I recently picked up a Citation Eleven preamp in a trade, and I need to replace the pilot lamp. The stock lamp is rated 10V .20ma. Now this might be a foolish question, but can I replace the lamp with an LED? I have an LED that fits perfectly, but it is rated 12V .20ma. I really like this preamp and do not want to screw it up in any way.

Any assistance is much appreciated, I want to get done with the Citation so I can move on to the power amp (not an HK, but a very very nice Sonogy Cantata, I plan to pair them up with either Allison Threes or Polk Monitor 7b's).

I recently picked up a Citation Eleven preamp in a trade, and I need to replace the pilot lamp. The stock lamp is rated 10V .20ma. Now this might be a foolish question, but can I replace the lamp with an LED? I have an LED that fits perfectly, but it is rated 12V .20ma. I really like this preamp and do not want to screw it up in any way.

Any assistance is much appreciated, I want to get done with the Citation so I can move on to the power amp (not an HK, but a very very nice Sonogy Cantata, I plan to pair them up with either Allison Threes or Polk Monitor 7b's).
I see no issue, a 12v LED works fine at 10v, make sure you use an LED that accepts AC voltage, many of the newer ones do, Dave.

Thank you very much for that info, that helps a great deal! Is there any way to easily tell if the one I have will accept AC? It is just a red LED assembly I picked up at the Shack for a buck and change, it fits perfectly into the slot I have for it, but I am unsure if it will accept AC. It makes no mention of that on the packaging, anyways. This job would be substantially easier if this will just swap right in for the stock lamp.

No LED will deal with an AC signal...you need a blocking diode.

And I've never heard of a 12V LED.

This one seems to be 12V, it says on the packaging "Forward (supply) voltage: 12.0". It also says it has a built-in resistor, whatever that may accomplish. Well, even if it won't work for my desired application, I really only bought it for the red lens assembly, planning to use it with a standard lamp. But it just would have been so much easier if I could simply use the LED instead of hacking something together! I may not be the brightest guy on the block but hey, at least I know enough to ask the folks here who actually know these things before diving in.

Thanks very much!

I appreciate the input, I am really looking forward to getting this all ready to roll.

That voltage is a LOT more than 10 volts, it is a 10v 20mA incandescent lamp with a 3300 ohm 3 watt resistor.

It is at least 50 volts, and hk uses a 1000 uF 100v cap as the main cap.

I would have to see the Radio Shack part (what is the number?) but I'm 99% sure that if you just drop it in, you will get a bright flash and then nothing at all.

It will take a bit of unravelling to figure out what will work. No quick answers on this one (except for the NO), sorry.
I suspect the voltage on C6 is about 75 volts...

It also says it has a built-in resistor, whatever that may accomplish.The resistor sets the current to 20mA when the supply is 12V. LED's don't generally come with built-in resistors. Read post #3 here: http://www.audiokarma.org/forums/showthread.php?t=119597

The easiest thing to do is to power the LED from the 30VDC supply...makes things a lot easier. You don't have to have a blocking diode with a DC supply, and all you need to do is calculate the value for the current limit resistor.

The part I have is actually an LED, a plastic lens assembly, and wire leads with a built-in resistor. However, I only really bought it for the red plastic lens piece, but then I just figured, if it was realistic to put the whole thing in there in place of the lamp...

I think I'm just going to hack the lens cover off of the LED and use it with the stock lamp. That's not a bad solution in any event, I think I can make it look good. What got me started on this idea in the first place was the search for a suitable red plastic piece, and I do have that now. Made for some interesting discussion though!

No LED will deal with an AC signal...you need a blocking diode.

And I've never heard of a 12V LED.

Glen,
The AC versions have a built-in diode, most likely a 1N-4148, Dave.

12/24V LED (http://www.mcminone.com/product.asp?catalog%5Fname=MCMProducts&category%5Fname=3831255&product%5Fid=25%2D3425)

Well...that's an assembly, not an LED. Looks like you get an LED, a resistor, and a blocking diode. And you're limited to 12 or 24V (but you can certainly use the little buggars on a lower voltage).

I know exactly what you have and have used the identical part in numerous Citation 11 preamps. It will work fine and looks better than the original red lens HK used.

DH

The part I have is actually an LED, a plastic lens assembly, and wire leads with a built-in resistor. However, I only really bought it for the red plastic lens piece, but then I just figured, if it was realistic to put the whole thing in there in place of the lamp...

I think I'm just going to hack the lens cover off of the LED and use it with the stock lamp. That's not a bad solution in any event, I think I can make it look good. What got me started on this idea in the first place was the search for a suitable red plastic piece, and I do have that now. Made for some interesting discussion though!