DIY Audio Projects Forum

Light bulb tester (Dim bulb tester)
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Author:  tjolle62 [ 18 Sep 2009, 21:20 ]
Post subject:  Light bulb tester (Dim bulb tester)

Hi all,
After many topics that refers to a bulb tester so im curious to what that is,
understand that is a essential tool to test amps and stuff to prevent a meltdown :o in case of wrong
placed or defective component.
please someone give me a quick explain what it is so i can build one.


Author:  Gio [ 19 Sep 2009, 15:52 ]
Post subject:  DIY Dim Bulb (lightbulb) Tester

Notes for a Dim Bulb (lightbulb) Tester are here:

And here is a video explaining the light bulb tester:


Author:  tjolle62 [ 19 Sep 2009, 16:16 ]
Post subject:  Re: DIY Dim Bulb (lightbulb) Tester

Hi and Thank you Gio,
having hard to understand and believe that so simple tool can be so extremely useful :)
now i gonna try to find a neat box for my light bulb tester.


Author:  RiGuy [ 21 Sep 2009, 11:26 ]
Post subject:  Re: Light bulb tester (Dim bulb tester)

Glad you posted a question about this circuit. It can save lives and amps and is to easy to not use.
Should be a sticky topic!

Author:  davy [ 09 Nov 2009, 11:39 ]
Post subject:  Re: Light bulb tester (Dim bulb tester)

Trouble is with lamps.... the have a pretty low filament resistance when cold which goes high when hot... the only good thing lamps can be used for is discharging high voltage smoothing capacitors in tube equipment and switch-mode power supplies, we're talking 240V 15w -100 Watt lamps here.... as well as providing light.

All depends on what you are testing with bulbs, all they tell you is yeah and neigh there is voltage there, think about it there may be voltage there OK but may well be a high resistance joint making the bulb not to light.... this can lead you a merry go round.

Gonna shoot myself in the foot here - A firm had some 12V 35 W halogens going cheap so I bought some to build a dummy load for a 20+ Amp power supply testing - I mounted two strips of connector blocks on a bit of wood and wired two groups of 6 in parallel...

... I then could either run the two groups in series on 24V or parallel them to increase the power, even one bank at 12V was highly illuminating lol... tell you what, they don't half produce some heat.

I did have a snag, the filament resistance was so low it tripped the power supplies, so the knack was to 'soft start' em.... wire a 1 ohm or 0.5 ohm power resistor in series with them and as soon as they glowed a little short it out before the filament cooled....! Well, I mean it's a darn sight cheaper than buying a proper dummy load and you can see it working!


Author:  Gio [ 09 Nov 2009, 13:10 ]
Post subject:  Re: Light bulb tester (Dim bulb tester)

Hi Dave, welcome to the forum. In this case the light bulb tester is used as a sort of variac, but the primary purpose is to identify short circuits in the equipment (typically old tube gear). The resistance of the light bulb limits the voltage that will reach the equipment. By increasing the bulb, you can increase the power to the equipment. Good for checking out old tube gear or new projects for a short.
Cheers, Gio

Author:  Geek [ 09 Nov 2009, 18:50 ]
Post subject:  Re: Light bulb tester (Dim bulb tester)

(Dim bulb tester)

Someone wants to test me? :mrgreen:


Author:  CrazzyAbtTubes [ 09 Nov 2009, 20:32 ]
Post subject:  Re: Light bulb tester (Dim bulb tester)

At last!!!!! I can unleash my evil tester in a thread I did not create!!!!!!! :lildevil:

I can show you many more uses for this thing other than providing a bit of mommentary light!

Author:  RiGuy [ 09 Nov 2009, 21:18 ]
Post subject:  Re: Light bulb tester (Dim bulb tester)

Okay Crazy,,
Whats up with all the jacks ?
What can we do with your version that we can not with the original. Do tell!

Author:  Gio [ 09 Nov 2009, 22:29 ]
Post subject:  Re: Light bulb tester (Dim bulb tester)

Geek wrote:
Someone wants to test me? :mrgreen:

It's for a different kind of dim and short! ;)

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