I have a faulty knob

[nrh]

No word of a lie! ;-)

My NEFF (Naff?) built-in combi microwave oven has a knob whose sole purpose is to enable the setting of the cooking time duration on the LED timer display.

Over the last few months, it has developed an irritating habit of selecting whatever random value it so pleases at each turn of the knob, instead of incrementing numerically in the normal manner. Are you still following me? Good! The problem can be alleviated a little by gently depressing on the knob (no, keep up please) whilst simultaneously turning it. However, it is still very difficult to control, and a game ensues lasting several minutes with each of us trying to outwit the other and much cussing!

Does anyone know if it is an easy problem to remedy, and if so how, please?

Thanks for listening. :-)

Nigel

[Ian Stirling]

Given the intermitten nature of the fault, it seems that cleaning the element which senses rotation, or the bit which rotates, could have positive results. However, microwaves are the most lethal domestic appliance to repair, with plenty of energy to make early electric chair makers jealous.

What electronics skills, if any do you have?

[nrh]

In news:43dd0282$0$82627$ [e-mail], Ian Stirling scribed:

Hmmm... thanks for the tip. ;-)

I've a C&G in Cookery? :-)

OK, dangerous stuff this then. I was wondering if there was any sort of canned cleaning agent I could get to blow around the orrifices and improve the connection?

It feels like the knob is spring loaded with a ball bearing-type thinggy forming the connection and clicks in and out of some sort of detente or channel. So I was wondering if it was those pits or channels that were gunged up and needing cleaning out to improve the contacts? The adjacent push buttons are sticky too and don't glide in and out smoothly anymore, preferring to stick whilst depressed and pop back out after some seconds have elapsed, instead of immediately they have been released by the finger.

N.

[Dave]

I am guessing here, but it sounds like the knob is connected to a wheel that has slots in it. What happens, is a light shines through the slots and is detected at the other side by a pair of receivers. The direction of rotation is detected by checking which of the two receivers alters first. What usually goes wrong is that the shaft bearings get worn and the receiver gets totally confused by the wobbling wheel. I have a communication receiver built along these lines and it suffers the same fault. Unless you can remove any back lash/wear on the shaft, then you will have to buy a new control.

HTH But I may be totally wrong.

Dave

[meow2222]

Your knob is pressed onto a faulty potentiometer, enough to upset any man. Spray cleaner might work, might not. If not, time for a new pot. Cheap and simple, but yes you do need to take a few necessary precautions when dealing with your knob in the microwave.

NT

[nrh]

Ah, yes. A bit like the wheel on a mouse (computer) you mean? Quite possible, indeed. Looks like its a heave-ho, and down to see the repair man job. Now, who can I take it to? GOOGLE!!!

Thanks Dave. ;-)

Nigel

[nrh]

What do you recommend? Cillit Bang?

I always take precautions when interfering with strange equipment. ;-)

Nigel

[Owain]

Ooh what a nasty thought.

Owain

[meow2222]

oh lord no. switch and pot cleaner. Not real sure whats in it, maybe someone here knows. Some kind of non-conductive solvent.

NT

[nrh]

'sok, just my soh. ;-)

N.

[meow2222]

silly me thought you were serious. Would hate to think of you spraying that on your knob. It'd bring tears to your eyes.

NT

[manatbandq]

Sounds more like a rotary encoder than a pot.

Does the knob stop after less than one turn or just keep going round and round?

MBQ

[Ian Stirling]

WD40 is likely to do least harm, of commonly available stuff. It even may make it work for a short time.

As to whether it's pressed onto a potentiometer. Can you turn it forever, or does it come to a stop?

[nrh]

In news:43de1f66$0$82673$ [e-mail], Ian Stirling scribed:

Yup, got some of that. I'll give it a squirt.

Forever.

N.

[nrh]

In news: [e-mail], [e-mail] scribed:

It's an 'Ariston' knob. It goes on, and on and on and on and on. (in both directions)

:-)

N.

[The3rd Earl Of Derby]

I read somewhere that WD40 has a corrosion element hence why it frees rusted parts as it breakdown the rust by corroding it?

-- Sir Benjamin Middlethwaite

[Ian Stirling]

It is possible that through cost-cutting, the maker decided to use metal contacts, not optical sensors. In this case, WD40 might temporarily help.

[manatbandq]

Rotary encoders of this sort (the ones that look like a pot) are almost invariably metal contacts.

MBQ

[meow2222]

Makes sense, but still wd40 is not the thing to use. It is a mix of oil and solvent, and leaving oil on there is a recipe for more trouble. It attracts muck like a magnet, and makes a sticky mess. Not what you need for a knob. Use a proper cleaning solvent.

NT

[The3rd Earl Of Derby]

Sir Benjamin Middlethwaite