On Thu, 22 Dec 2011 03:51:30 -0500, "Robert Green"
wrote:

"mike" wrote in message
...
Jennifer Murphy wrote:

stuff snipped

Any comments or suggestions?

First problem is that you ignored advice and bought an autoranging meter.
TURN OFF THE AUTORANGING.
Dig around in the manual and look for range hold or range lock or
something similar. Set it to the 20V range (maybe 40V depending on the
meter) and leave it there while measuring voltage. You'll have to lock
it again if you change modes.

Considering future uses as well as the current one, I think she did fine
with an autoranger. I think it's far more useful to a novice than a
dedicated range meter and probably less expensive, too. The problem is
obviously getting the probes in place to read the voltage.

You've given few details, but some assumptions can be made.
There are always exceptions, but usually...

Where does the power come from?
If it's a battery, it's DC.
If it's a transformer, it's AC.

What if it's a transformer with a rectifier? (-: (But I don't think so in
this old a device.)

How are they connected?
If you can get one light to work in a socket, it's parallel.

That's been established. They're parallel.

2.5 vac 0.3a #14 flashlight bulbs x 12 = 3.6 amps.

11 ohms cold seems about 5x too high for that bulb. You sure you've
got #14 bulbs?

Damn you Micky, now I have to get up from my nice warm bed to grab some
bulbs and my ohm meter.

[time passes]

I got a reading of 1.1 ohms for my bulbs so you're right. I suspect an
autoranging decimal error of some sort or skin contact interfering with the
reading. Several of my bulbs in storage had substantial corrosion on the
button contact that affected the readings as well.

Short the meter leads and measure resistance of the leads. It's never
zero and sometimes a lot more if the probes are defective or just cheap
or connections are corroded. Subtract that number from your bulb
measurement.

I don't think it matters much as dead bulbs are an "either/or" proposition.
Dead or not. Some small resistance or none at all. If she has an audio
continuity function, a beep is good, none is dead.

#14 MINIATURE BULB E10 BASE - 2.47 Volt 0.30 Amp Miniature Screw (E10)
Base 0.50 MSCP, C-2R Filament Design, 15 Average Rated Hours, 0.94"
Maximum Overall Length #14 Miniature Bulb

NOTE that it's rated for 15 hours average life. Might wanna change
to a different bulb. Then you'll need a different transformer, but
12V bulbs on a 12V surplus laptop power supply works well. Cheap
non-regulated wall warts have small transformers and have serious
regulation problems as noted below.

That is pretty rotten life expectancy but is completely in line with almost
all the bulbs being burned out. Have you come across many 12VDC laptop
supplies? Everything I've got runs from 15 to 18VDC. Maybe times have
changed. The key word in finding a power supply for this app, as you've
noted, is "Regulated." Unfortunately not all regulated power supplies are
marked thusly but a simple check with a voltmeter usually tell you. All the
unregulated power supplies I've tested run several volts above rated voltage
without load. .

And with a bulb in the circuit, there IS a load - and the voltage
drops.