TV remote got wet. Still works but w/ very reduced range.

[Ed.Kloonk]

Patient presented is the remote control for a 10 year old 40" (wonderfully not smart!) TV.

Brand is Changhong or something. Rain water infiltrated remote for perhaps 24 hours. And sat that way for over a week before being looked at.

Has been opened up, dried and had 2 AA batts replenished. Now only works between 0 and 30cm from receiver on TV. Tried removing power to TV in case it just needed a reset.

Board appears ok upon visual inspection under natural light and naked eye. Control chip is at the bottom of the board ie the opposite end of the IR LED. I forgot to note the markings on the chip before clipping the case back together. But can re-look. Not exactly armed to the teeth with a lot of tools or test gear. 

Owner is fond of the TV.

Want to know:

if there is anything else I can do or check.
if the likelihood of successful repair is low or a waste of time.
if those learning remotes still exist. (Only need Power, Source and Volume)

[sleemanj]

The IR leds are driven at high (for an LED, maybe 100mA+) currents to get range, wouldn't take much corrosion resistance to cause a problem.

I would start by inspecting and cleaning battery contacts, maybe clean the led of course.  That's likely all there is to the whole thing really, led and control chip so there's not much else to do unless there is a discrete transistor driving the led.  Current for led drive won't go through the buttons or anything so they don't matter here.

Learning remotes can be easily purchased and since yours is still functional at short distances, you could do that.  (kmart has one for 10 bucks in NZ I assume about the same in au)

[PKTKS]

Yes i had a similar issue way back in the 90s..  juice spilled on remote..

After cleaning the device was poorly function...   


The oscillator was out of proper freq by just a small value..   check w scope the proper frequency...

Paul

[m3vuv]

not the issue i know but cleaning the inside of the ir rx window on the tv may help as well as its more than possibly dust covered!

[Ed.Kloonk]

not the issue i know but cleaning the inside of the ir rx window on the tv may help as well as its more than possibly dust covered!

Forgot to mention I did that when I was rebooting the TV. Yeah. I wish that is all the problem is.

[SeanB]

Scrubbed the entire board, and checked for any cracked solder joints? You can also replace the little electrolytic capacitor in there, normally I use whatever tantalum chip I can find that has a rating over 5V, and typically those are 47 to 100uF, which still allows the case to close. Check with your phone the IR LED is providing light, probably best done by pointing at a mirror on a far wall, and seeing if the brightness is comparable to the output of a similar remote transmitter. Transplant the LED from a dead or surplus remote into the weak one, as the IR LED's do degrade, and moisture wicking up the interface to the leads can cause issues.

Otherwise Chinese shop, and get universal remote, and program it, normally by putting into find mode and holding down power button till TV turns off for a lot of those remote replacements. Under $5 for the remote that can emulate 5 meeeelllion TV sets and other electronics, and then remove batteries from original for when you need the function buttons.

[tooki]

The IR leds are driven at high (for an LED, maybe 100mA+) currents to get range, wouldn't take much corrosion resistance to cause a problem.

1-1.5A (yes, whole amps), actually!! (The only reason they don’t incinerate on the spot is because of the low duty cycle and limited duration of use.)

[Ed.Kloonk]

Update.

Original remote control still functions the same, with very reduced tx range.

Found a universal remote on eBay for $20. Basic buttons work, advanced buttons didn't work. Tried a few model no. suggestions in the manual. Prolly better with just the basics anyway since it prevents accidental settings tweaking.

Owner is happy. I'm happy that I don't have to introduce a new, unwanted 'smart' TV into the mix.

Next visit I will remove batteries from old remote and write on the back 'reduced Tx range' and put in storage in case the need to go into settings is required.

If circumstances were different, I may have been able to fix it. But thanks to those that tried to help. 

As an aside, I found this video where the guy converts 2AAA to Lithium/USB. Don't know whether I should be impressed or horrified. What do you think?

[MathWizard]

Wow I didn't know those IR LED's were driven like that. For years I've wanted to play around with a remote control, but just never got around to it again. Now it might make some sense. I want to try some home automation stuff with arduino this year.

[Haenk]

Conversion to "rechargable" with an USB port sticking out?
What a nonsense.
Buy two AAA LSD cells, like Eneloops, and you are good for many months. I don't remember the date when I last changed batteries on a remote. TV is still working on the first set, Amplifier/CD (even though it has a nifty LCD) at least 2 years ago.
The battery changing is an absolute non-issue. IMHO.

 

[andy3055]

Sometimes you can buy a working remote of the same model on eBay. Recently I got a remote for an old camcorder for just 5 bucks. You will have to search with the model number of the remote and the model number of the TV of course. Mostly from people who had broken TVs.

[tooki]

Wow I didn't know those IR LED's were driven like that. For years I've wanted to play around with a remote control, but just never got around to it again. Now it might make some sense. I want to try some home automation stuff with arduino this year.

For what it’s worth, Vishay (most likely the largest maker of IR receiver modules) has tons of documentation about every aspect of IR remote control transmitter and receiver design. (And of other modulated IR applications like presence detection, photointerrupters, etc.)

[arjen]

Why don't you just buy a new one?

[hneve]

I'm sorry to hear that. It must be bothering you. You can try a digital remote if you can't repair the remote control. I have a universal TV remote app on my phone, which I downloaded from the App Store. It transforms your phone into a digital remote and is compatible with most popular TV brands. I use it when I am too lazy to look for the remote.

[rsjsouza]

I don't know which remote you have, but most IR remote controls use a PCB made of phenolic material. This material can acummulate water/humidity that could potentially degrade the performance of the circuit. This plagued amplifiers, receivers and all sorts of vintage equipment that "went under water".

Drying the board with a moderately warm chamber usually helped.