Dual control info required for Cobra 29LX Radios please.

[163TM847]

I have two of those controls pulled from a scrap S9 different make but same thing, Although one of them was for the echo so may not work as a volume and i cant remember which was which, I am sure the knobs from the original control will go straight onto the 148/360 type and in correct position, But the tab on the 148/360 type control would have to be bent out the way as that is in a different position, The original control is easy to repair/swap parts over as they come apart quite easily and because the on/off switch of yours is faulty thats even easier to fix if you had a similar one with same on/off mechanism as you would only need to swap the very back part.[See bottom of my post]

Does yours still have a nice click when you switch on/off ? If so take the power wires off the on/off switch part and test the switch contacts with a continuity tester to see if you have no continuity with it off, and continuity with it on, If it does then its not the switch.

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Tabs in different position, Original on top, 148/360 on the side, But both controls flat side in same position in the off position.

Controls.jpg

I also have this ALPHA control which is bent, But the on/off mechanism is good and will should go straight onto yours, If your one does have a faulty switch.

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[The Collector]

Cool, cheers Nick and thanks for explaining it for the likes of myself

It does have a nice-sounding and firm click when rotated, which is worrying then.

Fair play to the seller though. I got the offer of 2/3rds of my money back (which I obviously accepted), so I can fork out for bits (messing about looking for them) and repairs.

I'll have a play with my meter to check for continuity later (that's about all I can do with it!). I'll update this later with my findings.

[The Collector]

Right, I unsoldered the switch altogether and the back 2 connections (I think the switching point?) have no continuity when it's switched off and continuity when it's switched on...as it should be. I think they had continuity either way when soldered in place but I forgot to write it down before I got the soldering iron out.

This would make me think, as you said Nick, that there's a short/fault somewhere providing constant power then?

If I'm right in thinking, if I powered up the radio now, it shouldn't turn on with the switch missing, so I'll try that at some point when next in the loft to check and if it does, the switch is fine and it's something else.

[The Collector]

As suspected, the radio fired up without the switch in place, so it's getting power from somewhere it shouldn't be. Any ideas which component is being a bit naughty? If it's a tiny surface-mount thing though, it may have to wind its way to a certain rig doctor's.

Could this possibly be a dreaded CPU problem. I know there were multiple issues with them and possibly the reason they stopped making them.

Could I simply wire the on/off switch into where the power comes into the back of the radio, so the switch cuts off the power before it gets to any components at all? (uneducated animal that I am).

[163TM847]

I dont think it will be a CPU problem if the radio is actually working, Plus the on/off is an old fashioned manual switch, I would follow the power cables that were connected to the on off switch all the way back and see if someone has jumped something.

[The Collector]

Thanks Nick, I'll have a good mooch and see if I can see anything untoward, although unless it's pretty obvious, I'll struggle to find it

I was thinking of using the rear connections of the switch (on/off) for simply switching the 12v + from the power lead just inside the radio, but I'm not sure if these switches can handle 12v??? What are your thoughts folks, about this option if I can't find anything wrong?

[astradyne]

It may also be worth checking out the foil side of the PCB. Someone may have been in the radio with a soldering iron and bridged the power rail. There should be no voltage whatsoever getting to the radio with the wires disconnected from the rear of the power switch.

I once had a 360FM which wouldn't switch off. On looking inside a previous owner had removed both wires from the back of the volume/squelch pot and soldered them together. My first thought was that the pot was faulty, hence the mod. But after doing a continuity test and reconnecting the wires to their rightful place everything worked perfectly.

Obviously this scenario isn't exactly the same for your radio, but the issue is the same. Someone may have fettled the radio so it remains on no matter what. There are all kinds of bright ideas in CB land...

[The Collector]

I'll have a good look both sides then when I get the chance. These new surface-mount radios are a lot harder to spot the usual "old" problems on I must say.

Here's the pic' of it fired up without the switch in place. Wires are all separated and not shorting onto anything.

[The Collector]

Well I had a good look at the component side of the board and saw nothing apparent.

On the flat side, there were a few areas that looked a bit dodgy, so I soldered anything that looked remotely crappy, including stuff on the pic's below.

Nothing made any difference though, so I wired the positive wire from the power socket to the volume on/off switch and from the other side to the power wire on the board. It all fires up as it should now on the switch and I've safely wrapped up the 2 wires from the switch that weren't doing anything.

The solder seemed difficult to heat up so may be that free-free sh**. "Heath Robinson" it may be fixing the issue that way, but it works for me...and the boxed, mint radio only cost me £27 after the refund so I'm chuffed.

Thanks for all the replies guys