RS Wall Wart

C. Sullivan feedle at feedle.net
Sat Jul 19 01:25:10 CDT 2008


On Jul 18, 2008, at 7:15 PM, William Donzelli wrote:

>> Could you give more information?  RadioShack has made at least three
>> different products with that catalog number.
>
> That is all I have. Just a sticker, basically saying to use the  
> 270-1551.

Okay, but.. like, does it plug into the wall?  A cigarette lighter?   
Does it take the modern "Adaptaplugs" (the ones with two pins on  
them), the older friction-fit barrel style, or is it one of those  
"four plugs on the end of a wire, with a 9V clip" dealies?

Again, usage of basic tools that anybody who is even remotely serious  
about collecting this stuff (a $5 voltmeter) would likely answer your  
question for you.

> I do not want to invest ten bucks into something that is probably
> worth ten bucks. I do not have anything else that uses C cells.

Wow, what kind of gadget geek are you?  I've got old freebie  
flashlights from Radio Shack that date back to the Reagan  
Administration that use C cells.  And I'm not by far the oldest guy  
out here on the list.

Also, you do know that in a pinch AA batteries and some duct tape make  
wonderful C cells.  AAs are the same length and voltage: rolling them  
up with duct tape to make them thick enough to not rattle around works  
wonders in a pinch.  Note that you'll drain them in a hurry, however.

As a side note, many NiCd "C" and "D" cells (and more than one NiMH  
I've seen) are just AA batteries in bigger shells.  One of the battery  
makers even sells a kit that includes the sleeves to turn rechargeable  
AAs into Cs and Ds.

> Yes, I do indeed have power supplies of all flavors.

Supply.  One.  See my notes below: a junk drawer full of wall-warts is  
a poor substitute for a real laboratory power supply.

> They are a bit hard to get to, and I would rather not break open the
> case. I would rather just use my crappy universal wall wart thing, if
> I knew the settings.

Hang on a second, I want to make sure I understand your request,  
because in your haste to handwave my help you may have answered your  
own question.

You have a device that takes 6 C batteries, which is of low enough  
value to you that you won't spend a pittance to purchase the proper  
batteries for.  You have a power supply of unknown origin, that you  
think is a Radio Shack #270-1551.  Is that the power supply you  
received with the unit and it does not work?  Or, is that the power  
supply you have, and you want to know if it will work?

I'm going to out on a limb here and assume that you are trying to use  
a variable power supply wall-wart with one of those little slider  
switches on it to do different voltages (is that the Radio Shack #  
270-1551?).

In this scenario, there's a 50/50 chance that the device requires the  
same voltage from the wall-wart that it would get from the batteries.   
I refer you to my previous answer.   A "safe" answer would be to start  
at 3V, and step it up until you find the minimum voltage that would  
operate the device consistently.

The polarity is a big question: you could do one of three things to  
determine that.  1: use a meter to attempt to find which side of the  
power plug on the back is tied to the negative battery terminal, 2:  
open the device and see which side is the likely "ground", and  
therefore, the negative, or 3: just plug it in, and pray to the gods  
that the polarity protection diode is still good enough to keep the  
unit from going "poof!" and flip it if it doesn't work.  All this, of  
course, assumes that the original device doesn't have an AC  
requirement, or had "connector conspiracy" to require you to purchase  
a replacement factory supply.

You still have a BIG potential problem.  Just about all the wall-warts  
I've ever seen with the little slider switches from 1.5-12VDC on the  
front are 150mA supplies, at least up until a few years ago.  Just  
about any "pong" machine (or similar device) would probably not  
function properly with only 150mA.  Worse, most cheap supplies of this  
type will sag as the load exceeds the rated maximum: so while it might  
indeed be 9VDC at 100mA, at 175mA of load it can drop to 7.5V or lower.

If you have any serious interest in classic hardware, you _MUST_  
invest in a lab supply.  You can mail order one for well under $100 (I  
use a Velleman one that cost me $50 at Fry's Electronics in Portland,  
Oregon), and if you live in a "major city" you should be able to find  
a surplus house with one for peanuts.  If you fancy yourself handy, or  
want to learn soldering skills, Velleman makes a 1A kit power supply  
that is more than adequate for a lot of this kind of stuff AND has the  
bonus of being real easy and fun to build. It is $12.95 from Ramsey  
Electronics (www.ramsey.com).  A proper lab supply will allow you to  
give anything you find the RIGHT power, cleanly, and with overcurrent  
protection that could save the device from frying.

I think you might be laboring under a "false economy" here.  You don't  
want to spend money on dry cells, but you are unwilling to "break the  
plastic" (which might not even be required anyway, there's more than  
one way to skin that cat)?  Either the unit has value, in which case  
it is worth doing right.. or it doesn't, and who gives a load of  
dingo's kidneys if you snap the plastic to get at the terminals!     
What's the deal?



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