18Watt.com

Time to do some research and educate yourself on the topic. It’s all logic and not that hard. Just take the challenge and try to figure it out. That’s one way to solve the puzzle.
Another way is to experiment. Look, your LED will light up at 200V supply voltage as well. You can experiment with different resistor values and settle for the resistor that prevents the voltage exceeding 230V at the max wall voltage. But for science’s sake try to understand what happens when different resistances are applied. That way you can eventually calculate the current consumption of your LED and conclude that you could have achieved the desired result by just using Ohms law in the first place

Take the difficult path and educate yourself here. You will benefit from the acquired knowledge in future situations for sure!
Ask Josh where I stood 4 years ago and where his guidance has brought me.. and he almost never hands you the answer on a tray. Very very frustrating at that moment when you crave to just have things fixed. But the treasure of knowledge he’s given me by stimulating me to do the work myself is intensely satisfying.

Bieworm wrote: ↑

Fri 05/24/24 9:24 am

Time to do some research and educate yourself on the topic. It’s all logic and not that hard. Just take the challenge and try to figure it out. That’s one way to solve the puzzle.
Another way is to experiment. Look, your LED will light up at 200V supply voltage as well. You can experiment with different resistor values and settle for the resistor that prevents the voltage exceeding 230V at the max wall voltage. But for science’s sake try to understand what happens when different resistances are applied. That way you can eventually calculate the current consumption of your LED and conclude that you could have achieved the desired result by just using Ohms law in the first place

Take the difficult path and educate yourself here. You will benefit from the acquired knowledge in future situations for sure!
Ask Josh where I stood 4 years ago and where his guidance has brought me.. and he almost never hands you the answer on a tray. Very very frustrating at that moment when you crave to just have things fixed. But the treasure of knowledge he’s given me by stimulating me to do the work myself is intensely satisfying.

I agree with the general sentiment, but I don't really want to experiment when it comes to mains electricity and expensive parts. I don't have the means to test a neon with anything other than mains supply at the moment. I would need to purchase other equipment (which I may do in the future).

Is the link I put in my last post relevant? That will help me in the short term.

tatter75 wrote: ↑

Fri 05/24/24 10:50 am

Bieworm wrote: ↑

Fri 05/24/24 9:24 am

Time to do some research and educate yourself on the topic. It’s all logic and not that hard. Just take the challenge and try to figure it out. That’s one way to solve the puzzle.
Another way is to experiment. Look, your LED will light up at 200V supply voltage as well. You can experiment with different resistor values and settle for the resistor that prevents the voltage exceeding 230V at the max wall voltage. But for science’s sake try to understand what happens when different resistances are applied. That way you can eventually calculate the current consumption of your LED and conclude that you could have achieved the desired result by just using Ohms law in the first place

Take the difficult path and educate yourself here. You will benefit from the acquired knowledge in future situations for sure!
Ask Josh where I stood 4 years ago and where his guidance has brought me.. and he almost never hands you the answer on a tray. Very very frustrating at that moment when you crave to just have things fixed. But the treasure of knowledge he’s given me by stimulating me to do the work myself is intensely satisfying.

I agree with the general sentiment, but I don't really want to experiment when it comes to mains electricity and expensive parts. I don't have the means to test a neon with anything other than mains supply at the moment. I would need to purchase other equipment (which I may do in the future).

Is the link I put in my last post relevant? That will help me in the short term.

Your link should be adequate to determine the resistor value. And.. equipment? You just need a DMM. Don’t say you don’t have one. That is the most essential piece of equipment you need to build an amp. I think you’re thinking too big of this subject. There’s no lab equipment involved

Here's one way to conduct an experiment:

Leave the LED out of it. Leave the amp unplugged.

Connect a sufficient DMM that can handle higher voltages with alligator clips (should have been included with the probes - usually screw on). Set it to ACV. If your DMM cannot handle at least 600V, and have decent probes, get a better DMM and/or better probes.

Take two resistors of sufficient wattage per your calculations and connect them to the correct terminals on your transformer (one each) then connect the other end of the resistors to your DMM alligator clips, making sure that they're stable and not shorting out on anything.

Then plug in the amp, and switch it on. See what the voltage looks like on your DMM. Do not touch or modify the test circuit while the amp is plugged in. After powering off, and unplugging the amp, let the resistors cool off before removing them, as they might be hot. If they're too hot, you need higher wattage resistors.

If you don't feel comfortable doing that, then you should switch to the 6.3V lamps, and still be extra careful.

Mains voltages are scary, but they're lower than the in-circuit voltage. Practice good safety precautions, or bring the amp to a tech to help you.

Thanks,
Josh

Thanks, my extra probes for my DMM just arrived funnily enough. I will have a play around now you’ve given me a clue how to go about it.

Bieworm wrote: ↑

Fri 05/24/24 11:08 am

tatter75 wrote: ↑

Fri 05/24/24 10:50 am

Bieworm wrote: ↑

Fri 05/24/24 9:24 am

Time to do some research and educate yourself on the topic. It’s all logic and not that hard. Just take the challenge and try to figure it out. That’s one way to solve the puzzle.
Another way is to experiment. Look, your LED will light up at 200V supply voltage as well. You can experiment with different resistor values and settle for the resistor that prevents the voltage exceeding 230V at the max wall voltage. But for science’s sake try to understand what happens when different resistances are applied. That way you can eventually calculate the current consumption of your LED and conclude that you could have achieved the desired result by just using Ohms law in the first place

Take the difficult path and educate yourself here. You will benefit from the acquired knowledge in future situations for sure!
Ask Josh where I stood 4 years ago and where his guidance has brought me.. and he almost never hands you the answer on a tray. Very very frustrating at that moment when you crave to just have things fixed. But the treasure of knowledge he’s given me by stimulating me to do the work myself is intensely satisfying.

I agree with the general sentiment, but I don't really want to experiment when it comes to mains electricity and expensive parts. I don't have the means to test a neon with anything other than mains supply at the moment. I would need to purchase other equipment (which I may do in the future).

Is the link I put in my last post relevant? That will help me in the short term.

Your link should be adequate to determine the resistor value. And.. equipment? You just need a DMM. Don’t say you don’t have one. That is the most essential piece of equipment you need to build an amp. I think you’re thinking too big of this subject. There’s no lab equipment involved

Ah gotcha! I do have a decent DMM, I was confused when you said to try a lower voltage as I don’t have anything to do that. Thanks.

I meant dropping the voltage on the lamp with a resistor. Nothing fancy

I get that now, but you need to spoon feed this stuff to novices like me

Tried out a few resistors and to get approx 25volt reduction in the voltage I seem to require a 1M resistor.

My mains voltage is between 230 and 245 volts, the label on the back of the amp says 230v / 630ma.

Using ohms law I need a 39.7 ohms 15.75 watt resistor. So I'm a bit confused

Lol! Don’t confuse things. The current consumption in your equation is only the current that the lamp consumes, not the entire amp’s current draw

Is 630mA the PT current limit? There's no way a small indicator lamp should draw that much current.

I don’t know what the current draw is for the lamp. Can I measure its resistance and work the current from that?

I think I’m fundamentally misunderstanding something.

My train of thought was that my neon can handle 230v but my mains is putting out 245v therefore i need to reduce the feed going to the neon by 25v. When i experimented with different resistors I needed a 1meg resistor to achieve that.

But I have no idea if that’s the right approach and/or how I apply ohms law to work it out.

If the 1M resistor gets you there it is ok. What wattage is that resistor?
Do you have a spare lamp to check if things work now?

It’s a 3 watt resistor. But that’s just what I had to hand.

I will test a lamp with it tomorrow to see what happens.

tatter75 wrote: ↑

Sat 05/25/24 4:53 pm

It’s a 3 watt resistor. But that’s just what I had to hand.

I will test a lamp with it tomorrow to see what happens.

3W is better. Higher power handling is better.

The point of my test with the resistors and a multimeter is to see what AC voltage you get before involving the lamp.

So with the lamp wired in the voltage after the resistor drops to around 70v supplying the lamp. This means the lamp is working but VERY dim. But at least it hasn't blown.

I suppose the next experiment is to try a lower value resistor instead of a 1M?

So my question is why is the voltage lower? Is that the current draw of the lamp now being in circuit?

tatter75 wrote: ↑

Sun 05/26/24 6:09 am

So with the lamp wired in the voltage after the resistor drops to around 70v supplying the lamp. This means the lamp is working but VERY dim. But at least it hasn't blown.

I suppose the next experiment is to try a lower value resistor instead of a 1M?

So my question is why is the voltage lower? Is that the current draw of the lamp now being in circuit?

Yes. Now you can start lowering the resistance. Leave the 1M in and try some resistors in parallel. Maybe start with another 1M resistor, so that way you get 500k due to the paralleling.

I would suggest what I already suggested...higher wattage, and between 470Ω and 1KΩ. You're way above what's needed.

Bieworm wrote: ↑

Sun 05/26/24 8:46 am

tatter75 wrote: ↑

Sun 05/26/24 6:09 am

So with the lamp wired in the voltage after the resistor drops to around 70v supplying the lamp. This means the lamp is working but VERY dim. But at least it hasn't blown.

I suppose the next experiment is to try a lower value resistor instead of a 1M?

So my question is why is the voltage lower? Is that the current draw of the lamp now being in circuit?

Yes. Now you can start lowering the resistance. Leave the 1M in and try some resistors in parallel. Maybe start with another 1M resistor, so that way you get 500k due to the paralleling.

2 x 1M in parallel results in 100v, 3 x 1M in parallel results in 115v. So I'm way over what I need.

JMPGuitars wrote: ↑

Sun 05/26/24 10:52 am

I would suggest what I already suggested...higher wattage, and between 470Ω and 1KΩ. You're way above what's needed.

Do I need to go higher than 3 watts?