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Dim Bulb Tester

B

Boomer543

Active Member
Built one of these today following this link, which I believe has been posted here before:

http://antiqueradio.org/dimbulb.htm

I followed the schematic and a couple of other articles I found with a Google search, but wanted to check to make sure I got it right.

Here's how I wired it:

-- hot from plug to copper screw on SPST switch.
-- hot from second copper screw on switch to copper screw on light bulb fixture.
--hot from second copper screw on light bulb fixture to copper screw on one outlet plug.
-- broke the tab on the copper side of the outlet as per instructions.
-- neutral from silver side of outlet to wide blade of plug.

I built it to test the recap I had done on my Marantz 1060. I used a 65W bulb which was the lowest wattage I could find. When I flipped the switch on the tester, there was no light from the bulb, but the power diode on the amp lit. I was a little concerned because I would've thought that if the bulb wasn't lighting it was drawing all the power and the amp diode shouldn't light.

I shut everything off and then, like an idiot, unscrewed the lightbulb and flipped the switch back on. Again, the diode on the amp lit. I shut it off very quickly.

When I connected the amp to my speakers and an input source, it worked fine, so I know the amp is OK. I'm more concerned about whether I built the tester correctly.

Any comments or suggestions would be greatly appreciated.

Thanks,

Jack
 
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Boomer543 said:
Here's how I wired it:

-- hot from plug to copper screw on SPST switch.
-- hot from second copper screw on switch to copper screw on light bulb fixture.
--hot from second copper screw on light bulb fixture to copper screw on one outlet plug.
-- broke the tab on the copper side of the outlet as per instructions.
-- neutral from silver side of outlet to wide blade of plug.
Click to expand...
That sounds right to me. The bulb and the receptacle contacts are in series, controlled by the switch.
One quick way to test this is to make a shorting plug with an old AC plug (cut end off old lamp cord and short the wires together, or wire up a spare plug). Plug that in to the 'test' receptacle. Your 'dim light' should light normally (full bright).
EDIT:
Boomer543 said:
--hot from second copper screw on light bulb fixture to copper screw on one outlet plug.
Click to expand...

Whoa- I think your lamp receptacle should have one (or two) copper screws (the 'hot side') and a silver screw for the (usually) neutral side. If you are wiring to two adjacent copper screw connection points you may be by-passing the lamp entirely.




Boomer543 said:
I used a 65W bulb which was the lowest wattage I could find. When I flipped the switch on the tester, there was no light from the bulb, but the power diode on the amp lit.
Click to expand...
Usually I get some glow from the bulb with the initial inrush to charge the amp power supply capacitors. If the room lights are very bright this may not be so obvious.

Boomer543 said:
I was a little concerned because I would've thought that if the bulb wasn't lighting it was drawing all the power and the amp diode shouldn't light.
Click to expand...

If the amp is working properly, it acts as a 'current limiter' for the bulb. If the amp doesn't draw much current, there's not enough (in the series circuit) to heat up the bulb filament.If the amp has a short, the bulb will light and act as the current limiter.
Boomer543 said:
I shut everything off and then, like an idiot, unscrewed the lightbulb and flipped the switch back on. Again, the diode on the amp lit. I shut it off very quickly.
Click to expand...

Nothing idiotic about that. Without the bulb, no current should flow in the series circuit, and the amp should not power up.

I'd check the wiring again.
If necessary, you can post a pic.

Fun hobby, huh?:D
 
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Thanks for the response. The bulb fixture I used had two copper screws and two silver screws. I wired from switch to copper one and from copper two to the receptacle. Is there another way?
 
Sounds about right. One test is to flip the switch with nothing plugged into the outlet. The bulb should not light. Another test. Grab another device (lamp with anothe 65 w. bulb is ideal), plug in the lamp and throw the switch. You should have two lamps lit to the same brilliance.
 
Does the underside of your lamp socket look like this?
Surface%20Mount%20Light%20Socket.jpg


You need to use one connection from each side.
If you have a meter, check (with bulb out) that you don't have continuity between the connection points you've used.
You need to make sure that all the current passes through the bulb.
 
Here's a picture of the whole thing. It may have been wrong to do so, but I took the schematic literally. I wired hot to hot from plug to switch to light fixture to receptacle and then neutral only from the silver screw on the receptacle to the plug with no stops in between.

picture.php


Here's a close up of the lamp wiring. Again, I wired hot from the second copper screw on the switch to the first copper screw on the light fixture, then connected the second copper screw on the light fixture to the copper screw on the receptacle:

picture.php


I thought that if I used the silver terminals for anything, I would complete a circuit before I got to the receptacle. In other words, if I ran the neutral wire to every silver screw then I would complete a circuit at the lamp when I screwed the bulb in and would bypass the receptacle completely.

When the switch is off, no power flows. When nothing is plugged into the receptacle, the lamp doesn't light. However, I am concerned that something is wrong because the diode on the amp came on even when I removed the bulb.

Sorry for my ignorance. Any help would be GREATLY appreciated.

Jack

Sorry for being so ignorant about
 
Yep, take your neutral wire off the copper screw on the lampholder ONLY and put it on the silver screw. You have bypassed the lamp entirely, that's all.

edit: If you look at the Antique Radio sketch, in essence what you've done is attach the two wires together at the bottom of the lampholder.
 
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Bill,

Thanks for the quick response. Those are hot wires only. The neutral runs directly from the receptacle to the plug. Should I wire the neutral to the silver screws? Do I change the hot one running from the switch or the hot one running to the receptacle or does it not matter?

Jack
 
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Boomer543 said:
Bill,

Thanks for the quick response. Those are hot wires only. The neutral runs directly from the receptacle to the plug. Should I wire the neutral to the silver screws? Do I change the hot one running from the switch or the hot one running to the receptacle or does it not matter?

Jack
Click to expand...

As long as the current is flowing through the bulb, it doesn't matter.

Perhaps part of the reason for confusion is that household wiring is all parallel circuits, so that ideas like 'hot side' and 'neutral side' have some meaning. In a series circuit there really is no 'neutral side', once the switch is closed.
This does mean that the sometimes-exposed threads on the bulb are 'hot', so be sure to unplug before unscrewing the bulb. (Notice that in my version of the dim bulb, I've put tape around the bulb.....I got a 'gentle reminder' one time......)

Just look at the schematic and do some thinking about how the current has to flow through each component, and you should be fine.
 
Having trouble attaching the pic for some reason.....
One more try........

Perhaps not tonight.....
EDIT:
Funny place, AK- apparently if you have EVER attached a pic to any thread, you cannot attach the same pic to a different thread.

A much more complicated thread on the same topic is at
http://www.audiokarma.org/forums/showthread.php?t=353053

Best not to go there until things are sorted out here......
 
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Okay, let's back up a second. This is an ideal learning opportunity, there's some basic concepts here that are essential before continuing.

First, let's look at a light bulb. How does electricity flow through a screw-in light bulb? Figure that out first.

Now look at a lampholder. How does electricity flow through the lampholder and into the light bulb?

All the receptacles in your house are wired in parallel. What does this mean?

Now look at an ordinary household item, like a desk lamp. How is this plugged into a regular receptacle, how does the electricity flow?

The desk lamp likely has a switch inside. This switch is in series with the lamp. What does this mean?

NOW if those concepts have been answered, we can see how the dim bulb tester works. We want the "device under test" plugged in in SERIES with the light bulb. The switch is in SERIES also to interrupt the circuit. The lampholder must be wired to allow electricity to flow through the light bulb. It's shown and explained in the link that was posted, but it's important to know how this works.

I'm not trying to talk down to you, but rather it's obvious from looking at the way you have wired the lampholder, that it would be prudent to get an idea of the concepts down first. So actually you are to be commended for posting your work here and asking questions, that shows a willingness to learn which is critical for a DIYer.
 
nashvillebill said:
Okay, let's back up a second. This is an ideal learning opportunity, there's some basic concepts here that are essential before continuing.
...................................

So actually you are to be commended for posting your work here and asking questions, that shows a willingness to learn which is critical for a DIYer.
Click to expand...


:thmbsp::thmbsp:
 
Thanks to everyone for their posts. I was thinking about it some more last night and this morning and understand now what I need to do. Once the current passes through both sides of the lamp fixture it then goes into the copper side of the receptacle.

Will try it out when I get home later.

Again, thanks for your patience and assistance.

Jack
 
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