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LED to replace 6.3v pilot lamp

Discussion in 'Shock Brother's DIY Amps' started by jhundt, Dec 28, 2014.

  1. jhundt

    jhundt Doctor of Teleocity

    Age:
    64
    Mar 23, 2003
    Netherlands
    bparnell57 - thanks for the suggestion. I just went and looked at the schematic for the Champion 600, and there was an LED pilot lamp wired exactly as bwacke and gnobuddy have been teaching me.

    but I'm curious - why do you hate these lamps?
     

  2. Gnobuddy

    Gnobuddy Friend of Leo's

    Sep 15, 2010
    British Columbia
    I'm curious about that too!

    The Super Champ XD also has an LED power indicator light. I don't recall if it's run off the heater power, or one of the low-voltage DC supply rails in that amp. Being half solid-state, there are +/- 12V rails, and I think there is also a lower (+5V, maybe) voltage used for some of the digital chips in the amp.

    I think there is something to be said for going backwards in technology to a very old type of lamp: a neon bulb. These can be wired (with a series resistor, like an LED, but chosen for much lower current - usually a milliamp or less) direct across the B+ voltage in the amp.

    So the ancient neon bulb is a very good safety indicator for anyone contemplating working on an amp. If heater power fails for some reason (say a bad winding on the power transformer) an LED or jewel lamp powered by the heater supply would go out - even if the full high-voltage B+ rail was still live at +400 volts or whatever.

    Neon bulbs are very dim, though, and hard to find these days. I may settle for putting one inside the amp I'm building, just as a safety indicator.

    -Gnobuddy
     

  3. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    For an inside the chassis safety 'hot amp' indicator I'd recommend a small 120v light tapped at the fuse and power cord neutral wire.
     

  4. Alamo

    Alamo Doctor of Teleocity Silver Supporter

    Nov 15, 2006
    Berlin
    I'd wager that a simple LED light just doesn't look as cool as Jewel pilot light assy. I wouldn't mind if there was an LED hiding inside but its gotta have a jewel thingy :cool:
     

    Attached Files:


  5. bparnell57

    bparnell57 Poster Extraordinaire

    Feb 10, 2014
    Philadelphia, PA

    The Champ 600 and Excelsior I have both have LED pilots, but they don't look right and I can't change the color or even swap to a correct regular pilot light without drilling.... They're just cheap chrome plastic and I don't like it....
     

  6. bparnell57

    bparnell57 Poster Extraordinaire

    Feb 10, 2014
    Philadelphia, PA

    Also, RadioShack sells square Marshall type neon indicators in multiple colors at okay prices...
     

  7. Gnobuddy

    Gnobuddy Friend of Leo's

    Sep 15, 2010
    British Columbia
    Nice idea!

    How small do low-wattage 120V bulbs get? The smallest ones I can think of are the little night-light bulbs, which are still a lot bigger than an NE2 neon bulb (but a lot easier to find these days).

    -Gnobuddy
     

  8. Gnobuddy

    Gnobuddy Friend of Leo's

    Sep 15, 2010
    British Columbia
    Thanks for the tip!

    I'm amazed RadioShack is still in business, they've had one foot in the grave and the other on a banana peel for years now.

    It's probably not a good idea to name your brand after any single electronic product - how much resonance does the word "radio" have for most people these days?

    -Gnobuddy
     

  9. Newt522

    Newt522 TDPRI Member

    63
    Jan 24, 2015
    South Carolina
    Neon Lamps

    I liked to use 110v neon lamps. It's been around 10 years; I think I got them from Radio Shack. Use amber for standby and green for "Go". Used DPST toggles or a rotary switch. The lamps were around 10ma, I think, and glowed nicely.

    RatShack shows only a red one now, for $1.99.
     

    Attached Files:


  10. Gnobuddy

    Gnobuddy Friend of Leo's

    Sep 15, 2010
    British Columbia
    Neon bulbs seem to have been a victim of the recent low lead / restriction of hazardous substances (RoHS) regulations. They are much harder to find these days.

    The same regulations have eliminated cadmium sulphide light dependent resistors (LDR's), the kind used in many guitar compressor and tremolo pedals. Cadmium is pretty toxic, so the CDS LDR's are now basically extinct, unless you stumble across an old stash of them somewhere.

    It's getting harder to buy leaded solder, too. I'm glad they're getting lead out of the environment, but lead-free solder is quite hard to work with in the hobbyist environment. It's very much less forgiving during soldering.

    -Gnobuddy
     

  11. papaschtroumpf

    papaschtroumpf Tele-Holic

    573
    Nov 24, 2015
    Colorado
    Anyone knows where to find screw type (not bayonet type) 6.3V either bulbs or preferably LED replacement?
    My Monoprice 15W takes the screw in type.
     

  12. muscmp

    muscmp Tele-Holic

    831
    Jul 1, 2008
    california
    the thread gives places to get the led. otherwise you may google your particulars.

    play music!
     

  13. DCW74

    DCW74 TDPRI Member

    Age:
    44
    66
    Sep 11, 2018
    Columbus, OH
    I just measured my heater voltage at startup and after warmup, then looked at the maximum and regular operating forward voltage voltage of the LED I wanted to use. That gave me the range I needed. Then I used an online calculator to figure out my dropping resistor.

    You want to take a cold start voltage reading because a cold filament passes more current.
     

  14. Alamo

    Alamo Doctor of Teleocity Silver Supporter

    Nov 15, 2006
    Berlin
    I had an intermittent pilot light in my TweedTone Vibrolux clone. sometimes it was on, then it's off.
    that's the reason I recently left the amp on ...over a whole day and some.
    it seemingly didn't hurt the amp, only the pilot light now stays on.
    what's up with that? magic?

    22-DSCN1895.JPG
     

  15. jhundt

    jhundt Doctor of Teleocity

    Age:
    64
    Mar 23, 2003
    Netherlands
    that's funny... I built a Mojo kit 5F11 Vibrolux. The kit was excellent (it's the only kit amp I have built), except the pilot lamp was intermittent... the only bad component in the box.

    BTW I can't even tell you how many times I have left my amp on overnight. Or even for several days...
     

  16. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    Another method is to just use another led in parallel, reversed. That way you get light on both cycles of the ac, and the leds protect each other while sharing the single resistor.
     

  17. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    I used neons a lot back in the old days, they were cool... remember the old neon pocket voltage testers?

    For an inside-the-amp indicator though, both neons and incandescents are too unreliable, burning out suddenly... I’d rather use leds for their ultra reliability, especially when you run them at 1/3 or 1/4 recommended current, which I always do, mainly because they are too dazzlingly bright even at half current.
     

  18. jhundt

    jhundt Doctor of Teleocity

    Age:
    64
    Mar 23, 2003
    Netherlands
    neon voltage tester? Is that like a little screwdriver that you stick in the socket, then touch your finger to the little button and see if the bulb lights? I keep one of those in the pocket of my work apron when I'm painting houses.
     
    Rich_S likes this.

  19. rogb

    rogb Tele-Holic

    828
    Jan 3, 2012
    London, England
    This is how Dumble did the LED pilot - AC 6.3 heater fed into the resistor and back into diode - works just fine.
    diode.jpg
     

  20. Old Tele man

    Old Tele man Friend of Leo's

    May 10, 2017
    Tucson, AZ
    I have a blue LED replacement #47 bulb in my SR.
     

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