Advanced Lightbulb Limiter Question.

[dragonbat13]

LOL!

No really.  What I want to know is how does one choose what wattage lightbulb to use? 

These days I'm using a 40 watt. But from using that I feel like I should use a higher wattage.  Incandescent bulbs are not as easy to find, although they do look cooler these days.

[pdf64]

It depends on what current the load connected to it is expected to draw.
eg initial wiring test with no valves, use a low wattage bulb.
Final check of 100W amp, very high wattage bulbs, maybe a pair of 100W in parallel.

[Willabe]

The lower the bulbs wattage, the more protection for the amp your testing.

Say, for a Princeton, Deluxe, 15w to 20w amps, 60W bulb would be fine, go up to a Super Reverb, 40w amp, maybe 75w to a 100w? You could probably use a 60w bulb for a 40w amp.

Then go to a 100w bulb for anything 80w  to 100w?

I have some 40w bulbs, probably be enough for a SE Champ, 5w amp. I have some 20w bulbs that I might use for a preamp with just a few 12 _ _ 7 tubes?   

[acheld]

Appliance bulbs are incandescent, usually in the 40W range.  These are widely available and are exempt from the ban of "household" incandescents.

https://www.epa.gov/cfl/how-energy-independence-and-security-act-2007-affects-light-bulbs

Halogen bulbs are also fine to use.  As with all bulbs, you just need to know what current will light the bulb. 

A 40W bulb is passing .33A, and a 200W bulb is passing 1.67 A at US standard wall voltage of 120V.  In a country with 240V standard, a 200W bulb would allow only 0.83A to pass. (I have no idea what bulb ratings are common in non-USA places.)

Some day I will change out my LBL socket and put in a 3-way socket with switch and suitable 3-way bulb! No I won't.   Too many other fun or needed things to do . . .

The cool thing about tungsten filaments is how their resistance rockets up at a certain temperature -- hence limiting current.

[Keppy]

I've seen varying instructions. With a lower wattage bulb, you'll see a glow pretty much whenever the amp passes current, but brighter if there's a short. With a higher wattage bulb, the bulb may not light if there is no short, so it's harder to tell if it's working. I plugged a heat gun into mine just to prove the bulb would light before trusting it.


Pretty much any available lamp in the US will at least keep you from blowing mains fuses. As said in the previous post, even a 120V/200W bulb will only pass 1.67A.