Amp jewel light in a pedal?

[HeavyFog]

Anyone done this before? Putting together a dual valvecaster (12v) and i since IL be using fender style amp knobs i figured i should try using a jewel pilot light instead of a regular red led. I know these usually run off 6.3vAC but could i run it off 12vDC with a current limiting resistor like i would for a regular LED or would i have to try to mount a regular LED under the lens? If so what value resistor would be used?

[digi2t]

You can buy the jewel itself, with a mounting nut, and use an LED. As for the resistor it all depends on the LED. How bright do you want it? How much current do you want to sacrifice for it? Anywhere between 680 ohms, and 4.7K is generally the range I work in. Plenty of info on the net to help you figure out which resistor to use.

[HeavyFog]

I was thinking about using the actual bulb that would typically goes behind the pilot light. I'm used to using regular LEDs (i almost always use a 1.5k resistor) so i could definitely do it like that but i'm curious to see if using the bulb the lens is meant for (same one most amps use) is possible or not. The description for the bulb just says 6.3v so i'm not certain if it would work.

[rutabaga bob]

If you run a 6.3. volt incandescent bulb off 12 volts without a resistor to drop that voltage, it'll fry in a heartbeat.

I've got a jewel from an old piece of machinery that's about 1" across...have thought about trying to find a use for it in a pedal! 

[HeavyFog]

Maybe a 1.5k-3k resistor would be enough to drop 12vDC down enough not to fry the bulb? If so it should work just fine as an on/off status indicator connected the same way to the bypass switch as any other regular led would. I don't think these bulbs too need much current either.

[thermionix]

Going completely from memory, I think the #47 bulb that is typically used in Fender amp pilot lights is 6.3V 125mA.  Kinda high current for a battery operated pedal.  I second the LED/jewel idea.  It looks fine, I have an amp here for repair now that is done that way, you wouldn't know it wasn't a bulb from the outside.

[thermionix]

Correction, 150mA.

[amptramp]

Here is a page for common bayonet and screw-base bulbs:

http://www.nostalgiaair.org/References/lamps/

But you could use a LED behind the jewel, you won't see much of a difference.

[davent]

An ultrabrite  led you can run at less then 1mA and be plenty bright, you just glue the led with clear epoxy into the jewel. See if you can find and check out pedals by Darron and Basic Audio.

dave

[LightSoundGeometry]

I still havent tried the JB weld yet, got three  boxes holed up to patch or attempt to patch, but I filled a misdrilled hole with a 8mm and a 10mm before and its too much ..the led is just too much light and is a hindrance imho ..would not recommend it unless you fancy staring into lights

[davent]

I still havent tried the JB weld yet, got three  boxes holed up to patch or attempt to patch, but I filled a misdrilled hole with a 8mm and a 10mm before and its too much ..the led is just too much light and is a hindrance imho ..would not recommend it unless you fancy staring into lights

Just keep increasing the current limiting resistor until the amount of light is to your liking, there is no correct value, it just needs to be big enough to meet the max allowable current (20mA) which and with an ultrabrite, max is way too bright.  Try it at 1mA or even less.

dave

[EBK]

I still havent tried the JB weld yet, got three  boxes holed up to patch or attempt to patch, but I filled a misdrilled hole with a 8mm and a 10mm before and its too much ..the led is just too much light and is a hindrance imho ..would not recommend it unless you fancy staring into lights

Just keep increasing the current limiting resistor until the amount of light is to your liking, there is no correct value, it just needs to be big enough to meet the max allowable current (20mA) which and with an ultrabrite, max is way too bright.  Try it at 1mA or even less.

dave

Good Lord, no!  We're dilated to 10mm already!  We need to get that LED delivered now and sew up any damage with JB Weld, stat! 

[PRR]

47 Ohms, 2W

[deadastronaut]

I bought 10mm warm white leds just for this...(those grey white ones are horrible)

i have a few jewels too... 

warm white actually look, behave like a bulb...

[HeavyFog]

IL give the bulb a try to see if it works and if it doesn't IL use an 8mm LED to see how that works. Still not sure what size resistor to use so IL try a few values between 1k-3k to see what gets the bulb bright without killing it. I'm not worried about the higher current draw since i wont be using a 12 wall wart for power instead of a battery. I wonder if i could get the bulb to fade in and out when turned on and off.

[greaser_au]

Hey, HF! 
You haven't told us which socket you have to use?   
In any event, 12.6V is a bog-standard auto lamp (as was 6.3V in ancient times...  why are 6V valves 6.3V? - because a fully charged lead-acid cell is about 2.1V...).   Surely you should have no trouble finding one of those nearby?  (not intended to come off as flip, this is a serious suggestion).

If a bayonet or SES lamp is hard to find, what about a wedge? Maybe look for a 12V W5W,  these things flood the dashboards of just about every car since the 1970's and are the same size as a Fender pilot light...       The smaller 1.2CP T-1-3/4 are also an option if you can choose your socket...

I'm a long way from any kind of authority, but I'd take DA's (and bigclivedotcom's*) suggestion and go the warm white LED

good luck
david

* bigclivedotcom - youtube channel

EDIT:   MES (minature edison screw, not SES, sorry)

[HeavyFog]

Il be using these sockets and #47 bulbs from mojotone

http://www.mojotone.com/amp-parts/PilotLights_1/Pilot-Light-Assembly-Jewels-Sold-Separately

Since il be using a larger enclosure i don't mind the larger size a long as the enclosure has enough depth for the tall socket.
I should pick up a 12BH7 tube while i'm at it. They sounds really good in a valvecaster!

[greaser_au]

to go with your 12BH7,  I reckon you'd  want a GM #9428049     14V, 0.08A   T3-1/4  15,000 Hour  bayonet (or BA-9S for us metric types)         #756     (are cheaper than a #47 at bulbtown, too)

david

[HeavyFog]

For now i think IL stick with the #47 bulb since i can get get everything at once from mojotone but if it works really well i might give the longer lasting one a try. I might try some other tubes like a 12AT7 in there as well. Either that or the 12BH7.

[amptramp]

For now i think IL stick with the #47 bulb since i can get get everything at once from mojotone but if it works really well i might give the longer lasting one a try. I might try some other tubes like a 12AT7 in there as well. Either that or the 12BH7.

Keep in mind the 12BH7 requires twice the heater current of a 12AT7 / 12AX7 / 12AU7.