PSone screen audio amp causing screen blurbs...

G-force · Post by **G-force** » Wed Feb 08, 2006 5:03 pm

The screen looks fine until there is any sound. Then it gets all wavy and distorted. The louder the sound, the more it gets distorted. No sound, no distortion at all.

I'm thinking it's a problem with the power supply. I'm using a 9.6V (2000 mah) battery. I removed and replaced the 7805s with a 5V DC-DC converter from ti.com for more efficiency. For the 7.5V line I used a 8V DC-DC converter from ti.com. Even though it says on the data sheet it requires a 12V input, I got 8V from it with my 9.6V battery. I thought that might have been the problem so I replaced it with a 7.5V regulator. I still got the same results.

Any ideas?

superdeformed · Post by **superdeformed** » Wed Feb 08, 2006 5:10 pm

Did you measure the voltage on the 8V DC-DC converter with the screen turned on and the volume turned up? Usually for things like that, it will read at the right voltage with no load, but as soon as there is enough current going through them they start acting really screwy if you don't have a high enough input voltage. Is the minimum input for the 7.5V regulator the same, or is it not a DC-DC converter? Also, what's the current rating on the 5V regulators?

Kurt_ · Post by **Kurt_** » Wed Feb 08, 2006 5:44 pm

It sounds like a current issue for sure. Try hooking some regulators in parallel, or get some that can handle a higher current load.

G-force · Post by **G-force** » Thu Feb 09, 2006 4:20 pm

Both the 8V DC-DC converter and the 7.5V regulator were rated for 2 amps, more than enough to power the screen. I checked the voltage for a drop on both the converter and also the regulator, both stayed within operating voltage (7.89V and 7.38V) no matter how loud I put the volume.

I even tried splicing into the battery pack to get 7.2V and run the 7.5V line off that. I still got the same distortion. That only leaves the 5V line, with the DC-DC converter in place of the 7805s. But the DC-DC converter is rated for up to 2 amps AND when I check voltage while the screen/speakers are running I get 5V, perfect! There is no reason for it to not work!

Here is the page for the 5V and 8V DC-DC converter I'm using.

Could it be some kind of weird interference problem from the DC-DC converter? I'm really stumped.

SNESguy · Post by **SNESguy** » Thu Feb 09, 2006 5:38 pm

THis problem happened to me when I tried using some slightly larger Sony speakers with the PSOne screen. However, the speakers were a higher wattage, and therefore caused the screen to "thump" to the music.

Turns out the audio amp is very weak on the PSOne screen.

Are your speakers the factory ones or some different ones?

Try this: plug headphones into the jack and see if the screen still thumps. If it doesn't, then something's wrong with your speakers.

Then remove the speakers completely. If it still thumps, something is wrong with the amp.

Best Regards,

SNESguy

G-force · Post by **G-force** » Fri Feb 10, 2006 5:27 pm

Thanks for the idea, but it's not the speakers. They're the same ones that came with it, and they worked fine last time I used the screen.

Good news though, I found out what the problem was. The 5V DC-DC converter. Even though it was outputting 5V perfectly, it was still causing the screen distortion. I know this because I replaced it with a plain old 7805, and the screen ran perfect.
I woul still like to get the DC-DC converter to work though, since it has better efficiency than plain old regulators.

On the data sheet it says that a 1 uf (microfarad) ceramic capacitor is optional. But in this case I think it might be needed. Problem is, I don't have a 1uf ceramic cap! I looked through all my spare elctronic boards, PC monitor, VCR, alarm clock, everything. The closest I found was a .1 uf ceramic cap (has "104" printed on it which translates to .1 uf).

Anybody got a 1 uf (or even higher) ceramic capacitor lying around that they could spare? Pleeeeaaaase?

superdeformed · Post by **superdeformed** » Fri Feb 10, 2006 9:05 pm

A metal film capacitor will probably work too (such as this http://www.radioshack.com/product/index ... age=family ). I take it you do have a 100uF capacitor on the output of the converter?

G-force · Post by **G-force** » Fri Feb 10, 2006 9:22 pm

Thanks, I'll try that

Since I'm using two converters, would that mean I should put two of them in parralel to get 2.0 uf?
Yeah I have the 100 uf cap on each converter. I even went to such lengths as to try different 100uf caps, thinking that maybe the first one was broken or something. And I think a 16V rating on the caps is fine for a 5V and 8V output, right?

segasonicfan · Post by **segasonicfan** » Sun Feb 12, 2006 8:45 pm

wow I guess nobody reads anything I post >_<

I COMPLETELY solved this problem and it took me many long hours to do it. I've been asking people to put this in the sticky but no one listens to me

http://benheck.com/phpBB/viewtopic.php?t=8195

The problem is power spikes in the ground. You have to cut around the amp until ALL the ground are completely seperated. Plug the screen in and use a multimeter to test the negative voltage around the amp to make sure you've completely seperated it. This is a 100% fix, I used it for my PSTow portable :]

-Segasonicfan

G-force · Post by **G-force** » Sun Feb 12, 2006 9:05 pm

I read it! I thought of trying that too, but I knew that the screen worked fine before I used the DC-DC converter setup. Using a 7805 I was able to get it to work normally again. The whole thing is a problem with the 5V DC-DC converter (which I would like to fix, for more battery life)
And this distortion is not like what you were describing. This was so bad, half volume you could barely make out the screen among the tons of lines (that was only when there was sound though. If it was quiet it didn't matter how loud the speakers were)

I'll add that to the sticky too. Should have been done a while ago, I guess it just slipped through the net.