MVS supergun picture trouble

[malebolgia]

I have a problem with my mvs supergun as well as with my AES. Both display really clear, sharp and colorful pictures on my tv using an rgb cable, but there are lines flashing on screen that look like graphics glitches. This problem is absent on another tv of mine. The tv that has this problem seems to be RGB compatible since my megadrive works fine on it using the exact same rgb cable, also on 60 HZ setting using a 50/60 hz switch I built in. When I opened up the tv there were RGB controls as well as a LOPT as found in arcade cabinets (with screen and focus knobs), so it seems obvious to me it is an rgb compatible tv as well as 60 hz. Like I said, the picture is very good apart from the problem mentioned. Does anyone know if the rgb output from MVS/AES is markedly different from the megadrive's? When I connected a capcom cps-2 board to my supergun, it had the same problem by the way.

I live in Europe by the way, so it is essentially a PAL tv.

 

[MKL]

Try wiggling a bit the connector in the scart socket and see if it has any effect on the picture. You see, RGB is tops as a signal but the scart connector (on both cable and TV) has a real bad design (the French, who created it, should stick to croissants and soufflés and leave electronics alone ), especially if the scart socket on the TV is placed horizontally (vertical is the way to go, as in recent Sony TVs) because the weight of the cable puts a lot of stress on the pins of the socket. I have an old TV that shows similar and worse problems (sometimes the blue goes away altogether!) because of this reason. Perhaps it's the same with your TV...

 

[malebolgia]

Thanks for the reply. I've tried that extensively and it doesn't help. Also, with my sega megadrive it works perfectly, so the connection shouldn't be the problem. Isn't there something about the rgb output of mvs/aes that's markedly different from the megadrive's? It's so weird cuz if my set either doesn't support RGB or 60 hz there shouldn't be a color picture at all, right?

 

[MKL]

Alternatively I was thinking of RFI/EMI problems with equipment hooked up to that TV but if you say the Megadrive works fine and with the same scart cable, that cannot be the case. The RGB/60Hz can also be safely ruled out. The RGB output of an arcade board (that includes MVS) is different from that of a console (that includes AES) in that it is usually stronger, which results in an overly bright picture (that's why you often find RGB pots on superguns) but this does not concern AES and in any case it would never give the problems you're experiencing. If it were an MVS-only issue I'd advise you to check the voltage which could be too low and thus give such problems but if it's only on that TV and also happens with AES (but not MD!), I don't know what to tell you...do you have any other arcade boards to test?

 

[malebolgia]

yeah, I have 3 cps-2 boards which have the same problem on this tv set, but again, not on any other.

 

[MKL]

sorry double post

 

[malebolgia]

in short, only the supergun (regardless of which board's being used) and the aes have this problem. Could it be that i should add a resistor to the +5v on the supergun's rgb out? But that wouldn't explain the aes problem would it?

 

[malebolgia]

here's a picture of what these flashing stripes look like:

Sometimes the number 'S100' is discernible among the 'glitches'.

weird huh?

 

[MKL]

in short, only the supergun (regardless of which board's being used) and the aes have this problem. Could it be that i should add a resistor to the +5v on the supergun's rgb out? But that wouldn't explain the aes problem would it?

well, the resistor (100 ohm) on the +5v line that goes to scart pin 16 is necessary because you need a voltage lower than 5v on scart pin 16 (it must be between 1 and 3V), but this cannot have to do with your problems (VCC to pin scart pin 16 is for RGB switching and your TV is displaying an RGB picture already).

On a side note, the AES outputs 5V from the A/V port, so the resistor should be inserted in the cable. And if you want to use that cable also with the supergun, you shouldn't put the 100 ohm resistor in the supergun, or else the total resistence will be doubled...

 

[malebolgia]

so the aes and mvs output 5v each? What about the MD? cuz if that's different it might be the problem after all...

 

[malebolgia]

it's an old tv, perhaps the 5v is just too much?

 

[MKL]

What's odd is that the lines show up only on that TV and only with AES/MVS/CPS and not other consoles...

 

[malebolgia]

yeah. So the only difference I can think of is the voltage output (IF the MD's is 3volts...) and the age of the different TV's I've tried it on.

Do you know if the MD's output is 5v?

 

[MKL]

so the aes and mvs output 5v each? What about the MD? cuz if that's different it might be the problem after all...

It's the supergun that may or may not have a resistor in the 5v pin of the A/V port: I don't know whether the resistor (if any) is in the supergun or in the video cable: you can check that with a multimeter.

it's an old tv, perhaps the 5v is just too much?

Do you know for sure the TV is getting 5v (i.e. no resistor)?
In any case as I told you I don't think that could be the cause of the problem. I've tried myself 5v (without resistor) on scart pin 16 of a 15-year-old TV and everything was OK (the higher voltage could cause problems in the long run).

 

[malebolgia]

I know for sure that the supergun out hasn't got a resistor on the 5v cuz I built it myself.

 

[malebolgia]

...and it isn't in the cable either...Just checked it to make sure...

 

[MKL]

And there's no resistor in the cable either? If so, I'd recommend to put one.

As for the MD, I don't have one to check atm but I'm pretty sure it's the same as the AES (i.e. output = 5v): the 1-3V is a scart (read European) specification the Japanese console manufacturers didn't bother about...

 

[malebolgia]

..but my MD is a european one. Wouldn't sega europe have added a resistor to the rgb out then?

 

[MKL]

..but my MD is a european one. Wouldn't sega europe have added a resistor to the rgb out then?

Nah, I'm pretty sure they never did that on any console...a PAL AES I've seen did output 5v from the A/V port.

But you can check that easily: open the MD and measure the resistance between the pin on the A/V port and the VCC pin of some ICs...

 

[malebolgia]

But this probably isn't the problem at all, right? It's really weird...........

 

[RVF400]

i got a funny problem with rgb on my pal tv too, i recently built my own RGB cable for my saturn, yet it displayed composite, i bought a PROPER RGB cable and it worked fine, when i opened them both up i compared them, the one i made didn't have a resistor on the red line, that was the only difference, now my tv works fine with RGB and 60hz but it kinda displays a ZOOMED IN image, i don't know why, im missing parts of the screen its really anoying any1 know why?, how cani adjust it, theres nothing on my remote!.