works great   Tempted to get a scanline generator though (it never ends...)

About the PSU price, mosty I see three options: no brand, Wei Ya (taiwanese company I think), and Happ Power Pro.
The Wei Ya isn't very pricery if you get it directly from China (I saw the same priced at $30 in a US online store)
Anyway for now, I'm good with my newer ATX supply. It wasn't being used anyway.

I think I'll put up another thread with a "knowledge base" on the GBS... to save time for others that may have similar issues with it.
(I saw too many "now I fixed" posts without any further explanations while researching this).

[rCadeGaming]

Sounds great.

I'd stick with the ATX if its working fine now, but bookmark a good arcade supply in case you get a PCB that requires -5v or is picky about the adjustment of +5v.  Look for some reviews on those you mentioned.  Happ stuff used to be great, but is hit and miss now.  It's possible that their supply comes from China as well.  I don't know about the Wei-Ya.

[lilshawn]

I think "chungwa" and "Chiun hwei"? and "wei-ya" make most of the supplies out there (branded under various other brands of course.)

makes them easy enough to fix cause they are basically all the same.

I think the happ is a wei-ya...but don't quote me.


much like anything else you get what you pay for. Something that is abnormally cheap is cheap for a reason. but don't run out and buy the most expensive either...markup is a ---smurfette---, and lots of companies will just markup arcade parts to gouge people.

[rCadeGaming]

Totally agree.  Obviously there are exceptions, but I think a good general rule for most products is that the best value lies around the center of the price curve.

[rCadeGaming]

should probably link to this thread in your new one, Dee.

[newsdee]

should probably link to this thread in your new one, Dee.

Done 

Epilogue: I bought an SLG-3000 and the scanlines are fantastic. They hide a few defects and somehow makes the colors better.
It's hard to explain; but now I can't play without them.
If anybody is on the fence about getting it, try MAME with HLSL. I did for my NEO GEO games and liked the difference.