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Refurbishing TV remote controllers 
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Joined: Thu 03 Jun 2010, 18:56:03

Posts: 1628
Location: Soviet Venezuela
Post Refurbishing TV remote controllers
Lately, the RC of my Samsung CRT TV started acting wonky: suddenly stops working without warning, or some buttons fail to register keypresses, requiring several attempts. Of course, the first thing I tried was replacing the batteries, but with no luck - fresh AAAs didn't fixed anything (I checked all batteries with a multimeter - voltages were healthy).

Before you say "Just go and buy a universal controller", I refuse to do this due to several reasons: 1) they're EXPENSIVE -remember, I live in some country en-route to a hyperinflation, and these things are very scarce in stores right now-, 2) the only model you can find in stores is some RCA garbage which is known to be very unreliable -family members had those, and they often lose the programming code-, and 3) You lose features (like being able to enter the TV menus, or using advanced features like MTS/SAP or quick image presets). So my only option here is to fix the original controller.

The first time it started to act this way, I cracked it open - there were no signs of corrosion, blown components, or obvious cold solder joints (I did found the dreaded "Lead-Free" logo there). The prime suspect was a 4.7uF/50V electrolytic capacitor (everything else is: a 3-leg crystal, a resistor, a ceramic capacitor, the emitter IR LED, and a ~24-pin SOIC IC which I gues it's the microcontroller), and trying to test it right there yielded odd reads (in the order of <1nF). Since I had nothing to lose, I desoldered the capacitor and tried to replace it, but I didn't had a matching cap in my toolbox. I decided to recheck it anyway now that it was off-circuit: this time it tests OK! (~4.78uF). There were no bulging tops or any signs of a leaky cap (the TV itself is ~3 year old, and the remote control PCB seems to be made in late 2009). I resoldered it, and BAM! Suddenly the control started to work again!

Today the same shit happened again: this time I redid the procedure: desolder cap, test it, resolder, controller is now working... partially. Now some buttons fail to register keypresses (POWER, Volume UP, 1/4...). The PCB button pads weren't worn, and they were clean. In fact, testing with a graphite pencil tip, ALL buttons work, so I suspect the rubber membrane contact pads are starting to wear down. I retouched some of those with the same pencil (I had to do the same thing years ago with another remote controller), and now the buttons work, but now I must hold down those for a couple of seconds until they start to work.

So, my questions are:
1) Is it safe to replace a capacitor with a lower or higher value on this kind of circuits? I only have 1uf, 6.8uf and 10uF electrolytics at hand. (Suppose the one and only electronics store in town is out of 4.7uF parts).
2) Aside of the graphite pencil method, is there a most effective way to "refurb" rubber membrane contact pads?

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Tom Maneiro
- http://mi.tsdx.net.ve -

Wed 25 Jun 2014, 18:49:17

Joined: Wed 06 May 2009, 04:13:19

Posts: 4543
Post Re: Refurbishing TV remote controllers
tomman wrote:
2) Aside of the graphite pencil method, is there a most effective way to "refurb" rubber membrane contact pads?

Cleaning them with a pencil eraser(lightly!) helps sometimes.
Or you can say "fuck it" and glue bits of aluminum foil to the carbon dots. You don't need a carbon bridge, you just need to short two terminals, and metal is GOOD at shorting things.

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Wed 25 Jun 2014, 19:23:56

Joined: Sat 15 Aug 2009, 07:35:02

Posts: 77
Post Re: Refurbishing TV remote controllers
tomman wrote:
1) Is it safe to replace a capacitor with a lower or higher value on this kind of circuits? I only have 1uf, 6.8uf and 10uF electrolytics at hand. (Suppose the one and only electronics store in town is out of 4.7uF parts).

Depends what they are connected to, but likely not, it won't break it but it might affect the signal so that the tv set will not be able to recieve the signals.

/Zorbeltuss

Thu 03 Jul 2014, 04:01:12

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