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Shorted cables, fried coils, burned amps, shoddy power.....bring your backups folks.

Discussion in 'Amps and Cabs [BG]' started by will33, Jul 22, 2012.

  1. will33


    May 22, 2006
    Just got back from our regular gig we do about once a month. In the end, it all went well, sounded good, made decent money, etc., but it didn't start that way.

    Went through a couple amp changes, configuration changes, and some head scratching trying to figure out what the hell was going on. Started with amp shutdowns a couple minutes after power up, followed by working amps with too much "transistor radio" sound in them, followed by a couple trouble free sets, followed by a total failure in the middle of the last set followed by finishing out the night with my T-max, a single 12, and the best sound I had all night.

    I suspect some of this may've been due to a crap/shorted cable or 2, a shoddy powerstrip/extension cord/GFCI outlet or who knows what else. I basically overheated my 800rb and when my drummer jumped up to help pull cables/switch gear, etc. while the singer and guitar player did a number to buy us a couple minutes, he says "we got hot cables, man:)". Meaning speaker cables. First the rig died, then about 30 seconds or so later (maybe a verse of a song), the DI died.

    So, we throw the Tmax up there, don't get sound from the second cab. DI works good, good sound from one cab. So, we finish the night and all is well. Gig went great, we sounded really good, made decent money, got booked again, and possibly scored a nice paying private party gig out of it (have to follow up on that), plus, some older lady (older meaning 50-ish?) threw us $100 in the tip jar. In the end, it all worked out, and frankly, the Peavey amp with the known-to-be-good-cable, through the one good speaker that worked sounded great, best tone all night. I guess it helped getting rid of the bugs.:)

    Anyway, my point is, bring your backups with you folks. I've been dragging this 50lb. amp around with me to every gig I've played. Sometimes I play it and make the GK the backup because I like the Peavey. One time I used it to power monitors because somebody's poweramp crapped out. Most of the time it's dead weight. Tonight, it saved the whole show and it was one of the best shows we've had in a long time.

    If it weren't for "old faithful", it could've been one of the worst, and had a couple missed opportunities that may prove to be lucrative.

    I've been paring down my PA system/bass gear to make stuff easier to haul/set up, etc. but I've always found room for that old T-max. Tonight, it was worth it's weight in gold.

    Always have a backup plan folks, be it a spare amp, a DI, 2 speakers when you can get away with 1, etc. Hell, I chain together two 6 channel mixers instead of having a single 12 channel. If one goes down, I can still get vocals, acoustic guitar and kick drum. Crank the backline and bash the rest of the drums. Fun-loving audiences still have a good time. Beats the hell out of saying "fun's over folks, our stuff is broke".

    Now, to unload the stuff and see just what is fried in what and what is just simple stuff.
  2. will33


    May 22, 2006
    I'll take stuff apart, figure out the failures later. I've already loaded, unloaded, set up, tore down and loaded gear today....that's enough.

    It's 3,am....the fear is gone....I'm sittin' here waitin'....the gun's still warm....:).

    Yeah, I know it's supposed to be 2 am.....but it's 3.
  3. spaz21387


    Feb 25, 2008
    Portland oregon
    its always smart to have backups... I always have a tech 21 sansamp for this exact reason.
  4. will33


    May 22, 2006
    I've done this gig several times just cranking my rig and it carries the house fine....sounds good. Tonight, for some reason, it was sounding weak from the get go, ran a post-eq DI to the PA for some help. Turns out between that, and the spare amp, the gig was saved.....and turned out to be a really good one.

    Yeah, I'm an advocate for backup plans....:). You shouldn't show up with only one way of making things work, and if that doesn't work, standing there looking stupid.:smug: Improvise, adapt and overcome.
  5. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    After years of not having any amp failures, I've had two tubes go out on me and my bass go wonky on me as well in the last 3 months. I was able to fix the bass each time no problem, but the amps required home service. Fortunately I had my PF350 with me.

    So yeah, I'm rethinking this whole "no backups" policy of mine.
  6. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    I've never had an amp or a PA failure on a gig. I have also never went to a gig without a spare amp, spare cables, spare bass,etc..

    Nice save Willie.
  7. derrico1

    derrico1 Supporting Member

    Apr 12, 2005
    Charlottesville, VA
    Truth. Play enough gigs, and chances are you'll eventually suffer gremlins during the gig even if your gear is well built and well cared for.

    It's definitely well worth carrying at least spare cables and either a backup DI or micro head (for gigs w/ FOH support).
  8. jnewmark

    jnewmark Just wanna play the groove. Supporting Member

    Aug 31, 2006
    Stax 1966
    Third St. Cigar Records staff musician.
    I bring a whole travel bag filled with spare everything: cables, batteries, small tool set, straps, tuners, DI, AC cables, strings, and even a K&K pocket preamp. I went back to a lightweight rack setup with my Carvin BX1500, and my GB Shuttle 9.0 racked together. Paranoid ? You bet'cha ! I have had amps, preamps, cables, tuners, go down on the gig before !
  9. ToneMonkey


    Sep 27, 2003
    Newberg, OR
    WOW. Never in 46 years have I had a speaker cable short out on me, or for that matter fail in any way. Instrument cables yes, speaker cables no. Hope your GK is alright.
  10. will33


    May 22, 2006
    I suspect a shorted speaker cable started the chain of events, although, at the start the amp would shutdown after a couple minutes of being powered on. I thought that had been sorted out as a bad extension cord or powerstrip but I really don't know.

    Just hurriedly hooked up stuff that worked to get through the gig. It ended up going Peavey-1st set. GK-2nd and 3rd set and first half of 4th set, then the meltdown. Peavey and 1 speaker finished the night.

    Sort through everything as I unload the car here in a bit, but first, bacon and eggs.....mmmm.:)
  11. Kitsapbass

    Kitsapbass What key is this?

    May 26, 2005
    Bremerton, WA
    Sounds like it's going around. Earlier this year my Trace Elliot preamp went wonky...and last night my Yamaha PB1 did the same. At this point, I'm beginning to think it's new rig time when my tax return shows up...
  12. Sounds like a shorted speaker cable or cab. The 800RB lasted that long? Tough bugger, it gave plenty of warning there was a problem! Hot cable makes me think the cab. Confidence not high the 800RB survived (no protect circuit in the 800RB). Don't hook up a cab to the 800RB, instead check for DC voltage at the output jacks. should be will under 1VDC.
  13. will33


    May 22, 2006
    Well, so far, got a blown mains power fuse in the GK, and a woofer that isn't responding to the battery test. It is making some funny little noise but the cone isn't visibly moving like it should with a 9 volt. So letting the screwgun charge up while I go pick up fuses, run some other errands.

    Thanks for chiming in B-string. May have a question or 2 for you depending on how things go as I get deeper into this.
  14. I'll be around later today, about 5 pm Az (PST) time. ;)
  15. Jools4001

    Jools4001 Supporting Member

    I think last night must have been one for the gremlins. We played a new venue last night in what can only be described as a tunnel. The main bar had a sort of long alcove running off it where the pool table normally lives and that's where we were expected to set up...oh, and leave room for a corridor along the side of this space so that the smokers could get our into the garden...

    The only way we could jam ourselves in was for me to wedge myself beside the drum kit, the two guitarists in front of us so that we were BEHIND their cabs and the vocalist in front of the two guitars.We usually run everything except bass and drums through the PA just to give a bit more control and definition, except that last night we didn't run anything except vocals through the PA simply because it was such a nightmare place to set up in.

    The vocalists brother is a keyboard player in a very good functions band and he was out front telling us we needed more bass in the mix, so I turned it up. All you could hear in our tunnel was bass, the sound of our whole first set was like one of those 'bass only' youtube vids with just a vague awareness that drums and guitars are playing...although bizzarely, and against all logic, the vocals in the monitors were as loud as you'd ever want.

    Long story short, a Crown 1000XLS pushing 700 watts in an 8 Ohm Barefaced Big One cab is usually enough to cope with anything...but it cant project bass out of a tunnel and into a larger space. I ended the gig on our final song with my cab sounding very farty and looked around to see the Crown hitting the limiters hard...I hope the fartiness was just the amp running out of steam and that my lovely Barefaced cab has survived....haven't had the heart to test it today, I think I'll go into denial for a bit.
  16. Johnny Crab

    Johnny Crab ACME,QSC,Fame/Hondo/Greco/HELIX user & BOSE Abuser Gold Supporting Member

    Feb 11, 2004
    South Texas
    3 weeks ago, the keyboard/guitarist and I lost "wall warts" in our stuff due to low voltage at a venue(100 Volts RMS when checked after the fact). That made my BASSPODXTLive dead. Plugged direct into the BOSE on one of the "P bass" setups. Got thru the night but not with my sounds. Now I carry a spare supply and ordered some Red LED voltmeters to keep plugged into our power strips(we usually run 2 x 20A circuits, one to each side of the stage).

    Last week, my main Kahler-equipped bass had a string let go(Kahlers do that to bass strings eventually). Finished the song and grabbed the backup bass hanging on the BOSE to finish the night.

    Backups and/or having a "Plan B" prevents complete FAIL at a gig.
  17. will33


    May 22, 2006
    So.......couple things confirmed....

    Going out the hindend of the amp, shown here....


    I couldn't find any obvious signs of heat damage, burned wire insulation, etc., even though the speaker cable was hot. The speaker cable itself looks and tests good, although, there is sign of the wire insulation getting hot right up against the solder connection inside the barrel of the plug of the end that was plugged in the amp.

    The "8ohm" woofer it leads to showed 1.4 ohms and failed a battery test. Obviously a toasted voice coil.

    I pulled up the power supply board, didn't see any obcvious signs of heat damage/bulging caps on it. Shown here.


    I didn't take out the poweramp board yet, but checked all those ceramic resistors on it and they all checked good, at least while they're sitting there cold with no juice flowing. That doesn't really mean they're good with the juice flowing and the temp. up to where it would be during operation, but, read the correct resistance when cold and show no obvious signs of overheating.

    Shown here.....


    The real problem is on the other end of the amp. It's blowing fuses immediately when hitting the power switch, which means the hot and neutral are shorted somewhere. The switch is good and the fuse holder itself is good. Next stop is the transformer.:eek:

    I got about .6 ohms resistance across the hot and neutral where they go into the front of the transformer but I don't think that reading means much. There is a little diode laying across the hot and neutral in front of the transformer shown here....


    Hard to get a clear pic that close.

    Possible dumb question(s). I haven't run into this before.

    Can I get an accurate good/bad reading of that diode with a cheap little multimeter?

    It's on the A/C side of things. Would I need to pull it out and hook it up to mains power out of the wall to see if it does what it's supposed to be doing?

    Would I need to run something on the other side of it to draw current to be able to tell?

    Does viewing it as a check valve like in plumbing even make sense with A/C?

    Just replace it and see what happens, it's probably like $1?


    The mains power fuse blows as soon as juice flows. I can't check DC offset or anything else really until I can get the amp to stay on and I fear I may've cooked some transformer windings together. Something is shorting hot to neutral before it even gets to the rest of the amp and the tranny is about all that's left before that point.


  18. That component looks like a thermal fuse? Not sure I don't see it on the schematics. You may need to lift one lead from the bridge rectifiers one bridge at a time. Only one wire from the trans needs to be lifted. Anything shorted on the secondary will blow the fuse. With all secondary taps disconnected if the fuse blows then the transformer may be damaged. If lifting one section at a bridge rectifier doesn't blow the fuse then that supply is being shorted out. Bridge rectifiers can short but you may have shorted output devices.
  19. will33


    May 22, 2006
    Cool, thanks.

    I assumed diode just because the part # on it starts with a D and I don't recognize it as being a part I recognize.:bag:

    Looking now, some label is worn off, may not be a D.

    Looks like letters TCO, then something 138, the maybe letters PAB?

    I need a !#@&$%* magnifying glass for this stuff. :)

    It looks like a tiny black and yellow bullet and lays across the 2 wires going into the trans. One being the hot from the fuse, the other the neutral from the power cord socket. Although, when I pushed it to the side a little just now to get a better look, it's connection to the hot wire just snapped right off.

    I'll figure out what this thing is. It obviously needs to be fixed now and do whatever it does. It lays inside the first wrap of that insulation (basically big black electrical tape) that wraps the transformer.

    So if I disconnect all the secondaries and the fuse still blows, the transformer's bad. And if I disconnect one bridge rectifier at a time, and the fuse goes, bad output device? Or did I understand that wrong?

    I need to dig up the schematic and do this the right way.
  20. will33


    May 22, 2006
    Geez ^^ I need to do this stuff with a clear head.:p

    12 hour day + dinner+ couple beers = me tired.

    Here is the little part in question. Could move it out for a better pic now that the one lead snapped off.




    That things connects the 2 wires going in the front side of the transformer, one hot from the fuse holder, the other neutral from the power socket, so I figure it's a possible cause of the shorting. If I can figure out what that is and how to test it, or just replace it, I can then move on deeper into the amp.

    I have a schematic but no parts list, but, I don't see that thing on there. Granted I'm not the best with schematics. Takes a while to figure out what everything is, trace it in the amp and translate the diagram to the actual amp.

    Anyway, thanks for the help. If I can pin down what that thing is/what it's doing, I can take a couple more steps forward. The labeling is worn off one side. Picking up a magnifying glass today.

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