Fixing on-off button my car radio

[Lobster]

My car radio has a combined on/off push-button and rotary volume control. It's become progressively more difficult to turn on and off over recent months - you have to push increasingly hard to get a response - to the extent that it's now almost unusable. Rotary (volume) function is fine.

So I've laboriously extracted the radio and pulled it all apart today in the hope of finding something readily fixable, and have kind-of come to a halt now. Here's the offending bit:

I can feel the on-off, spring-loaded clicky function of the switch, apparently feels fine; no hint of anything wrong. Is there anything that can be done without unsoldering and replacing the component? If I have to do that (and I'm not very confident with a soldering iron, when it's all so tiny) - how would I identify the correct part (and as a one-off is it going to be easy to obtain?

I think ideally I'd just like to drop this little PCB in a jiffy bag and send it somewhere for repair - can anyone recommend anywhere that would do this?

(This is an OEM Vauxhall Zafira CD-radio by the way).

Thanks David

[John]

Servisol Switch Cleaning Lubricant? (Maplins)

[Graham]

How about having it it permanently ON? It would still be switched off when parked and when driving and you can just turn volume to minimum when not wanted. If this work around/bodge is acceptable, then it would be a very simple soldering job to bridge the on/off part of the combined switch/volume control. From the photo it looks almost 100% certain the two pins on the left are the switch pins. Just join them together to have power permanently applied to the radio. It looks like the pins go through the board to the other side and it would be easier to make the bridge between them on that side so as not to risk melting part of the switch/volume control. The three pins on the right are almost certainly the volume control. You can test this in advance if you have a multimeter. Try for contiunity between the two pin on the right (that is if you can get it to switch on). If not, then put the meter on the two outer pins on the right. It should read about 10,000 ohms. (anything from 5000-20,000 ohms)

If unsure about soldering, I'd first suggest you melt two fresh blobs of solder on each pin (hold for 2-5 seconds until smoke from flux appears). Then it will be easier to attach the small bridge of wire. Tin the wire ends first by holding the wire in pliers or tweezers and melting solder onto them and then melt the whole lot to the pad on the printed circuit board for 2-5 seconds. No need to use insulated wire for this short hop between pins. A piece of 15-20 amp fuse wire would be ideal. Just let it lay flat between pins and keep it very still until the solder has set (5 secs). You will want to hold the wire with small long nose pliers or tweezers. If you use pliers, hold wire at far end as pliers will act as a heat sink and it will be difficult to heat up the wire enough to melt the solder. When done, hopefully the solder joints look shiny. If they look crystaline its because the joint was moved when setting If that happens, then re melt them with the addition of a tiny bit of fresh solder.

I would have suggest switch cleaner (Electrolube or Servisol spray) but that switch/volume control looks tightly sealed. If there is a tiny gap somewhere you could try squirting some in and briskly switching it on and off to clean the contacts. I don't hold out much hope for that though.

Graham

[Dave Liquorice]

As the switch feels fine naked that would indicate that it's a mechanical problem with the knob. Gunk or sticky stuff shaft where it passed through the front panel?

I suspect this is a "soft" switch and actual power control is down by the radios CPU. Simply shorting the contacts may or may not have effect of permanently powering the set and may stop other pushes of other buttons registered...

[Harry Bloomfield]

Lobster has brought this to us :

The tiny size of those tracks to the switch suggest to me that it does not actually switch any current, so it probably just a a push to make switch - open when the pressure is released. All it will do is signal the microprocessor to turn the radio on if it is off, or off it is on.

[Graham]

Having looked again, I think you are correct. Probably momentary action. Switch cleaner then and if still causing trouble after that, the only solution is to replace.Might be cheaper/easier to find a replacemnt radio from ebay.

Graham

[Dave]

Not too sure of the scenario here, but if the op has a rubber membrane on a printed circuit track...

Wash the membrane in soapy water, brush with a soft brush (a soft tooth brush works fine) rinse and dry. Then clean the tracks with a pencil eraser. This removes both the residue of ingestion between the key pad and the PCB.

HTH

Dave

[Adrian C]

Lobster wrote: how would I identify the correct part (and as a

This possibly looks like a combined momentary push button and either a potentiometer or rotary encoder going by the functional description and the splines on the shaft. Tricky. :-|

A make (VDO perhaps?) and model number of the radio might be worthwhile for a google search. What is it?

With this you have "Outside chance #1". The number might find you the service manual on the net which would give a parts breakdown and identify the manufacturer and part ID. There are some manuals up at and a few assorted (mostly russian) websites.

If it is VDO, you could buy spares and manuals from them. As an individual I have, but yeah - if it's gonna cost their administrative costs then the eBay replacement route for the whole radio might be better (or a facia adaptor so you can slot in another make radio).

Or "outside chance #2". If you were to unsolder the component, sometimes you'd find markings (manufacturer logo and part ID) which also would find something on Google.

Or "outside chance #3" - if you could identify the pushbutton traces (separate from the rotary control) and find a space on the front panel, you might be able to bodge another pushbutton switch in there, or relocate wires to another switch not used much.

Another chance for a bonus. Mention here (or on sci.electronics.repair) the model number and a guy running a car radio repair / decoding business would reply to this thread with exciting news of the contents of his scrap pile ....

... and might be also prepared to do that for you (and no doubt a couple of soldering iron wavers on this group once you have the switch!)

So model number :-) or a picture of it so we can trawl through eBay :-)

[John Miller]

This may not be any help, but have you asked a Vauxhall dealer how much it would cost to replace the switch? I ask because my car radio exhibited exactly the same symptoms and was replaced by my dealer (Citroen) for 5.95 GBP - much to my amazement. The radio is OEM but is manufactured by Blaupunkt

John Miller

[The Natural Philosopher]

Isn't removing the PCB a bit drastic, Dave?

[Graham]

He is thinking of the rubber mats that you find behind keyboards, always used in TV remote controls. Taking those out and washing them does a good job, but doesn't apply here. As shown in the picture, this is a volume pot and switch combination and by the looks of it there are no little gaps to get any switch cleaner spray into. They do not come apart either. If lucky, the OP might get some switch cleaner inside by spraying the whole thing and letting it run down the knob spindle overnight. Worth a try, but not holding my breath. I doubt the contacts are worn. Probably just a little oxidised and only need a bit of cleaner to touch them for it to help. You could try soaking the whole switch/pot in switch cleaner and leave overnight. If you could spray out enough switch cleaner into a small container and dipped that corner of the board into it, it might seep inside the switch overnight. Certainly won't do any harm to anything on that board.

Graham

[Lobster]

Thanks for the advice, all.

What solvent is switch cleaner? IPA? Not having any to hand, will meths do the business?

Actually I'm now regretting not having pulled off the control button before removing and demolishing the radio; I now realise that it's possible that's where the problem lies; ie, the radio might work fine if I just push the metal stub of the switch. Will have to reassemble and check that out before doing anything more drastic; however it would be worth trying the switch-cleaner trick first.

David

[Bob Eager]

No, switch cleaner is, well, switch cleaner, e.g.:

[The Natural Philosopher]

I guess I ahoud have put in a smiley.

Read again carefully.

"This removes BOTH the residue of ingestion between the keypad AND THE PCB."

Its the full stop behind the PCB that does it. Or the BOTH. What does it remove. BOTH. Both what? what is the second part of the pair? Why, simple. It removes both the dirt AND the PCB!!!

QED.;-)

[Graham]

Only use switch cleaner. Not meths or sugical spirt or anything else. I'm not being pedantic. Using anything else won't do the job and may harm plastics, pcb lacquer etc or dry out lubrication of moving parts. Link from Johns advice earlier

[Lobster]

OK, will do: think I might source somewhere a bit cheaper than CPC's at

31 quid delivered for 200 ml!! stone the crows, what is this stuff?!

What's the difference between that and this ebay version at 3.75 GBP?

David

[Bob Eager]

That's weird - but it was merely an example. I usually get it in a little pen.

[Chris Whelan]

[...]

No idea, but I've bought the Servisol product from that eBayer and it's fine.

Chris

[Duncan Wood]

I think that's per case. AS

£5.85 or Maplin sell it.

[Dave]

As usual, I probably was not too clear. After removing the rubber membrane, you are usually looking at the PCB that is connected to the rest of the electronics. This PCB has the switching tracks on it, (usually it is gold plated) but can get dirty for a variety of reasons and only requires a rub with a pencil eraser to clean it.

Dave