Power Supply Question

[ronmicha]

I've lost my AC Adapter to my Radio Shack scanner which called for a 13.8V w/ 500mah. I've got another Radio Shack adapter which is a 12V w/ 500mah. Can I use this without blowing up the radio? Seems I recall that as long as the voltage is lower it's okay; but if it's higher you're in danger of harming the radio.
Thanks.
Ron

 

[jonny290]

Yeah, you should be fine.

Make sure that the positive/negative assignments are the same. Most consumer electronics is center negative (to allow for passive AC/battery switching) but some gear is center positive (to reduce shorts).

 

[Raven95150]

Chances are your original AC adapter was 12V. Most electronics that are designed to be able to be hooked up in a vehicle call for 13.8V because most vehicles run right around 14V when the engine is running and just under 13V when not running with a fully charged battery. Even though they call for 13.8V, the AC adapters are usually 12V. Before hooking it up to power, make sure the plug fits correctly and has the proper polarity. There should be a diagram illustrating the polarity on the scanner near the plug and on the AC adapter. DO NOT hook up power unless you are sure of the polarity or you may seriously damage the scanner.

 

[N4JNW]

Yeah, as mentioned above, check polarity and you're good to go!

 

[jonny290]

Conversely, though, if you actually put a voltmeter or scope on a wall-wart output, it's usually about 5-10% higher than rated voltage and slightly dirty DC, so you'd probably get a decent 13v out of it anyways, at least not while heavily charging.

 

[N4JNW]

Yeah... I'd bet money if you took your "12V" power supply you found, and put a voltmeter on it, I'd be willing to bet it's not 12V right on the money..

 

[roadranger]

bought battries?

I just recently learned that those wall chargers are regulated ac/dc converters, capacitized to replace batteries otherwise used to run your scanner. just don't charge NiMH in a NiCD scanner. That is where your batteries get hot (boil) and they die prematurely.