Pilot Lamp Draws Too Much?

CarlosT · 27th December 2006, 04:09 PM

Interesting experience I had was related to a pilot light...

I was initially wiring a pilot light off the DC power V+ and common. My little 90VA 20V + 20V was putting out about 31V + 31V under no load after rectification. I had a Sylvania old school pilot light with a red jewel lens with a 28V 28MB bulb. Well...when I hooked up the pilot light, don't you know that the voltage on that leg of the DC power dropped to like 25V. I got worried about it and decided to power the pilot light right off the AC 110V (of course with an appropriate 120V 120MB bulb). Did I need to worry about this? I didn't wanna create some kinda imbalance between the V+ and the V- voltages but maybe this was just the PSU settling in on the "under load regulation" terminal voltage values and I had nothing to worry about.

Thoughts? Comments? Which way would you go...28V DC or 115V AC?

I_Forgot · 27th December 2006, 04:21 PM

It is not unusual for an unregulated power supply voltage to drop a few volts when even a relatively small load is connected to the supply (in this case, a 40 mA bulb). I wouldn't worry about it because the amplifier will prove to be a much bigger load. Connect the amp to the supply and check the voltage on both sides of the supply and I think you'll find them within a few 1/10ths of a volt.

If you're really worried about it, put a matching bulb on the other half of the supply, or switch to LEDs.

I_F

27th December 2006, 04:09 PM	#1
CarlosT diyAudio Member Join Date: Oct 2006	Pilot Lamp Draws Too Much? Interesting experience I had was related to a pilot light... I was initially wiring a pilot light off the DC power V+ and common. My little 90VA 20V + 20V was putting out about 31V + 31V under no load after rectification. I had a Sylvania old school pilot light with a red jewel lens with a 28V 28MB bulb. Well...when I hooked up the pilot light, don't you know that the voltage on that leg of the DC power dropped to like 25V. I got worried about it and decided to power the pilot light right off the AC 110V (of course with an appropriate 120V 120MB bulb). Did I need to worry about this? I didn't wanna create some kinda imbalance between the V+ and the V- voltages but maybe this was just the PSU settling in on the "under load regulation" terminal voltage values and I had nothing to worry about. Thoughts? Comments? Which way would you go...28V DC or 115V AC?

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27th December 2006, 04:21 PM	#2
I_Forgot diyAudio Member Join Date: Jan 2005 Location: Phoenix, Az.	It is not unusual for an unregulated power supply voltage to drop a few volts when even a relatively small load is connected to the supply (in this case, a 40 mA bulb). I wouldn't worry about it because the amplifier will prove to be a much bigger load. Connect the amp to the supply and check the voltage on both sides of the supply and I think you'll find them within a few 1/10ths of a volt. If you're really worried about it, put a matching bulb on the other half of the supply, or switch to LEDs. I_F

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