Something a bit different to my usual..

[rubber_jonnie]

Next on the bench for me is something I have been meaning to look at for a while, as it seems like a possible easy fix.

It's a 40 channel CB transceiver.

PXL_20220623_150343587.jpg

PXL_20220623_150405487.jpg

The main problem is that it doesn't run at all off batteries, but it does work off a 12V PSU. Hooking up a PSU to the battery connectors, and I see that the power does reach the board, but it doesn't switch on.

So deeper dive needed to see why we aren't powering up from batteries, as it's kind of not portable if you have to use a PSU to get it going!!

It looks like somebody has previously attempted repairs, as there is some sketchy looking soldering inside.

I'll give it a damn good clean whilst it's apart too.

[stephen_usher]

Eek! Analogue stuff! :-)

[rubber_jonnie]

Eek! Analogue stuff! :-)

Very much so, and I haven't found (And doubt I will) a schematic yet!

[PhilC]

Another interesting project, probably a diode that’s supposed to block the psu input from the batteries would be my guess?

[mrbombermillzy]

From the little I can see of the battery terminal springs, they look like they've had a touch of the battery rot. I can see bright green!

Are you sure it's not those? (Perhaps you are connecting the PSU on a better/conductive part of the metal?)

Besides, it must be worth a try... you must be getting withdrawal symptoms re: repairing battery damage by now, surely? :lol:

[rubber_jonnie]

Another interesting project, probably a diode that’s supposed to block the psu input from the batteries would be my guess?

Yeah, a diode was on my list too, and there is one, but there is also a charge port and I'm wondering if there is an issue in the charge circuit, so again, diode or other component

[stephen_usher]

Maybe the charge input jack disconnects the battery and the contact in that switch has corroded?

[rubber_jonnie]

Maybe the charge input jack disconnects the battery and the contact in that switch has corroded?

That's a good thought, I'll take a look thanks.

[rubber_jonnie]

Ok, so the lack of any sort of schematic has really been a huge pain, however looking closely under a bright light I noticed that there was a diode and capacitor that were installed in the wrong slots, so diode where the cap should be and vice versa:

PXL_20220629_185027882.jpg

It looked very like it was that way from the factory, so I'm now wondering if it ever worked.

So after switching I had battery operation but then the mains adaptor no longer worked. The long and short of that was a broken, now fixed trace.

Here it is in all its glory:

PXL_20220629_214955852.jpg

And it now happily runs off either battery or mains adaptor, or a 12v adaptor if in a car. I can't find a suitable barrel jack in my spares to test charging, and TBH I'm not too worried about using rechargeable batteries in it.

I think I may get my original Xbox on the bench next, as I hear the supercapacitor used for the clock circuit has a habit of leaking, and I really don't want to have to repair that!!

[Tomswork]

Nice repair. I will turn my old cb on to c19 and listen. And I may need to adjust my flux capacitor 1971

Tom