SNES Jr black screen and not working

I've got a pristine snes jr and it works fine. I unplug power, av composite cable, controller, and game then plug those same things in this so-so looking snes jr and I get nothing. Screen doesn't flicker and I just get the black screen. I've never tried repairing an electronic board but here is the troubleshooting I've done so far with what I know.

I opened up the so-so looking one and the metal around pin game connector is starting to look rough with pitting but the pins look okay. I haven't tried to clean the pins yet because not sure what would be the best way. I used a voltmeter and discovered my powersupply puts out 9.5v and not 10v but it runs the other snes jr no problem. I tested the pins on the bottom where the power jack is connected and I'm getting 9.5v there. On the top of the board in the top left corner before the game connector I saw a circle with a +/- labeled TC1[SNNM] and I'm getting 3.36v there but no clue what its supposed to be. I also test the continuity of the rusty switch and I get continuity with it on and none with it off so that seems like its working. The capacitors look fine but not sure what/how to test those using the pins on the bottom. The worst looking things on the board is the metal around the game connector and rusty switch. If those 2 items were replaced it would look really good!

Any suggestions on what I can try?!?!?!?!?!? I want to get this one going and try to RGB mod it which will be my first for a snes jr.

 

sorry to hear this but you ic u1 chip is dead.

 

You can't diagnose that from what's been said.

It could easily be a few other parts

 

I'm all for testing and trying different things but need some guidance

 

Check the 7805 output voltage, if it's 5v then check cartridge connector, clean it if needed. If voltage is below 5v, then replace 7805, if it doesn't help, then probably you have a short somewhere or dead chip, if there's more than 5v (7+ volts) on 7805 output pin then it will be better to keep that PCB for spare parts - more than one chip will be fried in that case.

 

After searching around the 7805 is the regulator on the heat sink and one side should be putting out around 5v and other around 9v, right? I'll check that tonight.

 

Yeah.. That last picture you posted shows it. You should have 5v on the far right leg.

 

I get .1v on one side and nothing on the other. Wonder what the % chance a new one will fix it but where can I get a replacement for a fair/decent price?

 

Have you checked the fuse in the console, just near the power socket?

 

I don't see a fuse and don't think the snes jr has one.

 

Mine does, its surface mount. Labelled F1 on the board, just behind the power socket

 

I don't see a removable fuse

 

Never said it was removable.

 

Would be nice if it was

My interpreation is you add a fuse to electrically protect something or system from over amperage so I would think it would be removable. I've only dealt with removable ones like in my car, back of the car radio, battery chargers, and so on. So odd to me they have a fuse soldered on.

I tested the continuity across the little thing at F1 and shows good.

 

Cars are supposed to be user serviceable. Most electronics arent

So its not the fuse at least.

Do you get 10~ volts on one of the legs of the voltage regulator?

Even if its broken, power should be getting to it.

 

The 7805 regulator I get get .1v on one side and nothing on the other. Going to order one, replace it, then see how it does.

 

Well then the fault sounds BEFORE the regulator. One side is input, which if its not getting power - it wont work.

You should measure for voltage, then try 1 side of the fuse and then the other and basically work your way down from there (should go to the switch, then back up to the regulator) and find out where the voltage stops.

 

Check that F1 thing, looks like a fuse to me.

 

Been over that already

 

I started from the beginning and well I got the 9v coming in to the regulator and 5v going out after I turned the console on! I took an old sock and cut it up to clean the game contacts. I used isopropyl alcohol to soak the material and a thin piece of plastic to wedge the material in and out. The snes works now but 80% of the time it will not boot up. I think cleaning the contacts helped but I think something is up with the switch.

Switch On and console working the switch reads .25v
Switch Off it reads 8.6v
switch on and console not working it reads .05v and screen is dark dark green and grainy or just plain black

when it doesn't boot with the switch on, the regulator is working as it should