Replacing Jewel bulbs with led

[diydidi]

Hi.
Is it ok to replace the power indicator bulbs in say Fender amps with an led?
I was thinking of using a diode and resistor soldered directly to the socket where the bulb use to be. I don't even think a cap is necessary.
Will it influence the Filament voltages in a bad way?
Also, what colour LED would be suggested? I suppose white would work for most coloured jewels...

[Leo_Gnardo]

By coincidence I just did this 2 days ago in an early 70's vintage Phase Linear 400 solid state amp. There's a separate PT winding just to light up the 8 meter lamps. I used a 1N4001 rectifier, 1000 uF 10V cap, 10 ohm current limiting resistor and 8 hi brightness blue LED's. The meters now light up sexy blue like a McIntosh instead of vapid white like they used to. Everybody that sees it has a "wow" reaction. Hey it's just a lowly Flame Linear but looks super groovy now. I'm sure you can do similarly in a Fender or any other amp with a 6.3 VAC pilot lamp & jewel. Modern LEDs are tough and may even be able to light up right off a 6.3V line but I would recommend a current limiting resistor & rectifier anyway. The current drawn for LED will be so low it should not induce any noise into the filament line that may translate to buzz in the audio. White thru a color jewel should look cool. I've been considering putting color LED behind a milk-white jewel. Some manufacturers have been using an LED behind a traditional looking jewel for a over a decade now. How they power the LED, whoops I havent' been paying attention. Easy enough to grab a couple milliamps from a low voltage supply for op amps or relays.

[tedmich]

what Leo said^
my $0.02, modern LEDs can be crazy bright and an indicator you can read under in a darkened room is obnoxious, so I often have to drop substantial current before they approximate the soft glow of old neon or filament bulbs.

[PeanutNore]

You can run an LED off basically anything. LED Christmas lights run off household 120VAC. Figure out the max current of your LED, subtract the voltage drops of the LED (and rectifier if you choose to use one, good idea with a high voltage AC supply) from your supply voltage and choose a resistor to give you that much current or less, to taste.

[mhuss]

One caveat, the peak reverse voltage for LEDs is pretty low, so it doesn't hurt to add a 1N400x diode in series unless your source voltage is really low.