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Bulb Current Limiter.Hi
Bulb Current Limiter.Hi
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Old 28th May 2021, 10:10 AM   #1
BenZene is offline BenZene  United States
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Default Bulb Current Limiter.Hi

Hi, would like to know if two bulbs are needed for a current limiter if both lines are live (115VAC - 115VAC). I noticed there is only one bulb connected in series with the live wire and none on the neutral side. Am in the process of making one to test my amps which have not been used for a year and a half. Our power lines are both live unlike in other countries. Thank you in advance for your advice/help on this matter.
Benzene
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Old 28th May 2021, 10:15 AM   #2
Mooly is offline Mooly  United Kingdom
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Bulb Current Limiter.Hi
Just one bulb. The AC circuit into a piece of equipment is just a series circuit and so it doesn't matter (electrically) where in that chain the bulb goes.
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Old 28th May 2021, 10:41 AM   #3
BenZene is offline BenZene  United States
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Thanks Mooly for your advice! May now proceed wih the bulb current limiter test on my tube amps. Have done earlier a visual (on the caps and resistors) and didn't notice any physical change since I last used them almost a year and a half ago. Just wanted to be sure before I start listening to some music in my system. Thanks again and stay safe always!
Benzene
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Old 28th May 2021, 12:41 PM   #4
Mooly is offline Mooly  United Kingdom
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Bulb Current Limiter.Hi
You're welcome and good luck with the old amps
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Old 10th June 2021, 08:47 PM   #5
anatech is offline anatech  Canada
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Bulb Current Limiter.Hi
Just an alternate view.

I highly recommend a variac for testing tube or solid state equipment. With a bulb limiter your energy to the circuit is unknown and he characteristics of the limiter may interact with the circuit. Using a variac you always know (and I mean know for certain) how much voltage you are supplying the circuit. It also allows you to run the circuit at reduced voltage so you can safely troubleshoot it.

I've serviced equipment for over 45 years now. The first thing I bought past my meter, 'scope and generator was a variac. Soldering iron came first, and hand tools. Since then I have bought larger variacs and made sure they were fully "metered" with output voltage and current meters. My current one has switchable meter functions, which I am not crazy about but it works. This one does measure leakage current easily. It's a B&K 1655 AC Power Supply. Got it cheap on Ebay so I couldn't resist.

For tube amps you will need something around 4 amperes at least. I have a 10 ampere model and a 15 ampere unit as well. Tube amps draw more current on average than solid state equipment due to heater current. A 1 to 2 ampere quiescent draw would be normal for a tube amp, and that means a very high power bulb in your tester.

I know the lamp tester is cheap, but it has serious drawbacks and I personally do not think it is safe. I guess it is easier to smile and flip the switch not knowing what could happen.

-Chris
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Old 10th June 2021, 09:41 PM   #6
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by BenZene View Post
Hi, would like to know if two bulbs are needed for a current limiter if both lines are live (115VAC - 115VAC). I noticed there is only one bulb connected in series with the live wire and none on the neutral side. Am in the process of making one to test my amps which have not been used for a year and a half. Our power lines are both live unlike in other countries. Thank you in advance for your advice/help on this matter.
Benzene
Just *which* is your Country?
Why do you have 115-115VAC mains?
Is that normal in all of your Country or just in a specific place?

FWIW in the late 70s early 80s I used to live in a posh Buenos Aires neighbourhood which got electrified before others (think early 1900s), our mains voltage is 220V and my home had 220V , no doubt, but coming from 3 x 220V three phase mains, no neutral. not normal 3 x 380V + neutral, getting 220V from any phase to ground (which is the European standard).
It was NOT 110-0-110 VAC either but hot to hot.
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Last edited by JMFahey; 10th June 2021 at 09:44 PM.
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Old 11th June 2021, 12:17 AM   #7
Enzo is offline Enzo  United States
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I use a variac and meters, but really, when the OP has to ask if he needs two bulbs or not, I doubt the whole variac program will be intuitive to him. No offense intended. Further, I see thread after thread where someone keeps telling us he managed to "get the variac up to 90 volts before the resistors burnt up...again."

Shortcomings there may be, but "my light lit up bright" is darned easy to understand, even for a novice.

And of course the bulb affects circuit operation, but the use of a bulb is just for tracking down high current draw failures. It is not intended the amp will operate properly on the bulb. Once the draw failure is corrcted, we ditch the bulb.

Just my opinion.
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Old 11th June 2021, 12:31 AM   #8
anatech is offline anatech  Canada
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Bulb Current Limiter.Hi
Perfectly valid Enzo. I was just offering up another method that the OP may not have considered.

When it comes to people working on things, I sure hope they have the basics. But knowing people, I'm sure there will be smoke no matter what.
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