Bad Power Cable?

Discussion in 'Amps and Cabs [BG]' started by jd50, May 13, 2022.

  1. jd50


    Nov 16, 2017
    Stevensville MD
    It's been driving me crazy trying to figure out what's wrong with my rig, and I'm freaking out a bit because I have a 4 hour gig tonight. I have an ampeg pf-500 head and 2 115 cabs. Long story short, 2 different heads stopped powering (or at least making noise) my cab, plugging headphones into the amp head worked. Is it possible for a power cable to be faulty in a way that it doesn't provide enough power for the amp to power the cab, but still kinda work?

    Ok now long story long. 2 weeks ago in the middle of practice my rig cut out, amp still had power and the fault light was not on. I swapped out everything frantically in the middle of a song, instrument cable, speaker cable, even a different bass. There was an extra amp head there so I tried that and everything worked. I figured my head had gone bad so I bought a new one (PF-800 this time).

    I wanted to be sure so I used my old and presumably bad head at home the past 2 weeks trying to reproduce the problem and it's worked fine. Finally last night while trying out my new head it happened again. I was more methodical this time swapping everything out one by one, although the first thing I tried was plugging headphones into my head and that worked! I pulled another cab over and plugged into that, still didn't work. The only thing I hadn't swapped out was the power cable, but that involves restarting the head which also fixed the problem. So I THINK the power cable was the only component I didn't switch out meaning that's most likely the culprit, but I'd like a sanity check before the show tonight.
  2. Jefenator

    Jefenator Supporting Member

    Aug 22, 2008
    Sorry for your run of bad luck.
    I've never had an IEC cable be the culprit yet. But you never know.
    If it was the same power cable with all the incidents, that would certainly merit trying a different cable!
    I always travel with at least one backup. I look for a reasonably thick gauge (16AWG) and a snug fit into the amp. (I got a cheap cable on Amazon once that fit very loosely; it went straight to the garbage.)
    The one that came with your newer head ought to be suitable.
    I hate to say this, but a quick search on your newer head model turned up some unsettling results:
    Ampeg PF-800 800-watt Portaflex Bass Head Reviews | Sweetwater
    Ggaa and Lobster11 like this.
  3. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
  4. jd50


    Nov 16, 2017
    Stevensville MD
    Hmmm.... I saw the reported issues of early bad runs of the PF-500 but didn't see those poor reviews for the 800. That sucks, I love the tone of these PF heads. It's odd that the headphone out worked. I briefly tried a used PF800 from guitar center that it might have happened with for 10 or 15 seconds but it was hard to tell. I decided to stop gambling with used gear and bought new. It's one thing to save a few bucks on used gear when I'm playing at home, but I don't want to take a chance when gigging.

    There doesn't seem to be a pattern either, over the past week I've left it on for hours at a time and played off and on throughout the day to try to reproduce the issue and nothing. Then last night after like 20 minutes it happened.
  5. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    IME/IMO if the power cable was the culprit here the head would have no power and not be able to produce sound through the headphones. To me this sounds more like a bad speaker connector on the head if it is the head itself and not speaker cable/cable connector related.

    Since you said that you A) "...swapped out everything frantically in the middle of a song, instrument cable, speaker cable, even a different bass" and B) "...pulled another cab over and plugged into that, still didn't work...", but you did have power to the head and could listen through headphones, I am still thinking faulty speaker connector on the head. However, I would look closely at the connectors on your speaker cable(s) to be sure they are genuine Neutrik.

    I believe you will likely find the solution to your problem in the speaker connector and cable/cable connector area, not the power cable. At least this is where I would concentrate my attention first.
  6. jd50


    Nov 16, 2017
    Stevensville MD
    Yea, when I pulled over the other cabinet I used a different speaker cable too, still didn't work. The only thing that made it work was restarting it and then I swapped out the power cable. I guess it's possible I've gotten several faulty Ampeg heads, the more I research the PF heads the more likely it seems but damn...
  7. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    That really sounds like the speaker connector on the head itself may be faulty. I'm having a really hard time seeing how the power cable could provide "some power but not enough". Remember too that when you swap out any cable, all the other connected cables jiggle/move a little as intermittent speaker cable connection might suddenly work.

    I have also seen cases where non-Neutrik cables would work intermittently on some heads/cabs and work perfectly or not all on others. I had a GK supplied cable with NEO112 II that was exactly that way and it did not have genuine Neutrik connectors.
  8. What Al said. ^^^ and ^

    Did it happen with both cabs connected and not with just one?

    What is the Impedance of each cab? Making sure you are not running two 4 Ohm cabs or one 8 Ohm and one 4 Ohm all of them result in too low a load for your amp.

    Two 8 Ohm cabs is the most you can run with them heads.
    MaxSpinrun and Al Kraft like this.
  9. jd50


    Nov 16, 2017
    Stevensville MD

    I agree the power cable theory is odd but the only other thing I could think of. I did go buy new 14 AWG Boss speaker cables after the first time it happened but haven't used them yet, I've been using 16G Live Wire speaker cables.

    I also have a speakon to 1/4 cable, I wish I would have thought to try that last night when it wasn't working before power cycling the amp head.
  10. jd50


    Nov 16, 2017
    Stevensville MD
    I have 2 Ampeg 115HE cabs, which are 8ohm. It initially happened with 2 of them daisy chained, I unplugged one and still didn't work. Last night it happened with just one. The other cab that I plugged into it last night was another 8ohm cab, GK Neo 112, still didn't work. I swapped out every single component before power cycling (and switching power cables). Power cycling fixed it right away, but I'm not trying to power cycle my head in the middle of a song tonight lol.
    S-Bigbottom likes this.
    It will short to ground on the way in and kill your head.
  12. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    The 16 gauge Live Wire cable should have been fine. IMO Live Wire makes excellent cables and uses genuine Neutrik connectors in most cases. As an engineer (albeit not an EE) I think the power cable either provides power or it doesn't in an application like this - I can't see it causing the symptoms/conditions you're experiencing.

    You could also have two bad heads...if you can have a technician do a quick check under warranty that would be a reasonable and logical next step.
    Last edited: May 13, 2022
    byacey and S-Bigbottom like this.
  13. kickysam49


    Feb 28, 2022
    I mean, it would be really nice if it was possible to blame the power cable, but an IEC cable is either going to supply power to the amp, not supply power to the amp, or toggle between the two if it is half plugged in. There's not really a whole lot of middle ground (pun not intended).

    One component you haven't mentioned testing is the actual source(s) of electricity. How many different locations has the rig failed in? You may want to get an outlet tester.
    Last edited: May 13, 2022
  14. Jaco who?

    Jaco who?

    May 20, 2008
    Does this only happen where your band practices, and not at home? If so, you might want to plug a voltage tester in at your practice space and see what it reads. kickysam49 - I read your mind:)
    kickysam49 likes this.
  15. jd50


    Nov 16, 2017
    Stevensville MD
    Good thought but it's happened at 2 different locations now, home and practice space. I guess to be safe I'll use my guitar player's markbass head (he plays bass in another band) tonight... ugh.
  16. jd50


    Nov 16, 2017
    Stevensville MD
    I've always been careful with that but was desperate to troubleshoot.
  17. sawzalot

    sawzalot Supporting Member

    Oct 18, 2007
    So if I read your post correctly, you've swapped out the bass, instrument cable, speaker cable, cabinet, and bass head and you are still having the problem. Both heads work through the headphone output. Yet you still get intermittent failures.

    Sherlock Holmes would say that once you've eliminated the impossible, whatever remains, no matter how improbable, must be the answer. If the power cable were bad, you'd lose the headphone output--I'd put the "bad power cable" idea in the "impossible" category unless there's something about these heads where the headphone jack will continue making sound without electricity. But, there's the continuum of the improbable to consider. I think it's highly improbable that you would get the same symptoms with all of those components switched out. So, it's either some other component that we're not thinking of, or something in the overall setup.

    My thinking immediately goes to the combined impedance of the cabs being lower than what the heads can produce. Certainly the symptoms match this scenario. Do the amps cut out as you raise the volume? Have you measured the nominal impedance of each cab with a multimeter? Each cab should read something near 8 ohms, if they are supposed to be 8 ohm cabs. Both wired together should read something near 4 ohms. I'd be interested in the output of that test.
    Al Kraft likes this.
  18. jd50


    Nov 16, 2017
    Stevensville MD
    That's a good thought but it happened with - 2 8ohm Ampeg 115HE cabs, 1 8ohm Ampeg 115HE cab, and 1 8ohm GK Neo 112 cab. And it just cut out in the middle of playing, turning the volume and gain knobs didn't change anything or make any sort of noise. I agree re: bad power cable, I think you guys have helped me rule that out.
  19. jd50


    Nov 16, 2017
    Stevensville MD
    Damn, reading over this thread Ampeg pf-800 update: shut down! and it doesn't seem so unreasonable that I have multiple faulty Ampeg heads... uh... any suggestions for something that gets a similar tone. I really love the Ampeg sound but now I'm more worried about my gear cutting out than I am my playing.
    Jefenator and Lobster11 like this.
  20. JeezyMcNuggles

    JeezyMcNuggles Suspended Supporting Member

    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    Mute switch
    SoCal80s likes this.
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