I feel ashamed to admit that I accidentally reversed the polarity of the power going into my official PSOne screen and burned up the two fuses. I feel even more ashamed to admit that I stupidly jumped the two fuses.

My experience in electronics should have told me why the screen was not powering on, but I was greedy and WANTED the screen to power on so I kept on going. I was using 5 alkaline AA batteries taped together to try to power the screen, but I should have known better. I connected the power and I saw the backlight flash. I figured that the batteries could not handle the current, but I tried it a few more times. Connected....Flash....reconnected....flash....reconnected......NOTHING.....wtf....reconnected....NOTHING!

I have killed my one and only PSone screen. I measured the voltage going into the screen from the batteries. As soon as I connect it, it drops from ~7.5V to 0V suggesting that there is a massive short somewhere. I'm hoping I fudged up the 7805 voltage regulators and that I can just replace them.

Is there any hope left? I guess I ordered replacement fuses for nothing.

7805s have polarity protection built in, but there's one chip on the PCB that runs straight off 7.5v - the video decoder. If you swapped the polarity, you probably killed this chip. Sell the LCD by itself, or keep it in case you crack your next LCD.

After the incident where I switched the polarity and blew the fuses, I jumped the PS1 fuse and was able to see the screen brightness and volume bars on the screen so at least that part was working, but the backlight did not work and I could not see the video from my sega genesis or hear any audio. Since the bars were showing on the screen, does that mean the video chip was working? Now that it is completely burned out, it does not make any noise out of the speakers or make the screen slightly darker when power is applied. Theres a major short somewhere, but the weird thing is that I have not seen any smoke or smelled anything burning.

I'm going to try to desolder the larger components and test them one by one.

It would be great if I had a thermal imaging camera so I could see what parts of the circuit were getting hot first, indicating a high current. Could that possibly work for troubleshooting?

Don't worry about desoldering. If you see your green bars, that means most of it is working. You should at least hear audio. If not, you aren't hooking it up right. I'm not sure how much the decoder is involved in the OSD volume bars.

That was before the backlight flashing incident i described in my first post. Now the circuitry does not turn on at all so I cant test the volume and brightness controls.

Woohoo! There is hope after all!

I desoldered the transformer for the backlight and the major short that was causing the voltage to go to 0 across the input disappeared!

I can see the volume and brighness on screen controls again!

Now I need to plug in a video and audio source

Oh, and this time I went with 5 "D" cells instead of the 5 "AA"s I had before just to make sure they could handle the current demands.

Wish me luck! I'll report back in a bit.

6 cells (rechargables) will give a max of about 8.5v on a freshly charged set, 7.5v when they have been left about for a while. If however you are using alcaline cells, then yes, 5 cells should be ok (about 7.5v) as 6 cells might blow the fuse in the PSone screen if you are unlucky (if 9v or thereabouts). If you use 5 rechargables, they won't power the screen for very long; once the cells get under about 7.2v the PSone screen doesn't work.

You can use AA cells if you are just using them to power the PSone screen (eg test building), I am doing this at the moment on my project (6 x AA's).

Does that mean I cant use tje 7.2V InfoLithium 4000mAh battery I had in mind?

I have GOOD NEWS though! It was the backlight that was FUBAR'd and causing the short. I removed the transformer and the screen is working perfectly now I had to use a flashlight but everything seems to be OK. The sound works too

And just for reference, I did some testing and found that, without backlight, the screen uses around 180mA without the sound connected to it (might be possible to get it lower if the sound chips are removed). With a sound input connected, the screen peaked at 260mA (I only had 1 speaker connected though so it might be slightly higher with both speakers connected).

Sorry, error - 7.2v is fine, of course, the figure when the screen dies is a bit under 7v; anyway, yes your cell is fine.