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 Friend of Leo's

    Posts:
    2,150
    Joined:
    Jul 28, 2012
    Location:
    age 8
    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 Poster Extraordinaire

    Posts:
    5,276
    Joined:
    May 5, 2015
    Location:
    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 Poster Extraordinaire

    Posts:
    5,192
    Joined:
    Jan 1, 2013
    Location:
    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 Poster Extraordinaire

    Posts:
    5,276
    Joined:
    May 5, 2015
    Location:
    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 Ad Free Member

    Age:
    63
    Posts:
    17,371
    Joined:
    Jul 18, 2010
    Location:
    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.
     
    tubegeek likes this.
  6. King Fan

    King Fan Poster Extraordinaire

    Posts:
    5,192
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    LOL, yep, I almost always start to measure voltages on the limiter during startup.... Forehead has calluses.
     
    Commodore 64, Fiat_cc and moosie like this.
  7. cap47

    cap47 Tele-Holic

    Posts:
    531
    Joined:
    Jul 27, 2014
    Location:
    bushnell, fl
    100 W works fine !

    [​IMG]
     
    King Fan likes this.
  8. dav70ita

    dav70ita TDPRI Member

    Age:
    49
    Posts:
    38
    Joined:
    May 2, 2018
    Location:
    Madrid
    Hi,

    What’s the bulb amperage to be used on a bulb current limiter for a European 5e3 amp working with 230V.

    Should it be half the amperage used for a 120V 5e3 amp? What I mean is that, if a 150W bulb must be used on a 120V 5e3 amp, we should use 75W bulb on a 240V 5e3 amp. Is that correct?
     
  9. Bendyha

    Bendyha Friend of Leo's Silver Supporter

    Posts:
    2,433
    Joined:
    Mar 26, 2014
    Location:
    Northern Germany
    From National Radio News 1936 -08 -09

    upload_2018-7-25_22-34-42.png
    upload_2018-7-25_22-35-41.png

    upload_2018-7-25_22-37-31.png upload_2018-7-25_22-38-26.png


    and here is something like one, that is from 1912 (not the bulb)

    upload_2018-7-25_22-39-54.png
     
    SSL9000J likes this.
  10. telex76

    telex76 Doctor of Teleocity Ad Free Member

    Age:
    69
    Posts:
    16,116
    Joined:
    Jun 24, 2006
    Location:
    Fort Worth,Tx.
    I use 100 watt. I've got one I use and a spare. Hope they don't get broken in my lifetime, cause I don't see them for sale anymore.
     
  11. moosie

    moosie Doctor of Teleocity Ad Free Member

    Age:
    63
    Posts:
    17,371
    Joined:
    Jul 18, 2010
    Location:
    Western Connecticut
    telex76, magic smoke and mndean like this.
  12. Thomthom098

    Thomthom098 TDPRI Member

    Age:
    47
    Posts:
    60
    Joined:
    Apr 7, 2020
    Location:
    Monaco
    Halogens are still commonly found, guess they would have similar characteristics as old incandescent filaments which they have just as well - and would do the job no ?:
    Screenshot_20200528-205655_Chrome.jpg
     
  13. moosie

    moosie Doctor of Teleocity Ad Free Member

    Age:
    63
    Posts:
    17,371
    Joined:
    Jul 18, 2010
    Location:
    Western Connecticut
  14. tubegeek

    tubegeek Tele-Afflicted

    Age:
    59
    Posts:
    1,824
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    That's supposed to be your connection to the load side. Connect the line side to the nub on the inside of the socket. For safety.
     
    Last edited: May 28, 2020
    sds1 likes this.
  15. tubegeek

    tubegeek Tele-Afflicted

    Age:
    59
    Posts:
    1,824
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    Here's one that started life as a glass-fuse fusebox for a small apartment. I use a 40W bulb for initial check, and a higher-wattage bulb once I think it's working OK.
    20200528_173121.jpg

    One poster above was asking if a higher wattage bulb would survive the shock of a faulty amp better. You can't get faultier than a dead short to the live wire which is what the bulb is designed to do all day long.

    Lower wattage limits more aggressively, higher wattage behaves more like just plugging the amp straight in.
     
  16. sds1

    sds1 Tele-Afflicted

    Age:
    43
    Posts:
    1,404
    Joined:
    May 4, 2017
    Location:
    Orlando, FL, USA
    Haha 3 years later I still use that limiter wired backwards I guess. It never shocked me again.
     
    tubegeek likes this.
  17. SacDAve

    SacDAve Poster Extraordinaire Silver Supporter

    Age:
    68
    Posts:
    7,088
    Joined:
    Dec 23, 2009
    Location:
    Rocklin Ca.
    Don't use an LED light .........thrust me :cry:
     
    tubegeek likes this.
  18. Greenmachine

    Greenmachine Tele-Holic

    Posts:
    807
    Joined:
    Nov 28, 2011
    Location:
    New Jersey
    100w
     
  19. King Fan

    King Fan Poster Extraordinaire

    Posts:
    5,192
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    I always assumed / heard the bulb had to be incandescent. Yes no maybe but except?
     
  20. Andy B

    Andy B Friend of Leo's Silver Supporter

    Posts:
    2,291
    Joined:
    Mar 16, 2003
    Location:
    Castle Rock, Colorado
    I‘ve used 100W bulbs for years in my limiters. The 72W equivalents are fine also.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.