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Ampeg PF500 Issue (not a failure issue)

Discussion in 'Amps and Cabs [BG]' started by SuperK, Oct 24, 2013.


  1. SuperK

    SuperK

    Sep 12, 2012
    San Jose, CA
    I have a non-critical issue with my PF500. On the rear panel, there are three buttons related to the XLR out (Ground Lift, 0/-40dB, and pre/post EQ). Recently, these buttons have become recessed into the head. Before, when they were in the "out" position they would stick out 1/4" from the panel and when they were in the "in" position they would stick out 1/8" from the panel.

    Now when they are in the "out" position they are flush with the panel and when they are "in" they are actually recessed about 1/8" into the panel. I took the cover off and look at the circuit board that the buttons are attached to and it hasn't moved. All of the 1/4" ins/outs are attached to the same board so it's not moving easily. They still function perfectly. They're just a pain to operate.

    Any ideas? I attached two pics. First is buttons out, second is buttons in.

    Thanks.
     

    Attached Files:

  2. Remus_Redbone

    Remus_Redbone

    Dec 27, 2010
    Western AR
    Tough call remotely. You've seen it and know if the switches are mounted directly to the board or if they are attached to the board with stiff wire that may have bent and allowed the switches to "sink". Could also be the switches themselves and the buttons sliding deeper into the switch body where they slip onto the button that is part of the switch.

    Don't let anyone tell you it's your fault for not operating the buttons properly....
     
  3. jeff7bass

    jeff7bass

    Apr 9, 2009
    There's probably some kind of brace that gave way a bit. I'm just guessing though. Maybe open it up and look. Might be fixed with a little crazy glue.
     
  4. SuperK

    SuperK

    Sep 12, 2012
    San Jose, CA
    I'm pretty sure it's something like this. The PCB and switches haven't moved but the button covers must have slid deeper onto the switches. Looks like I'll have to dig a little deeper. I was hoping someone had seen this before and had an easy fix.

    Other than that the amp works great.
     
  5. 96tbird

    96tbird PLEASE STAND BY

    A true mystery! It's weird how they all are affected the same amount and at the same time if it is the button covers! any way. If nobody has any ideas, I guess you could actuate them with a cable end or a pen or pencil; any pointy pokey thing at hand.
     
  6. christw

    christw Get low!

    May 11, 2008
    Dayton OH
    I want to be Tesla (tinkerer at Dayton Amp Co)
    I haven't poked around in a PF500 for about two years but IIRC, it should be quite easy to determine the problem if you open it up. It's really not that scary. Just don't mess with anything and get a pic of what's wrong. I'm with the others, I think it's a loose brace or mini switchboard board.
     
  7. SuperK

    SuperK

    Sep 12, 2012
    San Jose, CA
    With no gigs this weekend, it looks like I have a little project tomorrow!

    I'll open it up and get into it in more detail. If I find the issue I'll take some pics and post them for posterity.

    Thanks for the help.
     
  8. SuperK

    SuperK

    Sep 12, 2012
    San Jose, CA
    Just a follow up....

    I opened the head up and removed the board with the buttons on it. Fairly easy to remove. The button switch "stems" are little white plastic things that feel pretty cheap. It feels like there are two positions that the outer button cap snaps to. The first snap is correct but if you push it hard enough it will move down to the second position. Bad design IMHO. As a quick fix I just pulled the buttons out to their original position and put a drop or two of crazy glue into the underside of the button where it snaps onto the switch. Then I turned the board upside down and let gravity do its thing. Gave it a few hours to dry and it's as good as new.
     

    Attached Files:

  9. 96tbird

    96tbird PLEASE STAND BY

    Cool. Bad design? It's an off the shelf part from a large maker; it is what is available at the engineered price point. I can see the electronic design engineers at Ampeg gingerly pushing those buttons in and out during testing. They don't get that the end user may be like a bull in a china shop.
     
  10. SuperK

    SuperK

    Sep 12, 2012
    San Jose, CA
    I only say it's a bad design because the 4 buttons on the front panel (Ultra Hi/Lo, etc) incorporate a much more heavy duty switch. I just don't know why they couldn't use the same switch on the 3 rear buttons. I understand about cost reduction, but 3 button switches?? What did they save, like $0.50???
     
  11. They didn't expect may people to use that feature maybe? I agree they should have given it more attention, these are sold to be used. "bull in a china shop" was unnecessarily harsh IHO.
     
  12. Remus_Redbone

    Remus_Redbone

    Dec 27, 2010
    Western AR
    As I said;

    Don't let anyone tell you it's your fault for not operating the buttons properly....
     
  13. My PF500 has one button on the back like that and since I never use it, I haven't worried about it. Good to know how to fix it though!
     
  14. 96tbird

    96tbird PLEASE STAND BY

    I didn't mean him specifically. I meant real world use by men, like we bass players.
     
  15. Kudos to you for fixing and posting the fix !
    These updates really help people out in my experience.
     
  16. What about our female bassists? :)
     
  17. jeff7bass

    jeff7bass

    Apr 9, 2009
    Give me my props for saying Crazy Glue might fix it!!

    :D
     
  18. 96tbird

    96tbird PLEASE STAND BY

    I shall posit that the vast majority of females are more gentle with stuff than guys. I mean my wife has sneakers that are thirty years old! ImageUploadedByTalkBass1383104270.315561.
     
  19. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Congrats on finding a solution to fix the switch.

    I wonder if some silicone glue could have been used to lock the button to the shaft. It would be reversible that way.
     
  20. Looking at that photo those switch stems look like they are made of that nylon-stype stuff that CA glue (like Crazy Glue) doesn't work very well with. Can't really tell.

    Still, the drop of dried glue might provide enough hold to prevent it from happening again.
     

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