Quick? Bulb limiter question

[surfsup]

Okay so I have my stuff to replace some Rs and retry firing up my amp tonight (hopefully) and will probably buy/build a light bulb limiter. But, I wanted to figure out what Watt bulb to use. Thinking about this simply, I have 125.2V supply AC in my wall, and the PT I have is 150mA

If I use a 25W bulb, I come up with a calculation that the bulb will allow only 199.7mA through, but that is 50mA more than my PT:

25W/125.2V=0.19968A

But since my PT is 150mA only so do I need a smaller rated bulb like a 20W which is 159mA, approximately what my PT is rated at?

[surfsup]

Okay I think I answered this, basically use a low wattage first then bring it up. for this amp, I would assume lower than 150mA then bringing it up with larger wattage bulb(s).

So starting with a 10W would be around 80mA...then a 15W then 25W would be prob the max I need with a 150mA PT yea?

[NickC]

http://tubenewbie.com/light_bulb_current_limiter.html

When first powering on a newly built amplifier, use a bulb limiter or Variac. It will keep you from destroying some very expensive parts if there is any problem with your amp. The picture shows a 75-100 watt lamp, but I typically use a 25-60 watt to start with. If there's something wrong with an amp, it will draw too much current and the light bulb will blow. But it's better to blow a light bulb then a $150 transformer.

[surfsup]

Well, I built the bulblimiter. I took a three prong cord from an existing power strip that was old and repurposed it for this. I got a Jbox with a double outlet and a switch. I wired the hot white from the three prong cord to the switch, a lead from other switch side to hot on plug1, lead from neutral plug1 to hot plug2, plug 2 neutral to the black on three prong. The green three prong lead was grounded to the green ground lug on the double outlet. This puts it all in one box. With a plug-in light socket to complete the series circuit, it works great.

Oh, you gotta break the tabs on the side of the double outlet to separate the two hots and two neutrals, very important:

[img750]http://chicagocadcam.com/ChrisHahn/sche ... imiter.jpg[/img]

[C Moore]

What kind of surfing is there in Chicago.....and how OLD is that bulb you've got there.....?

[Cygnus X1]

Nice work!

I used a deeper romex jbox for mine and was able to fit a female IEC and a fuse holder in it.

And rather than using different bulbs I use a variac.

It's already saved me a couple of times.

[img:546:364]http://img829.imageshack.us/img829/2519 ... lfront.jpg[/img]

[surfsup]

What kind of surfing is there in Chicago.....and how OLD is that bulb you've got there.....?

Been surfing or riding some board all my life (skis, snowboard, skateboard, etc)ChicagoKitesurfing.com is my website. Fun sport:

http://chicagokitesurfing.com/kiteboard ... hp?p=23480

That's me. Not bad for 42 yr old, eh? well 39 at the time. trying to stay young but its a losing battle. My 1.5yr old is already on the skateboard (kinda) and riding with me down the street on the longboard. She's already dragging her old man outside!

@Cygnus that IEC is a great idea! I see you have the plug in bulb too. Rats, thought I had a unique idea there.

[Structo]

I like to start with a 25w light bulb as well with no tubes installed.
Limits the current to less than 250ma.

Then I will generally go up in wattage with 60w, 75w.

This helps form the caps and also you will see any problems arise as the current is increased.

After I install the tubes I will try it again with a 75w bulb just to make sure nothing is wrong.

[Cygnus X1]

Thanks surfsup.
That is a bulb screwed into a two prong plug-in socket.

IEC is nice, but even more important is having that fuseholder there.
2A slo-blo, it's extra insurance.

And the giant screw style terminal block gives all kinds of options for breadboarding.
Apart from that, it's the same as yours.

[showsii]

Quick question involving the Bulb limiter..


If mine is glowing with the amp on and the stand by engaged, does this mean I have problems?

I am using a 40 watt bulb, its a dim glow.


Thanks

Ian

[brewdude]

It's been a while since I used mine, but I think the bulb should shine brightly for a moment and then quickly fade to a steady dim glow.

[Masco]

Get two switches. One for on/off and one to bypass the bulb. Also, multiple bulb sockets in parallel w/ the series bulb will let you add/subtract wattage. Just screw/unscrew as needed, they don't usually get too hot to touch (well, the souldn't if everything is working ok w/ the amp under test).

[C Moore]

Is there a definitive explanation/theory of what/when to use different watt bulbs in a limiter.?
I built one when I had a stubborn "fuse blowing" problem, and it helped. It saved on fuses until I found the problem. But I never understood why I should use one wattage bulb over another.
Thank You

[C Moore]

Is there a definitive explanation/theory of what/when to use different watt bulbs in a limiter.?
I built one when I had a stubborn "fuse blowing" problem, and it helped. It saved on fuses until I found the problem. But I never understood why I should use one wattage bulb over another.
Thank You

[surfsup]

One for on/off and one to bypass the bulb.

Great idea but I can see the future..."why'd my amp catch fire? Ahhhdamn I forgot to engage the bulb!!!"