• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Help wiring up anLED Bar

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#21
So what you are say is that they may flash on AC?
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They will flash to fast to be seen, they will just appear dimmer than normal

How can I test to see if it is AC or DC?
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I would imho suggest that you read the sticky thread on safety practices if you haven't already done so.

Will some thing like this work?
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Looks OK to me but a second opinion would always be welcome

How do I figure out what I need for a resistor
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This might help LED calculator for single LEDs

I would go with the capacitor value and diode series chosen

Brgds Bill
 
#22
Yes, that circuit with the single diode and capacitor and current limiting resistor works well in this application. I am doing exactly that with the front panel led indicator and an unused heater winding in my latest project.

For resistor value, just google led resistor calculator, there is a plethora of online calculators, and even iphone aps!

Cheers,

Chris
 
#23
Sorry, I didn't realize that it should be AC!!! Of course, being a heater. I'm not accustomed to tubes!
Some simulations/tests and you will find the best configuration of LEDs, resistors, caps and diodes! If I find some time I will test here as well.
Cheers,
Max.
 
#24
Sweet jeebus, you guys are making a PhD thesis out of a simple LED lamp.

Use voltage doubler on 6.3V transformer winding to get 15+V DC. Use LM7812 to turn that into regulated 12V DC. Hook up your 12V DC LED lamp. Swith the amplifier on. Enjoy the illumination.
 
#25
I must say I hate this kind of discussion in the forum, where everyone points in a different direction!!! Arnulf told the right thing. I only disagree in the regulation with a 7812. The doubler and a resistor to limit current would do the job and be much easier to assemble, being cost effective and reliable.
If you guys read the thread about lighting an LED directly from mains through a 240K resistor only, this one would be really a thesis!!!
All the best,
Max.
 
#26
You are right, it is not rocket science 😉

I was wiring up an amp this afternoon. It has an illuminated power switch with a built in LED and dropping resistor specified as requiring 12 volts DC. I had a spare 5 volt AC heater winding, so simply used the single rectifying diode and capacitor to get about 6.5 - 7 volts. Works a treat, even though 12 volts specified on switch.

Cheers,

Chris
 
#27
There's more than one way to skin a cat :trapper:

As I happen to have spare bridge rectifiers, caps and regulators etc, I also would have gone down Arnulf and the Gimps road.

However there is a nice simplicity to the method proposed by the Dogger and used by Chrish and welcome having the choice.
 
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#28
Soonerorlater said:
There's more than one way to skin a cat :trapper:

As I happen to have spare bridge rectifiers, caps and regulators etc, I also would have gone down Arnulf and the Gimps road.

However there is a nice simplicity to the method proposed by the Dogger and used by Chrish and welcome having the choice.
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Yeah, agreed! Though I have spare regulators, caps and diodes, I am building monoblocks with three regulated supplies per block. Another regulated supply simply to power the power indicator LED looked a bit unnecessary 😉 On a previous build I needed about -12V for CCS, so regulated and used the same supply for the same LED indicator switch. If the supply is for a string of effects LEDs, a small regulator circuit is probably what I would do too.

Cheers,

Chris
 
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