Testing dollhouse circuits and bulbs

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My multimeter arrived today. I cannot get to the wiring underneath the dollhouse because there is paint and glue drying. ;-)
I tried to get a voltage reading at the light sockets inside the doll house. I could not get a consistent reading. The space is very cramped and the sockets very small (3/8"). I seemed to get a better reading on DC than AC. The DC readings jumped all over the place, but it looked like between 0.9 and 1.1 v. The AC readings jumped around even more. The most consistent reading was 6v at one socket.
Is there a way using this meter to tell if the current is AC or DC?
Next, I did a continuity test of the bulbs themselves. Of the 12 bulbs I removed from the house, only one passed the continuity test.
I then tried a resistance test on the bulbs. The one that passed the continuity test showed 11 ohms of resistence. The rest showed infinite resistance.
I then took the good bulb and tried it in several sockets. After fiddling with the button switches, I was able to get it to light in several sockets. It was very dim.
When everything dries, I will try to get under the house and see if I can get better readings.
Any comments or suggestions?
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As part of the upgrade you should make it Energy Star compliant by using CCCCFL bulbs. ;-)
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On 12/20/2011 3:24 PM, DerbyDad03 wrote:

Where can you get teeny tiny CFL bulbs? o_O
TDD
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On Tue, 20 Dec 2011 22:43:06 -0600, The Daring Dufas

From Keebler Light Products. They are made by elves.

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On 12/21/2011 3:33 AM, micky wrote:

Hey, The Keebler Elves aren't that small, it would have to be CFL fairies. Oh darn! I think we have a number of those working for our government. o_O
TDD
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Welcome to the wonderful world of electrical troubleshooting. I have about 20 meters (maybe 30) because they are indispensable for electronics work. Some hook to PC's for recording work, some are small and lighted that I keep in my car. I keep one in my camera bag, one connected to the battery powered sump pump and even have a AA-A battery charger that reads the voltage of each cell as it charges. My wife says it's a sickness but I believe you can never have enough multimeters, flashlights or rechargeable batteries. (-:

For testing like that I might make up a test prod from a dowel about the size of the bulb with a screw in the center to simulate a bulb, but that's probably a bit much for you just starting out. It takes a delicate hand to read a micro-socket when it's on a test bench. Mounted in a doll house might be much harder and close to impossible without the right probes. One the backside of the socket there are often screw terminals. That would be a good place to check the socket voltage.

That's a good question. Measuring an AC voltage using a high quality, accurate voltmeter, that set to measure DC volts, should, by definition result in a reading of zero volts. The reason you read a small residual DC voltage when measuring an AC voltage might be because of small inaccuracies in your meter. Any true AC voltage has absolutely no DC component. I would test it using a diode - even an LED would work - that will pass current in only one direction. But that's little advanced. I suppose you could test the circuit by reversing the probes. If it's DC, the + and - signs should reverse themselves when you switch the probes. With AC, it shouldn't have any effect.

Excellent work! With an old dollhouse and the possibility that the bulbs are getting more voltage than designed for, it's very likely the only problem is burned out lightbulbs.

That sounds right. Infinite resistance means the filament is broken and the bulb is dead. You should be able to confirm that with a magnifying glass. If they were run at double their rating, the filament damage should be very obvious and might include blackening of the bulb's interior.

You may also be experiencing problems with dirty switch contacts and dirty or corroded bulb sockets. The center button connector of the socket should be nice and shiny in each socket. I bet they're not.

I don't think you have to do a complete rewire - if it were 110VAC passing through those wires you would have seen the bulb go supernova and possibly pop. There's got to be a transformer somewhere. By getting the bulb to light in several sockets you've conclusively proved they can not be wired in series (in a chain like old Christmas lights where if one bulb went dead, they all died). That's important to know.
Trace where the AC wires comes into the dollhouse and find the transformer (apologies if you've already done this - I just started reading this thread.). If it's well wired to the cord and the cord's in good shape, I wouldn't rewire the unit. Switches can often be "decrudded" by operating them a few dozen times to scrape off the oxidation.
I think the next step is to clean the sockets, cycle the switches, install the replacement bulbs and take it from there.
-- Bobby G.
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On Tue, 20 Dec 2011 17:20:01 -0500, "Robert Green"

I don't have the tools for that ;-(

I can't get to the back side. The sockets are mounted in the ceiling. On the first floor, it's about 1/2" thick and completely finished. On the second floor, there is an attic, but it's sealed. I don't want to start taking it apart.

I thought I got a +/- change one time, but it's so difficult to get at the sockets, that I can;t be sure I'm getting good contact and not shorting the probes.

I ordered a bunch of 2.5v #14 bulbs. They should be here tomorrow.

The filaments all look OK. A couple are somewhat blackened.

The switches are definitely at least a little suspect. They are the push-button type. They are a little loose in the housing and if I jiggle them, the lights flicker. I can't see into the sockets, but the house has been stored in garages on the east coast (humid) for many years. I might go get a mirror on a stick and see if I can see into the sockets. But if they are corroded, there ma not be much I ca do without taking the while thing apart, which is too much for this Christmas.

Yes, I'm quite certain that it's not 110 and probably not AC.

Yep, I was glad to discover that.

The AC cord is one of those really old fabric-covered types. The place where it goes into the base of the house is just a hole in the wood with no fitting or stress relief. There is no obvious wear that I can see, but it all seems a little unsafe to me.

I managed to get under the house. The whole bottom is covered and glued shut. I'm starting to think that this wasn't that well made. I'm tempted to cut the cord and go without lights for now. If the little girl really gets into it (right now she's more into Buzz Lightyear), I'll consider taking it apart and installing LEDs and a battery pack.
Anyway, thanks for the thoughtful and patient help.
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On Wed, 21 Dec 2011 02:02:00 -0800, Jennifer Murphy

I like to flick the bulb with my finger. Often a filament is broken but the gap is so small, I can't tell until I do that, but after that, the filament vibrates for a couple seconds. If it vibrates, it's broken.

That makes it much harder, but if you measure the voltage anywhere, and bought bulbs that will work with that voltage, the burnt out bulbs are probably the only problem with most sockets.

Do you have a pencil with an eraser or the top, or a ball point pen with an ink eraser on the top? These are probably too big, right? but you can use a knife to make the eraser part smaller Cut from the end down, instead of the side in.
But don't do anything until your correct bulbs don't work. I live on the east coast too, NYC and Baltimore and haven't had trouble with socket corrosion.

That would mean batteries.
OTOH is the house plugged into the wall?

So it IS plugged into the wall. In that case t here is probably a transformer, not at the wall (that's a new idea) but attached to the house or maybe in a little corner of the house, right where the wire goes into the house. If the house is older than 1955? or so, I'd be very surprised if there was anything to turn the AC to DC. (Even if it's much newer) So why did you say abve that it's probalby not AC?
The place

Don't do that. Just unplug it. You'll have new ideas as the winter goes on, and time to work on it, but if you cut the cord, you'll probably never fix it.
I have an electric heater from 1947 with a cloth covered cord that is in perfect condition. So is the heater itself. My mother bought it to warm the bathroom when I was new-born. OTOH, I have seen old wire whose insultation is crumbliing. You may want to cut off that part that is crumbling, if any, but leave as much as possible so you don't have to break into the house to add more cord if the cord at the hole is good.

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wrote:

That's a good idea. A pencil should fit just fine. I'll try that when the new bulbs arrive.
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wrote:

the
glass.
very
Gawd. It's late at night and my vision's blurry so I first read that as "I like to lick the bulb" thinking to myself: "Is Micky CRAZY?!" (-: Anyway, yes, that's a good way to find a broken filament. I think Jennifer's continuity tests are probably accurate even if she can't see the filament break.
Are you living in Balto now? We've got enough posters in the Baltowash area that we should have a get-together. If we've got enough people, maybe we can convince HD or Lowe's to cater a lunch where they can make a sales pitch while we eat free food. (-: There's one of each in Laurel, which should be accessible from DC and Baltimore.
-- Bobby G.
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On Thu, 22 Dec 2011 01:20:25 -0500, "Robert Green"

P&M
LOL

Yes, you're right, and I might be wrong in that flicking and licking probably doesn't work well for really small bulbs. I do that mostly with 60 watt bulbs, or automobile turn signal bulbs (the big ones, made for American cars and real men.) and maybe one size smaller.

Yes, I'm in Balltimore. A get-together would be great. I read another group and we had one and it was a lot of fun.

Laurel is fine.
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about
keep
rechargeable
that's
That's too bad, but understandable. After thinking about, I would break one of the dead bulbs, cut a small jumper wire in half and solder the bare wire ends to the bulb's contacts. Jumper wires have alligator clips on each. Cutting one in half leaves a bare end and an end with a metal clip that you can clip to your meter probes. I could fabricate such a "tester" in less time than it took to type this message but I have the tools. I'm aware that you don't. I'd be happy to make up a socket tester for you gratis but it wouldn't happen until well after Christmas. I can't imagine testing the sockets any other way. It's hard to hold the probes correctly even with the socket on the benchtop. But when mounted upside in a the tiny rooms of a dollhouse? Sounds like torture from the Spanish Inquistion! And nobody expects the Spanish Inquistion (if I didn't say it, at least 5 Monty Python fans would have).

One
be a

I don't blame you. Once upon a time when I first started rebuilding Brit sportscars, I came across this humorous comment in a "how to" book: "Carburetor" is a French word that means "leave it alone." The same could be said of your antique dollhouse's electrical wiring.

The
DC
inaccuracies
would
in
should
have
I totally understand. It's a job for a specially made test probe.

I
That's where the rubber meets the road. I suspect you'll get more than a few working. Who knows? If you clean the sockets and cycle the switches, they might all work.

the
glass.
very
dirty
should
You can use the rubber eraser end of a small pencil inside the socket to clean off the oxidation. Make sure to blow out the rubber particles with canned air or a little makeup brush.

passing
possibly
I would guess that the AC line cord goes into a small transformer that outputs from 2 to 5 VAC. Lightbulbs don't care whether they run on AC or DC so I don't see any reason for the designer to have a rectifier in the house that converts AC to DC. It would be an extra and unnecessary step for the builder and I'm guessing if he omitted strain relief on the line cord, he was on a real budget.

in
That's what leads me to believe there's a small AC transformer at the end of the line cord. It should be heavy enough to be detectable in some way. It might even put out a hum that's detectable by a close-by AM radio.

transformer
You're right. I would replace the cord with a more modern one and add strain relief if it's not too hard to access the point of entry. If it is. I would probably use some low-temp hot melt glue to create one. Not pretty, but it's held when I've had to do it. You could cut the cord a few inches from the hole and slide protective tubing of some sort to protect the wire's insulation. Then either solder a newer line cord, the old line cord or an in-line power switch to the bit left sticking out. You could also wrap the cord that sticks out of the hole with a enough layers of black electrical tape and then push that bulge into the hole to create strain relief of sorts. Old cloth covered wire without a strain relief bothers me. I've rebuilt items with similar cords that looked intact but that crumbled in short order when they were flexed just a little bit. On the other hand, most of the original wiring in the my house is cloth covered. I've since added new circuits with 12/2 romex to take most of the load off the old wires where I could. But I digress . . .

install
That sounds like serious deconstruction of the house would be involved. I'd wait and see how it goes over first. Rebuilding using LED's and batteries or a small wall wart (the plug in transformer-rectifier that are used for chargers and such) It might be a perfect teaching opportunity to involve the youngster with. You could even buy some cheap solar garden lights and turn it into a solar powered doll house. (-:

That's why we're here. Well most of us. A few seem to think it's open mike night at their local comedy club, but that's Usenet.
-- Bobby G. - It's 58F degrees at night in December in DC. Maybe global warming theorists are right!
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On Thu, 22 Dec 2011 01:11:18 -0500, "Robert Green"

I heard on the radio that it was 55 at 6 in the morning, in Baltimore. That struck me as strange.
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yabbut, it was legitimately cold last week (NoVA) so it all evens out. Ish.
nate
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wrote:

<< yabbut, it was legitimately cold last week (NoVA) so it all evensout. Ish.
nate>>
You gotta admit it's been weirdly warm for the last couple of months. I can remember some God-awful cold at this time of year. We've had major and serious snowstorms happen on Nov. 11 and killer frosts in October. When I first moved in the temp dropped to 6F and the furnace overloaded it cycled so fast. It's almost Christmas and it's 61F here. That's not right! (-:
-- Bobby G.
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On 12/22/2011 11:32 AM, Robert Green wrote: ...

...
Well, we had a whole bunch of 70F Christmas days/weeks when I was a kid some 45-55 year ago but I can't recall one out of the 40s at best the last 10-14 years or so. Right now were 65 on Sat/Sun and snowing and blizzard conditions Tues and snowing again today lightly.
Things change and there are and have always been short and longer term cycles and folks remember only a _very_ short time...
--
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On 12/23/2011 3:10 PM, Robert Green wrote: ...

...
Far SW KS, yes. 3F this AM. Not sure whether this front is going E that far or not at...
--
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wrote:

It's been like that for a while. My heating bill is half of what it was for the same period last year. I don't mind that. I just hope we don't see a string of 100+ F degree days in the summer. I dislike the heat a lot more than the cold.
-- Bobby G.
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On Thu, 22 Dec 2011 12:28:23 -0500, "Robert Green"

You can always put on more clothes, but there's a limit to how naked you can get (fully naked is the limit and not even that in public.)
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On Sat, 24 Dec 2011 22:37:53 -0500, "Robert Green"

I hadn't read that here. Good idea. I guess I coudl do that, but since I only do my house, I go up around 5 in the morning, after the roof fan ran until about 10PM .
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