Psone LCD conversion, final revision.

I’ve had one of these kicking around and fed it composite video as a test monitor for some time, but it’s always been in a sort of unfinished and dangling state. Today I buttoned it all up so it can just be another piece of test equipment.

To get this screen to do what I want there are a couple things I had to do. First was permanently connecting 5v sense in so that the screen powered up:

5v-sense permanently pulled high

Next I had to deal with the sound. I was not hearing anything. Years ago I had tied the headphone switch wire to ground, that did not work and was not what was recommended by the mod guides anyway. Next I followed the mod guides and tied the headphone and headphone switch wires all together. This did not work either. I resorted to checking the lm4835 datasheet and found that the way to permanently set the headphones to disused was to tie the HP Sense line low. I did that and the speakers jumped to life.

I removed a series resistor and injected my signal to that pin.

The next issue was this LED mod I had done years prior. I must have broken the backlight and done this mod when I had much less soldering skill and equipment at hand. I also followed the advice on where to place things which I don’t think was optimal. The circuit is basically three white LEDs in parallel all connected to a single 10R current limiting resistor and that’s connected to 5v. That’s about 56ma per LED. I don’t really believe that but it’s working so I cleaned up the wore routing and soldering and just put it back. Originally the resistor was hot glued to the strip of black electrical tape under the LCD in the center. The problem is there’s a plastic post there so I relocated it to the side of the LCD in the nice open space (and heatshrunk it for more secure insulation).

All that done the screen still had a strange blown out look and I remembered that there is a ‘brightness mod’ that was mentioned. I had done that and now don’t really like the consequences. Once that jumper was removed it looked a lot better.

You can see the solder joints that I removed a jumper from. That mod looked bad.

The next issue is that the composite and RGB inputs take different audio inputs. Theoretically I could have kept hacking on the amp circuit and injected audio straight into there and ignored the switching circuitry that exists based on which input gets a lock. Instead I just used a double pole double throw switch to use one set of inputs for both modes.

The final issue you can see fixed above. I hate that this takes 7.5v in. It may just feed a couple 7805 regulators but I don’t really want to chance it so I added a regulator so I could comfortably feed it with 12v and not have to worry.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: