Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

How big a bulb for current limiter

Discussion in 'Shock Brother's DIY Amps' started by nutt, Oct 27, 2017.

  1. 2 Headed Goat

    2 Headed Goat Tele-Holic

    508
    Jul 28, 2012
    Here & Now
    I've used a 150W bulb when working on old Fender amps. Personally I wouldn't use any lower than this wattage.
     

  2. JuneauMike

    JuneauMike Tele-Holic

    925
    May 5, 2015
    Alaska
    I used a 150W bulb for my 5F1 build and the bulb didn't even wake up when the amp turned on. I swapped out a 65W bulb and got a nice dull glow out of it. I think I like having some reaction from the bulb just to confirm that its part of the equation. But I assume the larger the bulb the bigger punch it can take if you've got a problem inside the amp.
     
    Bill Moore and King Fan like this.

  3. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Excellent, Mike. My simple-minded notion is the bulb does several things -- limits current, glows brightly with a short, and may glow dully to indicate a working circuit, but only if it glows in the range of the amp's (working / testing) current draw. (Experts, yes / no?)

    Matching the bulb wattage to the amp's power consumption seems logical. Of course functions 1 and 2 are the real key -- yeah, I've seen the bright glow once. :)
     

  4. JuneauMike

    JuneauMike Tele-Holic

    925
    May 5, 2015
    Alaska
    This has been my first scratch build and second amp build so I don't have full confidence in what I'm doing. I frankly wasn't sure the light bulb limiter was working correctly with the 150 watt bulb. So the dull glow was just assurance to me that yes, it was wired in series correctly and it is working. I also used a light bulb plug adapter in my limiter build which gave me the ability to plug straight into an outlet and test that the bulb was still working before firing up the amp. That's a pro tip from an amateur, ha.
     
    King Fan likes this.

  5. moosie

    moosie Doctor of Teleocity Silver Supporter

    Age:
    60
    Jul 18, 2010
    Western Connecticut
    You can see that the limiter is working, with a large bulb, by measuring plate current. Get very confused, than slap your forehead and start it back up without the limiter. D'oh.
     

  6. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    LOL, yep, I almost always start to measure voltages on the limiter during startup.... Forehead has calluses.
     
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  7. cap47

    cap47 Tele-Meister Silver Supporter

    397
    Jul 27, 2014
    bushnell, fl
    100 W works fine !

    [​IMG]
     
    King Fan likes this.

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