PSone screen flickering a bit - how to get it (100%) stable?

bacteria · Post by **bacteria** » Sat Apr 28, 2007 5:31 am

Hi guys,

Would appreciate your feedback and comments please!

Making a GBA portable with a larger screen (PSone) as I don't like the titchy screen you get with a GBA SP and the original GBA screen is too dark anyway. I thought it would be fun to make a larger console because GBA games would be far more fun playing them on a bigger screen!

Hooked up an old GBA transverter I bought a few years ago, took it apart, used the case on the open GBA (in pic) as it gave more space while hooking everything up. I wired the RGB wires to the chip on the transverter directly

Pin 2 = Red, Pin 3 = Green, Pin 4 = Blue.

I then wired these wires onto the PSone wires (slot 1) - red to pin 4, green to pin 5, blue to pin 6.

The Sync (pin 3 on the PSone) wire was soldered to the pin on the Transverter (4th pin on the reverse of the Transverter, shown with red dot); and the Ground (pin 7 on the PSone) was soldered to the last pin on the Transverter (shown with the blue dot). Found these by trial and error, not sure if these are the best connections, only what worked! I tried to look for connections on the chip itself for sync and ground to wire up to the PSone but couldn't make it work, so wired these to the pins designed to go to the PSone plug on the reverse of the Transverter board:

It would seem logical to wire from the Transverter chip ( CXA2075M ) to the PSone for the sync and ground, perhaps someone knows the answer? The coloured dots show the RGB wires soldered to them. Anyone know the logical pins to solder the Sync wire to and the Ground to on the chip, to connect to the PSone??

Result looks like this (playing Mario Ball):

Works nicely, far better than using composite (better colour control) and no colour bleeding - RGB is better! Ignore the video cable on the picture, I had previously linked the PSone to composite input, before I got RGB working!

QUESTION 1

Issue is this - there is a little flickering on the screen, minimal; but it would be nice to get rid flicker entirely as it would be hard on the eyes over a play session potentially.

Does anyone know how to eliminate the minimal flicker? The Transverter is set to PAL (NTFS just scrolls the screen). Can the flicker be reduced/eliminated by a transister or whatever; or is it inherent on the PSone screen? Would using one single thicker wire to connect from the PSone pin to the Transverter reduce flicker for each of the RBG wires? (I used the PSone cable, soldered it to a wire from an IDE cable lying about and soldered that to the wire soldered to the chip (wire too short!). Comments?

QUESTION 2

If I use 5 x AA batteries, rechargable, 2500 Nimh batteries, would this be enough to power both the PSone screen AND the Transverter (both use 7.5v).

The GBA needs 2 x AA batteries too to work, if I connected two of the 5 batteries used above for the PSone and Transverter to power the GBA too, would that draw too much power from the batteries? I would rather use less batteries if I can; and 2500 NiMH batteries (photo) have a lot of draw.

Comment please!

I got the pictures (apart from the one showing my rig) from various sites (including this one) after lots of Googling. Not sure where I got them all from, thanks to all concerned!

Kurt_ · Post by **Kurt_** » Sat Apr 28, 2007 8:51 am

Looks great! I think someone did this previously, in a vacuum formed case and everything, and it was sweet.
As for where the Csync and Ground wires go, Ground goes to any ground (Like pin 24 on that block diagram) and Csync goes to the Csync on the PS1 screen and a pin on the block diagram. Truthfully I don't know, if I had to guess it would be CVOUT (20) or COUT. I wouldn't be bad if they were wrong, as long as they aren't high voltage pins. (You may have already solved this problem on your own, by the looks of the pictures) If not, this is your flickering problem.

To eliminate flickering, it would help to add some decoupling capacitors on the voltage lines. As for thicker wires, your wires are much thicker than the ones I used going into RGB. Mine were very high gauge, something like 32 or 30ish. (Possibly 28)

I'm not sure what a decoupling capacitor would do on the RGB lines, but if you feel like it, try it out.

NiMH batteries are plenty to power both of those. Except I would be safe and go with 6 or them, unless you must have 5 for your design. The PSOne screen has 7805 regulators onboard for sound and such, and much lower than 7 volts and the sound will shut off and the screen will start to get all wavy.

But I think people here have used 5 NiMH with good results. 6 is just the safe route, if you have 1 more.

As for hooking them both up to the same set of batteries, I would go for a regulator.To minimize draw, use a switching regulator from TI.com (You can get free samples) If you go to the N64 forums, there is a free sample of a preassembled 7 to 3.3 volt switching regulator. This will prevent uneven battery drain.

bacteria · Post by **bacteria** » Sat Apr 28, 2007 9:29 am

Pleased to hear someone else did this before; I couldn't find a link, did a lot of searching, I would like to have a link if anyone has it please.

Just trying to be careful - normal AA batteries are 1.5v each, so 5 of these are 7.5v; whereas AA rechargables are 1.2v each, so 5 of them = 6v and 6 of them = 7.2v. So using 6 x AA rechargables is safe?? I don't want to damage my setup!

Could I trouble you for the link for the mentioned regulator?

"decoupling capacitors on the voltage lines" - what do you suggest I need please? (I can pop into Maplin and get some if you advise - are they the 220uf capacitors mentioned on a website? - I thought they were to give a brighter image - do they remove flicker too?

I am being careful because I don't have a lot of electrical knowledge, only common sense, and I do a lot of research. I only learnt how to solder properly the other day!!

I don't want to blow these boards - already blew my old GBA somehow, this is a replacement (thank goodness I didn't blow the Transverter - can't get a replacement for that!!).

Lots of work to do on this yet, a nice ongoing project!

All advice gratefully received!

Kurt_ · Post by **Kurt_** » Sat Apr 28, 2007 10:05 am

Anything over 9 volts is the setup damaging range for the PSOne screen. 6 AA's are fine.

Dkap's site seems to be expired, it may have moved, maybe someone else has a link to it.

DC/DC Step Down regulators:
http://focus.ti.com/docs/prod/folders/p ... ht233.html

They run off 7.2V just fine, apparently. Never used one myself. The topic is here: http://benheck.com/phpBB/viewtopic.php?t=7437

The decoupling capacitors are quite simly a capacitor set up in parallel with the voltage in (Battery pack +) and ground wires, to level out possible voltage spikes. Since the PSOne screen has unregulated video circuitry, this could help. It definitely couldn't hurt. Any value will work, but the repackaged PSOne screens (Zenith, etc.) has a 1000uf cap soldered to the 7.2V and Ground lines on on of the regulators.

DK · Post by DK » Sat Apr 28, 2007 10:08 am

http://portablesofdoom.org/portables.ph ... order=desc

Scroll down and theres one called "Nintendo Game Boy : Reaperman's GBA Somewhat Less Portable"

bacteria · Post by **bacteria** » Sat Apr 28, 2007 10:31 am

DK wrote:http://portablesofdoom.org/portables.ph ... order=desc

Scroll down and theres one called "Nintendo Game Boy : Reaperman's GBA Somewhat Less Portable"

Shows pic, but site is down.

At the moment, I am running my project off mains power (7.5v power supplies - official ones), so I presume the voltage is constant - thought I would try to get things working like this first before venturing onto battery power!

So are the decoupling capacitors therefore for connecting to the batteries (looks like this is what you mean?); or to each of the RGB wires? Is this what the 220uf capacitors are for, and would they help or hinder? Sorry, I am a noobie!

I believe I tried connecting the csync and ground wire to each of the remaining pins on the CXA chip, no luck; although I didn't try the ground on the PS output and just try the csync wire on the CXA chip (didn't try this combo - will try it in a couple of days). Just hope I don't blow anything.

I am using an official PSone screen.

Kurt_ · Post by **Kurt_** » Sat Apr 28, 2007 10:59 am

There is a simple circuit to boost RGB signals, but I doubt that is your problem. Buy a 1000uf capacitor and attach the positive end to your voltage in line (any spot that gives your 7.5V, really. As long as it isn't past a diode) and the negative end to ground. It should clear up your video.

bacteria · Post by **bacteria** » Sat Apr 28, 2007 11:09 am

Kurt_ wrote:There is a simple circuit to boost RGB signals, but I doubt that is your problem. Buy a 1000uf capacitor and attach the positive end to your voltage in line (any spot that gives your 7.5V, really. As long as it isn't past a diode) and the negative end to ground. It should clear up your video.

So does this mean attaching the positive end of the capacitor to the positive of the battery, and the negative capacitor end to the negative of the battery, in other words like an "H" shape, interconnecting?

battery + battery -
|aaaaaaaa|
|aaaaaaaa|
|aaaaaaaa|
|----cap-----|
|aaaaaaaa|
|aaaaaaaa|
>PSone >PSone
pin 1 pin 2
(+) (1)

Would this improve the picture quality for mains (7.5 converted) power and also for batteries, or just one of these options??

You are being most helpful, I appreciate your assistance!

Kurt_ · Post by **Kurt_** » Sat Apr 28, 2007 12:02 pm

That's basically how to do it, but if you do it in a place where the two lines are close together it will be less messy. Pin 1 and 2 are too close for my liking. Try something like this:

http://common.ziffdavisinternet.com/uti ... 095,00.jpg

Where the positive cap end is hooked up to the 7.5V pin (the one without the wire) and the negative lead is soldered to the ground strip (labeled PU3)

Or right at the battery. Your choice.

bacteria · Post by **bacteria** » Sat Apr 28, 2007 2:51 pm

Kurt_ wrote:That's basically how to do it, but if you do it in a place where the two lines are close together it will be less messy. Pin 1 and 2 are too close for my liking. Try something like this:

http://common.ziffdavisinternet.com/uti ... 095,00.jpg

Where the positive cap end is hooked up to the 7.5V pin (the one without the wire) and the negative lead is soldered to the ground strip (labeled PU3)

Or right at the battery. Your choice.

I have a wire already connected to this chip and to pin 12 (pin 10 on slot 1) so the PSone screen stays on. This was recommended on BenHeck to stop the screen going off.

You mention "Where the positive cap end is hooked up to the 7.5V pin (the one without the wire) and the negative lead is soldered to the ground strip (labeled PU3)" - is this still ok, given that I have a wire from the positive going to pin 10 on slot 1? (ok?)

I will put the capacitor on my shopping list! Oh, which way round on a capacitor is the positive end please??

Kurt_ · Post by **Kurt_** » Sat Apr 28, 2007 3:20 pm

In the picture, the pin with the wire should go to pin 12. I'm not sure what you mean by pin 10 on slot 1, because that is green in. You want 5 volts going to the last pin (12) on slot 1 to get the screen to stay on.

To hook up the capacitor, hook the positive end to the pin in the picture without the wire, and the negative end to the only remaining connection on the regulator. Unless another forum member suggests a better place. But like I said before, this is where the repackaged screens have one.

As for which is the negative side of the cap, usually it's the side with the big white stripe with negative signs on it.

If not that, it will have some sort of white stripe or marking in white to indicate it is the negative lead below it. (Sometimes it's not dead on below, but it is always the closest to it. Use common sense in this situation).

bacteria · Post by **bacteria** » Sat Apr 28, 2007 7:31 pm

Yeah, confused myself, I did mean I wired from the chip to pin 12!

Did a search on capacitors, Maplin is my local electronics store here in the UK. There are oodles of capacitors in all shapes and sizes. Which one do I use please?

http://www.maplin.co.uk/search.aspx?pct ... lasstype=M

If the capacitor is tiny I might solder to the chip directly (I presume below is what you meant); otherwise if it is bulky I will have to do it at the wires coming off the battery terminals as I will have far more space there to play with. Somehow I have to work out how to get the PSone screen and the GBA mobo (and controller wires connected) and the GBA Transverter all together without the end result being too bulky!

Here's another noobie question - on the GBA Transverter PSU there are 2 joined wires (naturally) going into the connector end for the mobo; the one with the white stripe is presumably the positive and the plain black one is the negative, right? I need to cut this wire to connect it to the PSone connections 1 and 2 for power, so the 6 x AA batteries supply power to both mobos. I just bought 12 x AA rechargable 2500 NiMH batteries off E-bay for about Â£6 ish, so this will help!

Thanks again for your continued support, Kurt_

Kurt_ · Post by **Kurt_** » Sun Apr 29, 2007 10:22 am

For a decoupling capacitor, the value really depends on the number and deviation of the spikes. From a battery, I don't see too many occuring, but you shouldn't go much higher than a 1000uf capacitor. The higher, the more it will filter out, but the bigger it gets, and possibly some other things. Try for around 500-1000uf, maybe 1200. They are relatively small, no thicker than a AAA battery and maybe half its height.

I completely forgot. You want a voltage of around 1-3 volts higher than your lines. So an 8-12V, 500-1000uf cap.

I'm looking on the maplin site but it's all very disorganized. The kind of cap should be an electrolytic, but I don't think it matter a hell of a lot.

Also, that picture isn't working.

If you don't find anything on maplin, try ebay:

http://cgi.ebay.co.uk/Capacitor-1000uF- ... dZViewItem
Long ebay search link

10V seems to be the standard. Note the side showing in the picture has a a yellow stripe with negative signs (rectangles) down one side.

bacteria · Post by **bacteria** » Sun Apr 29, 2007 1:50 pm

Kurt_ Thanks again for your assistance. Based on your recommendation I have just bought (and paid for) one of these capacitors from the direct link you provided. Hopefully it will arrive in the next days!

Given the size of these things I will have to do the "H" configuration (ie at the battery terminal ends) as it is clearly too big to attach to the chip, as I intend to mount the two other boards behind the PSone mobo (GBA mobo and GBA Transverter mobo). I will use some rubber type foam (or similar) to keep the boards apart.

If this capacitor makes no difference (to elimiate the minor flicker), any other ideas please?

Kurt_ · Post by **Kurt_** » Sun Apr 29, 2007 2:41 pm

I have a good feeling it will. Are you still running it off wall power or using the batteries?