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.
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.
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.
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.
How are they connected? If you can get one light to work in a socket, it's parallel.
11 ohms cold seems about 5x too high for that bulb. You sure you've got #14 bulbs?
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. #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.
If it's a battery, it won't last long. If it's AC, the transformer should be as big as your fist. If it's much smaller, it's gonna have a lot of secondary impedance. What that means is that it's sized for max load. Designed properly, the lamps will work fine. Problem is that one burns out reducing the load and the voltage goes up increasing the stress on the others. Like dominoes, they start failing at an increasing rate. That's why you've got one left that works. There's another more subtle problem. About 70 years ago, the line voltage increased from 110 to 120V. The life of a bulb goes down MUCH faster than the voltage goes up. That can be a problem for a bulb with a design life (at proper voltage) of 15 hours.
Your problem is likely bad connections in the circuit. This can be corroded connections at the socket or corrosion inside the socket where the lamp contacts it or corrosion on the bulb itself. Sometimes, people just twist wires together to make connections. After 70 years, corrosion causes the connection to fail. You might measure unloaded voltage at the end of the lamp string, but a bulb won't light in that socket.
You should have two wires leaving whatever powers it running together in parallel throughout the house with each bulb tapped into the pair. If you can tell where the wire runs, you should be able to tell, from which sockets work and which don't, where the break is.
You can measure the resistance of the wiring, but it's sensitive to contact corrosion at the probe point and it's easy to infer a break where none exists. Remember to short the probes in ohms mode and lock the range so you won't see all the autoranging artifacts.
If you put the lamp in the far end of the wire, you can measure the voltage at each socket. But if access is limited you risk shorting the connection and smoking something.
From the symptoms, I'd guess that you have corroded connections AND the wrong bulb type.
What's the voltage at the supply end of the circuit with the one-good bulb burning?
You have one good bulb and 11 dead ones. There has to be a transformer somewhere in there. They are not running 120volts to those bulbs. If you can find replacement bulbs, you are in good shape, the transformer may be weak, causing dim lights.
I know you want to make the house authentic, but I still say that for cost and safety reasons, get a string of LED christmas lights (which do come in sets of 12), and fit them in so you dont see the actual bulb. Make a little shade around them out of a paper or plastic (LEDs do not get hot). This will save lots of cash, time, and be much safer.
You could even use the existing wires, use a 6volt DC wall wart transformer and solder in LEDs (with resistor) to each socket, and never have to replace bulbs or worry about safety.
I very often use a jumper wrie with alligator clips on each end, especailly for connecting the black test lead of the meter to a grouond, or anywhere I want it connected. That leaves both hands free to use the other test lead. I buy ten 12" wires for 3 or 4 dollars at Radio Shack, and I clip one end to the metal proble of the test lead.
For small things, I put a hat pin, or corsage pin, or straight pin, or headless nail thinner than the original probe in the alligator clip at the other end. So I can test i cramped areas.
For a doll house, if it's plugged into the wall, it's AC. If it runs on batteryies it's DC.
IIRC, you can measuere DC current with an AC meter. The reading will be wrong, but consistent and proportional to the actual value. The RMS iirc. This is with an analog meter. Not sure how digital meters behave.
On the other hand try to meaure AC with a DC meter and the average value will be zero. Because the *average* voltage of AC *is* zero. On an analog meter that's what it will show. Not sure if it would jump around with a digital meter, or not.
Dolls have excellent vision, and don't need much light to read. Don't forget, that if they are only 3 inches tall and you are more than 60 inches tall. the light seems 20 times brighter for them.
They might help to identify the replacement she needs. They may be better marked** than the one good bulb. Plus she won't have to carry the one good bulb with her when she goes out to get replacement bulbs.
I don't throw away bad parts until I have everything working.
**Which is not to say the OP needs exactly what was in there before. Only that the base fit the socket and the voltage be right. Different makers of bulbs may well use different part numbers, for example.
(My father made a picture album in 1936, and in 1990 I went to a lot of the same places and took a lot of the same pictures. I wanted to add facing pages to his album, to show the changes in 53 years, and I wanted to use the adhesive corners to hold the pictures, like he used.
(Most camera stores had clear vinyl, which of course have the advantage of letting one see the corners, but I found one store that sold the black paper corners my father used, identical, complete with the same error in part of the embossed line.)
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.
Now dangerous are 6 or 12 volts light bulbs, or the wires supplying them? You can't even feel the current with your hands, only if you put the leads on your tongue. (OTOH, 110 volts on your tongue are very very bad.)
How much cash can she possibly save?
OP, go to a toy store or doll house forum and ask about replacement bulbs. Also look here:
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.
I don't recall anyone saying not to buy an autoranging meter. One or two said not to buy any meter at all, but it seemed like they were just jerking me around.
If the autoranging can be turned off, then why is it such a big deal not to buy an autoranging meter?
I don't see any way to turn it off. It does have a battery test mode with settings for 1.5, 6, 9, and 12 volts. Can I use that?
This is the meter:
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In another thread, I explained that there is a 110 AC cord going into the base of the doll house. There's a sealed compartment underneath that I assume houses a transformer of some kind.
Yes. I didn't know that when I posted before.
I have no idea what bulbs I have. The marking are illegible. I have a bunch of #14s on order. I'll see what they do.
With the meter set to ohms, the readong says "0.L" and the units says "M ohms". If I short the leads, the display jumps around a bit and then settles down at between 0.0 and 0.6 ohms. It's closer to zero if I short at the tips and slightly higher if I short nearer the base.
The meter is brand new, so corrosion should not be a problem.
15 hours? What possible use would there be for such a bulb?
I can't get at the actual transformer without taking the doll house apart, which I don't want to do right now. However, the housing where I think the transformer is placed is about 6" x 6" x 1".
Are you confusing load and voltage?
It's been almost 40 years since college physics, but my recollection is that the voltage drop across each branch of a parallel circuit is the same. So, from E=IR, the load (amperage) is the inverse of the resistance. No?
If they fail at an increasing rate, the odds of having just one left working would be small, no? Once all of the others are done, the last one would go very quickly.
I can't get to most of that to check. The bulbs look clean.
Yes, I'm quite sure that it's nowhere near 110 at the sockets. My guess is that (a) it was once 2.5 vdc and is now somewhat weaker or (b) it was originally 1.0-1.5 vdc for a softer light.
For now, I'll probably replace the bulbs and see how much works. Later, I may consider replacing the transformer with a battery pack and use LEDs with an E10 base.
Start by finding out the voltage requirements of the bulbs, then see if your power supply is working properly putting out the right voltage for the bulbs. Replace all the bulbs while you at it, sounds like more are bad than good. This will make further troubleshooting easier and may solve all your problems to start with.
Continuing on, I bought an old doll house several years ago and it had problems with lighting too. After replacing the bulbs I found that several of the switches were bad. The one house is the limit of my experience and my local hobby store owner was the source of all my info. Oh yeah a little contact cleaner in the light sockets helps too. I use DeOXit. I recommend using this on all the bulbs and switches.
Get a lightbulb that fits into the socket. Wrap it in cloth and whack it gently with a hammer. You want to break the glass. Once you've done that cut the filament. Now you can measure the voltage on each filament wire.
I've had those size bulbs in my hands, years ago. Your suggestion is sincere, but I really doubt that it's practical. The inside wires are too small, too close together. And the bulb inside the doll house is going to be in an odd direction.
That ranks up there like breaking a popsickle stick or tongue depressor with enough wood left connecting the two halves. We did that (unsucsessfully) for a cub scout project.
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