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The Acoustic Club

Discussion in 'Amps and Cabs [BG]' started by The Owl, Jun 17, 2008.


  1. JacklegBass

    JacklegBass

    Jul 4, 2004
    That looks pretty good to me. I notice that in addition to eliminating the death cap from the common terminal of the GND/REV switch you would also eliminate the .047 cap across the terminals of the ON/OFF switch. It's been a long time, I think I might have left that one in place thinking it's purpose is to ease the burden on the switch contacts at turn-on and minimize pitting. The power switch is pretty light duty and a bear to replace. If the GND/REV switch shorts it's going to light up the chassis, but if the power switch cap shorts it seems the worst that would happen would be that the amp never turns off. Anyhow, what you have sketched out should work.
     
    FranF likes this.
  2. chadds

    chadds

    Mar 18, 2000
    What?
     
    Sorado71 likes this.
  3. Why would you want to remove the cap across the power switch? It's beneficial to protecting the switch contacts.
     
    FranF and rcubed like this.
  4. Roxbororob

    Roxbororob Supporting Member

    Jun 8, 2015
    Montreal
    I kept the cap across the rocker switch also (had forgotten this).
     
    FranF likes this.
  5. JacklegBass

    JacklegBass

    Jul 4, 2004
    That was my point and why I kept that cap installed to keep the power switch contacts from pitting. I only eliminated the death cap.
     
    FranF, Sorado71 and Roxbororob like this.
  6. LetItGrowTone

    LetItGrowTone

    Apr 2, 2019
    If I'm not mistaken the safest type of cap that goes across a power switch is a different type (designed to fail open, not shorted). It's something like X or Y for different applications. Better Google it.
     
    rcubed likes this.
  7. If that cap fails open or shorted makes little difference from a safety perspective. The ground cap is a different story.
     
  8. Sorry, from your post, I thought you removed that cap, too.
     
  9. JacklegBass

    JacklegBass

    Jul 4, 2004
    ^^^ This is correct. ^^^
     
  10. LetItGrowTone

    LetItGrowTone

    Apr 2, 2019
    Well, either someone explains it here or we all Google it, because it's important.
     
  11. Roxbororob

    Roxbororob Supporting Member

    Jun 8, 2015
    Montreal
    The rocker switch cap is not connected to chassis ground (like the ground fault "death cap". If it fails open power will not be fed into the ground (and to you). Worst case is the on/off switch will be bypassed and the amp will have to be unplugged to turn it off.
     
  12. JacklegBass

    JacklegBass

    Jul 4, 2004
    Precisely...
     
  13. Actually, if the ground switch cap was left in place after grounding the chassis with a 3 conductor power cord, and the cap went open, it wouldn't make one bit of difference, safety or operationally.

    If it shorted, the cap would either burn up, or pop the line outlet circuit breaker, depending which position the ground switch is in.
     
  14. Roxbororob

    Roxbororob Supporting Member

    Jun 8, 2015
    Montreal
    Not sure I would like to test the response time of the breaker (IMO). :chicken:
     
  15. MauiMike

    MauiMike

    Aug 8, 2014
    Byers,CO
    Back in the day my rig kicked. A few years ago I down-sized the cabinet because it was a pain to haul around, but I miss that 18" Ball Buster!

    IMG_0022_20.JPG
     
  16. You lost your spelling too.
     
  17. Hello! It took a while, but I found this thread and am hoping to get some help. I just picked up a mid 70's 140 and absolutely love it! Loud, light and I love the tone! I am looking to find the year of production. I can only narrow it down to the years 72-76. With a serial number of 8787 would anyone know how to date it? Thanks in advance!
     
    StereoPlayer likes this.
  18. My 370 head has the date stamped on the amp chassis inside. I don’t know if that’s how your head is dated though.
     
    Last edited: Apr 12, 2021
  19. Thank you for the reply! I took the chassis out yesterday to see if there was any markings on it, the boards or the pots and there wasn't a year marked anywhere. There are other numbers on the boards, but none that make sense as a year indicator.
     
    StereoPlayer likes this.
  20. JacklegBass

    JacklegBass

    Jul 4, 2004
    Your best chance for narrowing it down within a few months is to find the manufacturing date codes on the pots, large chassis-mounted capacitors, or the power transformer. For example, your pots may have a manufacturing code something like "137-7407" which would indicate they were made by CTS (137) in the 7th week of 1974.
     
    Sorado71 and Rocker47 like this.
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    May 8, 2021

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