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Would a low voltage DC LED used as a power indicator light appreciably affect the circuit properties or battery life?
Thanks (I got one coming!)
Joel
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Replace the power switch with a DPDT switch. The LED and a battery can be turned on with the second pole.
Remember, YOU are the only one who needs to be happy with the sound of your system
Grainger Morrison
There Is Only One (Grainger Morrison, it seems)
The power switch is a double-pole switch. It switches both (floating, independent) filament batteries. There is no high voltage switch - when the filaments are cold, no current is drawn. (This is the way battery radios from the forties often worked.)
Edits: 09/24/09
I guess the previous post should read triple pole double throw switch.
Remember, YOU are the only one who needs to be happy with the sound of your system
Grainger Morrison
There Is Only One (Grainger Morrison, it seems)
That's also a good way to do it. That way you aren't messing with the original circuit.
Thanks
The heater supply is dual 1.5v (they float so each tube needs its own). That's not enough voltage to power an LED.
The high voltage supply is not switched, so an LED across it would drain the battery and stay lit until the battery died. Not a good idea! If you added a switch, then even 1mA drain (a fairly dim LED) will still reduce battery life 20%.
However ... just put the LED in series with the high voltage supply! That way it will draw 4mA when operating, and only lose 1.5-2v out of the 36 volt nominal power supply.
no dropping resister needed?
Nope. Just solder in the LED and you're done.
Thanks
It's hard to think 36vdc as high voltage!
How about 12v? If you've ever had your hot sweaty body resting on a fender sanded down to bare metal while you worked on the engine and your elbow hit the positive battery terminal, you'd know what I mean. :-) I can tell you it is very unpleasant to get a shock that enters your elbow and exits your solar plexus. No fun at all, but of course we are talking about a huge available current with a car battery.
-- Jim
I've experienced the car battery "burn" as well. No fun!
You could put an LED in, but I would do it across the series string of 9V batteries. Try a 45k resistor in series with the LED. (1/2 watt)
One LED won't draw much current, won't make a noticeable change in battery life. You could put it across the heater supply, 3V and use an appropriate dropping resistor.
Remember, YOU are the only one who needs to be happy with the sound of your system
Grainger Morrison
There Is Only One (Grainger Morrison, it seems)
Thanks, I'll try it.
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