Hi everyone! I am new here and learning electronics. I recently "fixed" my broken TV but I can't make the remote control work (funny right). I opened the remote with a lot of force and cleaned it up (it had quite a bit of sulfate? In the microchip contacts) I thought it was the IR but it apparently works "fine" as the multimeter shows, but when I press any button it does not light up, and when I give it 2 Volts via my power supply it lights up perfectly fine. The circuit has 3 resistors, a capacitor and according to the meter they work fine. The transistor that I believe is pnp, in diode mode gives 0.7 and 1 which I believe normal. I have no idea what the weird blue thing with 3 legs is but it has continuity with the middle leg and the negative terminal. Any ideas will be appreciated. Thank you

 

hi amin,
Welcome to AAC.
Point your remote at your mobile phone camera, in a darkened room, if the IR LED is emitting IR, it will be visible on the camera.
Lets know what you see.
E

 

hi amin,
Welcome to AAC.
Point your remote at your mobile phone camera, in a darkened room, if the IR LED is emitting IR, it will be visible on the camera.
Lets know what you see.
E

Yep. That was the first thing I did. Nothing. The only way of the IR turning on is by applying direct voltage to it. The problem aren't the batteries neither because I also used the power supply at 3 volts and it didn't work

 

OK,
That sulphate you cleaned off, was it grey in colour.?
BTW: that 3 legged blue thing is a crystal resonator ~ 4MHz.
E

 

What resistance do you measure between the terminals of the crystal?
It looks like a battery has leaked and that can leave conducting paths across the board which shouldn't be there.

 

OK,
That sulphate you cleaned off, was it grey in colour.?
BTW: that 3 legged blue thing is a crystal resonator ~ 4MHz.
E

Thank you for your help I didn't even know there was such a thing as a crystal resonator. It had a blue color, in Spanish we call the blue oxidation "sulfatado" it is usual in old alkaline batteries

 

If I am reading your image correctly, R4 and C2 are missing.???
The copper tracking is corroded, I would suggest a new remote is needed

 

I'd say that the battery acid has corroded the tracks and caused shorts.

 

What resistance do you measure between the terminals of the crystal?
It looks like a battery has leaked and that can leave conducting paths across the board which shouldn't be there.

Hi! There are roughly 0.40 M ohms between the legs but the measurements keeps going up (I don't know if that's normal) and you are right. The TV was not functional for more than 2 years so the controller was just sitting there. I cleaned the board with alcohol

 

Hi! There are roughly 0.40 M ohms between the legs but the measurements keeps going up (I don't know if that's normal) and you are right. The TV was not functional for more than 2 years so the controller was just sitting there. I cleaned the board with alcohol

OK.
Were R4 and C2 originally there (maybe fell off when you cleaned the board)?
Try cleaning the board with a soft brush, water, and a little detergent (washing up liquid, dish soap) and then give it a good long time to dry out (>24 hours) somewhere warm but not hotter than you can keep your hand on.

 

You can find universal remotes for $5 in the store and for next to nothing at garage sales. I wouldn't waste time on a malfunctioning remote.

 

If I am reading your image correctly, R4 and C2 are missing.???
The copper tracking is corroded, I would suggest a new remote is needed

View attachment 160942

From my limited experience in electronics repair sometimes manufacturers print the same circuit board for different products and sometimes not all components printed make it to the circuit (that has been my ecpexperie with Chinese products) . For an smd component to fall out it would need high heat, or is that not always the case?

 

Corrosion can reduce some components to a friable state, which can be washed/brushed off.