Nintendo Vs system sync issues

[SNESNESCUBE64]

Hi Atariage! I am new to the forum but I heard a lot of great things about here, and I figured you guys could potentially help me with a problem I am having with my Nintendo Vs System (If this is in the wrong section I apologize in adavance).

 

Anyway, I went to go test it today as I finally got a jamma adapter in the mail on my VGA monitor, and the picture is flickering as if it has a sync issue. Now I am converting from the RGB with a GBS-8220 as I do not have an actual monitor for it (am building this cab from the ground up with just a board). I linked a video down below to show what I am talking about. Do you guys have any suggestions on how I can fix the sync issue? I do realize that the color is off, it has the wrong ppu version of the ppu in.

 

 

https://www.youtube.com/watch?v=ZQ4YBRxpBvw

 

 

 

[SignGuy81]

I think the board has a lot of caps. Do you have an ESR meter? If not do any of the caps look bulged or is there any leakage around any of them?

[SNESNESCUBE64]

I just fixed it! It turns out it was a power supply problem.

 

How it works: So basically, the converter uses the -5V line to un-invert the colors (Nintendo unisystem boards output inverted colors because of the sanyo monitors). So what was happening is my power supply is outputting -4.4V instead of -5V which is too high. So what was happening is that the sync was also at too high of a voltage causing it to have a different sync than what is needed.

 

My solution: I put a potentiometer on the sync line which allows me to adjust for this higher-than-necessary voltage. So far, it seems to have worked. There are still little blips here and there, but I am going on a limb and am gonna say that it just needs more fine tuning.

 

Thanks for the suggestion SignGuy81, all the caps on the board are fine, this is the first thing I checked. To be fair, re-capping it is probably my worst nightmare. I counted and there are more than 60 electrolytic caps and about as many ceramic ones.

[SignGuy81]

When referring to voltages in elecronics we would not say that -4.4V is higher voltage than -5V even though it is a higher number. The only thing that gives a voltage a negative polarity is because the positive was tied to common ground but it is still 5V of force no matter where the negative or positive is connected with respect to ground. If it was a typo and you meant a number different than -4.4V which would be too low a voltage, I understand, but either way I would fix the power supply issue before any other to get it right.

[SNESNESCUBE64]

When referring to voltages in elecronics we would not say that -4.4V is higher voltage than -5V even though it is a higher number. The only thing that gives a voltage a negative polarity is because the positive was tied to common ground but it is still 5V of force no matter where the negative or positive is connected with respect to ground. If it was a typo and you meant a number different than -4.4V which would be too low a voltage, I understand, but either way I would fix the power supply issue before any other to get it right.

Yeah, I plan on buying a different power supply. I learned my lesson on buying a cheap power supply. I think I am going to modify a PC Power supply as I have a verified good working one on hand.

 

Thanks for the correction, I am new to this sort of thing, I have never used negative voltages before. I'm just glad it's working at this point, I was getting stressed out about it.

[SignGuy81]

Yeah, I plan on buying a different power supply. I learned my lesson on buying a cheap power supply. I think I am going to modify a PC Power supply as I have a verified good working one on hand.

 

Thanks for the correction, I am new to this sort of thing, I have never used negative voltages before. I'm just glad it's working at this point, I was getting stressed out about it.

 

NP, glad I could help out.

 

Easiest way too explain though I didn't think of earlier is to say for example you have a dual supply, +5V, and -5V, and a common ground. Say you have 2 leds and some resistors, one to monitor the +5V and the other the -5V.

 

With one LED you tie the cathode to common, and the anode to a resistor then to +5V.

 

The other LED you tie the anode to common, then the cathode to a resistor then to -5V.

 

Well, if the -5V supply went unexpectedly lets just say for example to -15V and the LED burn out, we wouldn't say it burnt up from too low a voltage. It would actually burn up from too high current but you get what I mean though.

 

EDIT:

I should have clarified something above and said resistors figured up for max current with a 5V supply but I didn't mention that and didn't put a figure in because it can vary. You could still say the LED burnt up because the supply voltage was too high, but not because too high voltage across the LED as it would have been too high current as the voltage drop across the LED would be the same as the normal voltage drop, as the rest of the voltage would drop across the resistor. I probably should have just used bulbs for the example.

Edited February 28, 2018 by SignGuy81

[SNESNESCUBE64]

It seems this is a really bad power supply, the voltages keep on fluctuating and I can't imagine that it's a good thing in the long-run. Any recommendations or should I just get a good PC power supply and use that?

Edited February 28, 2018 by SNESNESCUBE64

[SignGuy81]

It seems this is a really bad power supply, the voltages keep on fluctuating and I can't imagine that it's a good thing in the long-run. Any recommendations or should I just get a good PC power supply and use that?

 

I think your PC supply idea is great.