lamp limiter with switch

[John]

Hi fellas, I want to build a limiter that I can just switch back and forth between limited and not limited. I don't see why this wouldn't work correctly, but also know that I'd better ask first!

[Willabe]

I have mine wired that way. Except that I have a duplex outlet. Light bulb/lamp goes in 1 socket, device under test/limit goes into the other. I took a red marker and colored the "hot" outlet socket. Flip the switch and full power. It's in 1 of G. Weber's books. Makes it easier cause you don't have to keep plugging/unplugging the amp.


                  Merry Christmas,     Brad          

[stratele52]

This good John.

Myself I build Weber' s one.

[sluckey]

That works fine. Another very simple way to bypass the light bulb is to put a SPST switch parallel to the light bulb.

[birt]

i'm about to build one too. except i will use 2 switches, one to turn on the power and the second to bypass the bulb. or maybe even a rotary switch so the chronology is always the same.

[stratele52]

That works fine. Another very simple way to bypass the light bulb is to put a SPST switch parallel to the light bulb.

That's what John's shematic show no ? .

For myself I think is more safe to use this limiter with no bypass switch.  If I need to plugg the amp in this current limiter I want to be sure is not in by pass mode.
When I need full power I plug in the wall outlet.

[G._Hoffman]

Honestly, I wouldn't WANT a switch to bypass the limiter.  It's there as a safety precaution, and I don't want any chance of accidentally turning things on without it when I want it there, which is all too easy to do if there is a switch.  It is easier enough to unplug and replug, when you need to, and the slight bit of hassle keeps you from making a mistake.


Gabriel

[John]

Thanks for the replies! I use the limiter every time I re-solder anything, so I'm plugging/unplugging a lot.

[sluckey]

That's what John's shematic show no ?

It's not quite the same. John shows a SPDT switch and I show a SPST switch. A subtle difference that accomplishes the same function.

I agree with you and Gabriel... I would not want a limiter bypass switch. Once you put a bypass switch on it, you introduce the possibility of having the switch in the wrong position at the wrong time. KISS factor. A switch that bypasses the amp and puts the light bulb at full brightness would be more useful IMO. This would allow you to set a reference in your mind about how bright the bulb will be at full brightness (dead short amp).

This workbench gadget is a one trick pony. It allows you to connect a light bulb in SERIES with your amp. It will allow you to determine if your amp is drawing excessive current due to a shorted PT or filter caps, etc., without blowing fuses or smoking valuable components such as a PT. A dead short on the primary side of the PT will cause the bulb to glow at full brightness. Partial shorts or a short on the secondary side of the PT will show some increased level of brightness. A properly working amp will cause the bulb to glow fairly bright when first turned on, but will fade to a dimmer glow as the amp warms up.

Once you have confidence that there is no high current drain from your amp, you should remove this gadget. It has served it's purpose.

Here's a pic of the SPST bypass switch. Again, I don't recommend this switch...

[jjasilli]

Honestly, I wouldn't WANT a switch to bypass the limiter.  It's there as a safety precaution, and I don't want any chance of accidentally turning things on without it when I want it there, which is all too easy to do if there is a switch.  It is easier enough to unplug and replug, when you need to, and the slight bit of hassle keeps you from making a mistake.

Gabriel

Ditto (in homage to Murphy's law)

[John]

Hmmm.... the tribe has spoken, no switch on the island! Thanks for the replies and advice.

[six el six]

My experience has been that I often forget that I have the lamp/bulb in the circuit and I forget to switch it out.

On amps that need a lot of power, they often won't make a sound with the limiter on and they often don't even light up.

It also takes a while to get used to how bright the bulb should be lit.

[LooseChange]

I use two different bulbs with the limiter. A 60 watt and a 150 watt. On higher powered amps I use the 150w. If an amp draws a lot of current by design, the 60 watt bulb will burn pretty bright.
I also use them in succession, sort of like a variac.
You can learn a lot from the bulb... respect the bulb. :-)

[eleventeen]

I respect both of them.