Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => AmpTools/Tech Tips => Topic started by: osing on April 08, 2008, 12:41:23 pm
-
Howdy,
I've seen some neat current limiters in the forum, and I bought some parts to make one myself. Although not necessary, I want to incorporate a master ON/OFF switch as well as a momentary ON switch (i.e. normally off) that I can use to test the lightbulb before use. Below is the planned hookup - does this look ok, or am I doing something wrong? I figure the 3A switch will basically be depressed briefly to test the bulb, and it will essentially short the receptacle into which the amp will be plugged. I don't intend to push the momentary switch when the amp is plugged in and ON, but even if that were to happen by accident, I assume there would not be any big chance of damage since the amp would simply loose power due to the short?
Does this make sense?
EDIT: I just realized I forgot to draw in the ground wires from the Socket and the 15A switch, but those would simply tie to ground with the other ground wires.
-
IMO, the on off switch is useless. I'm okay with the momentary test switch. Some people like to add a bypass switch so they don't have to unplug and plug again. I don't like to have any switches on the device.
-
Thanks LooseChange. That is a good point about the switch - a bypass switch would make a lot more sense if there is to be a switch at all.
If I'm not mistaken, the two-way light switches found in hardware stores are SPDT switches, so I could just use one of those instead (I have a box with a cutout for a switch, so I do want to put something in there :-)
I recon that this modified drawing is how I would then wire it - does this look ok?
-
I like your second design with the bypass. However I am one for a dual pole power switch with a big freaking light bulb indicating power is on.
On my setup I like to leave it all plugged in, then hit the master power switch so I can work on the circuit without having to unplug.
-
IMO, simpler is better for this device. When you start putting gadget switches like 'test the light bulb' or especially 'bypass the lightbulb' you run the risk of firing up the amp with the switch in the wrong position. You know it will happen. KISS really applies here.
-
IMO, simpler is better for this device. When you start putting gadget switches like 'test the light bulb' or especially 'bypass the lightbulb' you run the risk of firing up the amp with the switch in the wrong position. You know it will happen. KISS really applies here.
I'm with sluckey on this one.
-
And now I'm with both of you as well......after assembling the limiter yesterday per my second drawing, I realized during testing (I had a regular table lamp plugged into the outlet where the amp would normally be plugged in) that the momentary switch should not be depressed when the master switch is set to "bypass". I didn't see this when I drew the schematic, but in bypass mode, the momentary switch will simply create a short from hot to neutral and thus trip a circuit breaker.
If I were to build another limiter, I'd get rid of both switches. Going to the fuse panel to switch the circuit breaker back and resetting a bunch of electric clocks takes longer than plugging a lamp into a simple limiter (i.e. with no switches) to test the limiter bulb prior to running an amp through it :-)
Lesson learned!
-
Personally I would not use a bypass switch for fear of making myself a victim of Murphy's Law.
-
Hi friends :)
I'm not sure about your limiter usage
do you need to give less voltage to the amp in first test or other similar ??
if so
someone told me is better to put the lamp
(or better the lamps)
one for any branch of the anodic voltage
as to prevent that electrolitics can get full charge and increase dangerously the anodic voltage
sorry for bad english
Kagliostro
-
Hi friends :)
I'm not sure about your limiter usage
do you need to give less voltage to the amp in first test or other similar ??
if so
someone told me is better to put the lamp
(or better the lamps)
one for any branch of the anodic voltage
as to prevent that electrolitics can get full charge and increase dangerously the anodic voltage
sorry for bad english
Kagliostro
It is simply a light bulb in series with your load. If you turn on the amp and the lamp stays lit brightly, you know you have a short. You don't run the amp under test for long with the limiter plugged in because it's using a proportion of the voltage. It is simply a first time fire up smoke preventer.