Uniden BC350A won’t turn on when connected to 12V transformer

[MURSman]

Hi all, I’m new to the site and I have some questions that I best should ask here.

I have a BC350A scanner mounted in a remote location, and I would like to power it off of a 12V step down transformer, the problem is I can’t get the scanner to turn on, despite everything being wired up correctly.

When powered off the regular wall connector, it works fine, but the location it’s at does not have a receptacle for plugging in the wall connector, so I have to use the outputs on the transformer.

Is there some type of switch or fuse preventing it from turning on or something?

 

[mmckenna]

One of the wires has dashes on them which signifies the negative.

That's called a 'tracer' and it does not necessarily indicate that it's the negative. The only way to know for sure is to use the multimeter.

Connecting the red meter lead to positive and the black to negative will show a positive number.
Hooking up red meter lead to negative and the black meter lead to positive will show a negative number.

Really looks like you just have had it hooked up backwards this entire time. Polarity is important...

 

[RMason]

I measured it both ways on the barrel, positive in the barrel, negative on the sleeve, negative in the barrel, positive on the sleeve, both times it read 13.03 Volts DC on the multimeter

One of those readings should be +13v. The other will be -13v. That is the critical differentiator n

 

[MURSman]

Hard to read the meter clearly, but it looks like you have the polarity backwards. When you put the red meter lead into the center of the barrel connector and the black on the outside, it looks like there is a negative sign in front of the 13.02. That means your polarity is backwards.

So, it seems that my own stupidity got the best of me, and that’s all it was lol. I was thinking of doing that at first, but didn’t really want to, fearing I would fry the scanner.

Works fine now.

 

[mmckenna]

So, it seems that my own stupidity got the best of me, and that’s all it was lol. I was thinking of doing that at first, but didn’t really want to, fearing I would fry the scanner.

Works fine now.

Ah, yeah that happens. Hopefully the explanation of what the multimeter is showing helps in the future.

Glad to hear it's working the way you want. Often it is the simple things that get you.

 

[RFI-EMI-GUY]

I was wondering if Uniden used a series or parallel reverse polarity diode. Apparently it is in series. Great that the smoke is still bottled up....

 

[Citywide173]

I was wondering if Uniden used a series or parallel reverse polarity diode. Apparently it is in series. Great that the smoke is still bottled up....

I know the 760XLT had a Zener diode in series. Made a fortune off of 5 minute repairs on those radios. Inadvertent chassis contact when plugging the power supply in would blow the diode.

 

[10-43]

What do you have a chip on your shoulder for? You are assuming BS.

No chips. Just observing this has become ridiculous. The op should abandon the project if his posts are sincere.

 

[W2JGA]

I'll be the first to admit.

I've seen worse, and I've DONE worse.

 

[RFI-EMI-GUY]

I'll be the first to admit.

I've seen worse, and I've DONE worse.

My worst was a $700 12V switching power supply, OEM part in a Motorola Portable Repeater, back in the day when they were a rare item and very crudely designed. Who would think that trying to fix one would be so very spectacular? In retrospect it had only a cold solder on a transformer leg, but my disabling voltage protection resulted in a volcano of smoke and sparks when it woke up.

 

[W2JGA]

My worst was a $700 12V switching power supply, OEM part in a Motorola Portable Repeater, back in the day when they were a rare item and very crudely designed. Who would think that trying to fix one would be so very spectacular? In retrospect it had only a cold solder on a transformer leg, but my disabling voltage protection resulted in a volcano of smoke and sparks when it woke up.

Who let the smoke out!?!

 

[mmckenna]

No chips. Just observing this has become ridiculous. The op should abandon the project if his posts are sincere.

Well, fortunately the OP didn't abandon this project. He provided detailed information and we were able to assist them in getting this to work properly.
After all, this site is about learning, and making mistakes is part of the process.

Remember, you are not required to reply to any post if you don't agree with it. You -always- have the option of leaving it to those that are willing to help.

As for letting smoke out...
I was working on a Spectra in due to distraction/inattention/not enough coffee, I hooked it up backwards. That big diode let me know.

 

[RFI-EMI-GUY]

Who let the smoke out!?!

Thats what everyone wanted to know!!!

 

[10-43]

Well, fortunately the OP didn't abandon this project. He provided detailed information and we were able to assist them in getting this to work properly.
After all, this site is about learning, and making mistakes is part of the process.

Remember, you are not required to reply to any post if you don't agree with it. You -always- have the option of leaving it to those that are willing to help.

As for letting smoke out...
I was working on a Spectra in due to distraction/inattention/not enough coffee, I hooked it up backwards. That big diode let me know.

The details are all over the place and make no sense. All have had to scratch their heads all the way through the replies.

If the idea was to hardwire to a 120 volt source, the obvious solution would have been to attach wires to the wall wart prongs and wrap in electrical tape or heat shrink tubing. Soldered or not. If the prongs dont have holes, drill some if you cannot solder. Twist them and insulate. One could also sacrifice a 2 wire extension cord. Plug the wall wart into the extension cord and cut off the wire to the right length to hardwire to 120 volts ac. The original wall wart AC is not polarized and does not need to be. The wall wart case is plastic and the pronges wire straight to the primary of the wall wart transformer. So the ac wires need not be connected in any way respecting hot or neutral.

If the op is trying to learn something, he was not very engaged in the exercise. Post, let numerous replies fly around with wild speculation, then respond weeks later.

 

[MURSman]

If the op is trying to learn something, he was not very engaged in the exercise. Post, let numerous replies fly around with wild speculation, then respond weeks later.

You do realize that most folks have a life outside of a messenger board right?

 

[mmckenna]

The details are all over the place and make no sense. All have had to scratch their heads all the way through the replies.

Well, some of us are willing to help him without getting upset about it. We walked him through it and were ultimately successful.
Plus, the OP learned how to use a multimeter to solve a problem.

That's a win in my book. And I'd do it all over again to help someone learn how to trouble shoot, rather than just spoon feed them the answers.

If the idea was to hardwire to a 120 volt source, the obvious solution would have been to attach wires to the wall wart prongs and wrap in electrical tape or heat shrink tubing.

I know hobbyists do stupid stuff like that, and I've run into similar things in the field. I'm glad the OP took the time to do it right. There's some absolute satisfaction (at least for some of us) to approach these sorts of challenges with the mindset of solving an issue correctly and safely. Sometimes it's kind of fun to solve challenging install situations with a unique approach and not just taking the easy way out.

But, hey, you do you….

 

[10-43]

You do realize that most folks have a life outside of a messenger board right?

I have been on this thread the least. Your assertion has no merit.

 

[10-43]

Well, some of us are willing to help him without getting upset about it. We walked him through it and were ultimately successful.
Plus, the OP learned how to use a multimeter to solve a problem.

That's a win in my book. And I'd do it all over again to help someone learn how to trouble shoot, rather than just spoon feed them the answers.



I know hobbyists do stupid stuff like that, and I've run into similar things in the field. I'm glad the OP took the time to do it right. There's some absolute satisfaction (at least for some of us) to approach these sorts of challenges with the mindset of solving an issue correctly and safely. Sometimes it's kind of fun to solve challenging install situations with a unique approach and not just taking the easy way out.

But, hey, you do you….

No reason to assume anyone is upset. This has been so wild I have had the impression the op has been yanking all your chains really hard for these past 4 months and laughing his a off.

 

[KevinC]

Issue has been resolved. Everyone go wait for Santa.