T.V. Remote Question

[whisky-dave]

mmm yes, what have you been 'watching' ;-)

[fictitious]

Dirty devil...:-)

[John]

I thought you were perfectly clear.

[Malcolm]

I have had this type of problem without the spill!

The buttons were in a sheet of 'rubber' which I assume was a conducting polymer (rubber like material). The remote became less and lass effective even after changing batteries. When I dismantled it there seemed to be an oily film on the circuit board, concentraded in the position of themost commonly used buttons. I cleaned this off and about

6 months later the problem recurred.

My suspicion was that the film was coming from the polymer membrane - the only cure was regular cleaning

Malcolm

[Anton Gÿsen]

My Marantz CD player itself has lain on the floor for some years.

[jon.in.durham]

The very same thing is happening to my Sony remote for my Freeview set-top box, but I have to keep opening it up every week to clean the grease off the circuit board. The buttons are in some sort of silicone-rubber pad with some black substance underneath which makes contact with the circuit board.

Worst affected buttons are 1 and the sound and channel up/down buttons

I used to think this was only happening to me!

[fictitious]

Seems like it wasn't the tea spillage that was responsible but what you and others say about the oilyness...

[Dave]

The rubber is conductive, but you should have taken the opportunity to rub the printed circuit contacts with a pencil eraser to clean them.

Regards

Dave

[Arfa Daily]

not. Instead, both the pads and the interconnects are formed from a deposited carbon-doped paint-like material. This should never be abraded, even with a pencil rubber. A cotton bud moistened with electronics grade (99.7%) IPA is as agressive as you should ever get with the contact areas.

Arfa

[Arfa Daily]

So this one is a good point in question as an example of when I said in my earlier post that "sometimes, it's just time for a new one ..."

Arfa

[John]

Some people don't realise that there is a circuit to slightly delay to the signal - to prevent accidental operation. They use this slight delay to press ever harder on the button to make something happen. The result is increased wear and even broken circuit boards.

[michael adams]

Wrong. Do you know how fast electrons travel through a conductor ?

And in any case how would any circuit be able to distinguish between accidental and deliberate presses.

Wrong. This is exactly what they need to do. Press harder. Any "delay" to prevent accidental operation is purely mechanical and is provided by the elasticity of the rubber keys which can absorb a certain amount of pressure before the pressure is transmitted to back of the key and it touches the circuit board .

michael adams

...

The result is

[michael adams]

If that were the case then it would be happening more often, to more people.

Whereas it clearly isn't.

Since I started wrapping all my remotes in clingfilm I've never have any problems.

Any sticky liquid drink seeping into the remote and eventally working its way onto any part of the circuit board and drying out will cause shorting. There's no possible way that it couldn't as its a good conductor. Quite possibly film from cigarette smoke might even have the same effect although that's more of a guess.

michael adams

...

[Bartc]

They've taken this to extremes with my V+ box and it's remote:

Either it doesn't register at all, or it registers (and a tiny LED on the box confirms this, if you happen to be looking at it instead of the TV), but sometimes it does nothing with it for several seconds.

Your reaction of course is to press the button once or twice more. Whereupon it takes these several key presses which have now queued up and executes them rapidly one after the other, usually completely screwing up whatever it is you're trying to do. Sometimes, it completely ignores any key presses for up to maybe a minute.

Now, when you press a button and nothing happens, and you weren't looking at the LED, you have to make a decision as to whether to wait to see if there's a reaction to this press, or decide to chance a second and possibly self-cancelling press...

And even when it clearly registers the action immediately, it likes to take change channel in it's own good time. A few weeks back I was using an old

17" table top TV; you pressed the buttons on the front, and the channel changed instantly! I kept changing channels just for this novelty.

[John]

I remember - the term is "Anti Bounce" - The circuitry expects to see a deliberate input for (say) 50 milliseconds. (possibly a capacitor is used) Anything less will be seen as an accidental touch on the button. Pressing harder only creates stresses in the circuit board and can degrade the conductive coating on the back of the buttons. (Press long - not hard!).

This delay reduces spurious commands being sent to the TV.

Of course there is always the six shooter approach where the remote is flicked with a wrist action towards the set. Many people find that this helps!!!!

[John]

The old TV Tuners were mechanical marvel! Remember the "Turret Tuner"?

De-bounce:

This circuit is used to eliminate contact bounce when using a push switch with a digital circuit.

What is Contact Bounce? Contact bounce occurs with all types of switches. As the switch contacts meet and then separate again there is a brief point at which the contacts are just at the point of separation. This can cause a moment of uncertainty where the contacts may or may not be passing current. The whole episode lasts for only a few milliseconds at most but due to the speed of electronic circuits, each splutter from the switch contacts is seen by the circuit as a legitimate push of the switch. The result is that the circuit sees several switch operations instead of just one.

I suppose that eventually we will become 'tuned' to pressing a buttons for the required time - rather than stabbing it. After all, using a mouse became intuitive.

[Bob Eager]

Ah, that's because it gives the infra red waves a bit more speed as they're flung out of the end!

[PCPaul]

Simplest thing is almost always to point it at a mobile phone camera. You see the IR LED light up white if it's working. It's worked on every one of at least half a dozen phones I've tried it with - I guess the extra few pence for a decent IR filter on a mobile camera is too much to bear.

[Arfa Daily]

"michael adams" wrote in message news: [e-mail]...

??????????? How fast electrons travel is neither here nor there. Just about any circuit which employs input from a physical key or switch, employs a technique called de-bouncing, which causes the remote processor IC or key matrix interface IC or system control IC or whatever is the appropriate input device in whatever equipment we are talking about at the time, to ignore any change of state on any of its input lines for a pre-programmed number of internal clocks. Once the input has ben stable for that number of clocks i.e. the switch contacts have stopped bouncing, *then* the input device takes whatever action is indicated by whichever button, key or switch has been activated. The delay is short in human terms - usually only a few mS - so it's unlikely that any operator will notice that the reaction to a button press is anything other than instantaneous. Which does rather knock on the head any pause to make sure that a button has been deliberately rather than accidentally pushed. I can certainly never remember in over 35 years of repairing equipment which uses remote controls - ultrasonic, infrared, or wireless - encountering one where there was a deliberate long anti-accident pause. There is an additional delay introduced, allbeit another short one, by the fact that the receiving processor will wait until at least two complete frames of identical data have been received to ensure that no corruption of the data has taken place in the transmission path. Many 'digital' TV sets take an inordinately long time to respond to a channel change remote control request, but this is a function of the way that the TV has to find the new data stream requested, lock onto it and process it into a change of 'channel', rather than any delay in the actual remote control system.

Sorry, but this is not the case at all. The 'poor contact' problem is most often caused by the conductive rubber contact lozenges, breaking down chemically. Extra hard pressing of any such affected buttons, merely exacerbates the problem, and leads to a faster complete cessation of the functionality of the button(s) in question.

Arfa

[Arfa Daily]

You are merely seeing the difference between an analogue channel change, where all that happened was that the frequency of the tuner's local oscillator was shifted as a result of sending it a single data byte, and changing data stream in a digital multiplex, which is a complex operation, requiring the processor to drop the existing data stream, look for and identify the requested new one, lock onto it, frame it, wait for a new 'whole' picture to be transmitted, process it, write it to memory, read it back out and display it ...

Arfa