Ampeg troubles...

Discussion in 'Amps and Cabs [BG]' started by kZapner, Nov 7, 2005.

  1. kZapner


    Nov 7, 2005
    Hey guys, I've been having a problem with my SVT-200T head and SVT-410HLF cab. After anywhere from 15-30 minutes of play, the sound dies out (and sounds distorted while dying). It sounds like a dying pre-amp battery, but I assure you, that's definitely not what it is. If I slap the strings against the pickups with my palm, the amp will basically reboot and work for anywhere from 10 seconds to 2 minutes after that. The shop where I had my head worked on assures me that they can't find a thing wrong with it, and have run high-volume tests on it twice. I only put it in there for a pot replacement. I'm using a 1/4" monster speaker cable, which is brand new (Wouldn't have bought MONSTER, but for some reason it was the cheapest, go figure). I've tried different basses, different instrument cables, and still the same problem. I read on another thread about a fuse in the cab, I guess on the X-over. Could that be a problem? Or could insufficient power be a problem? Sorry to be wordy, but I wanted to give you as much info as possible. Thanks for any help...

  2. kZapner


    Nov 7, 2005
    Sorry, it's a SVT-410HLN, if that really even matters. It should be the same, but just in case...

  3. Erm, if your slapping the strings really hard and it starts working, it sounds like it could be your bass, or a cable, ie loosing a connection somewhere along the lines

    Have you tried using a different bass and cable? (would also explain why the shop found nothing wrong)
  4. theshadow2001


    Jun 17, 2004
    I agree if your bass has a pre amp it could be something to do with that. Sounds like when you hit the pick ups with the string your causing a short on the electronics somewhere. Try your bass on another amp if you can and see if the problem still arises when you do. Also it could explain why it sounds likea pre amp dying.....because that might just be what it is....
  5. kZapner


    Nov 7, 2005
    No it's not the bass, I play it on a Peavey Firebass 115 every Sunday at church. For youth band I brought my rig because I don't care for the sound of the Peavey. I ended up playing on it anyway because I couldn't get mine to function properly. I also tried a different bass and instrument cable with it and still had the same problem. The other bass did not have an active EQ if you're wondering. Oh, and also, I had the head running through the sound system through its XLR out, and the sound died in the system as well. Thanks for the input guys.
  6. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Short answer.... needs service.

    Longer answer.... If I had to bet.......... I'd bet that there is an open resistor to ground on the input of some stage probably in the preamp..... maybe a bad solder joint.

    Could be wrong, but I've seen it a couple times before on various things. Once was on a proto when a newbie engineer forgot that part.... he never had it on long enough to have it drift off...... but we found it when gig testing.

    If I am right, it will likely be on one of the stages with an opamp like a TLO72 on it, and a coupling capacitor feeding it.

    The amp can work fine for a while, because the bias takes a long time to drift off. The opamp input is held referenced to ground by the capacitor, but the voltage drifts slowly as the capacitor charges..... eventually, it is "off" enough to cause clipping and bad sound... and later would quit entirely.

    Hitting it with a big signal will probably discharge the capacitor through the overvoltage protection on the opamp, and give you some more time working again. Not much, as you have noticed.

    Try that on your shop folks, and I'll bet it gets fixed......... They just didn't know what to look for.
  7. kZapner


    Nov 7, 2005
    Alright, Thanks Jerrold, I'll talk to them about it.
  8. 8mmOD


    Mar 20, 2005
    I endorse & use Tech 21 pedals, Eminence loaded cabs, EMG pickups, Jim Dunlop picks & Ernie Ball Strings, BC Rich Basses.
    I'm With Jerrold on the cold solder joint diag, but I don't have the experience to narrow it down specifiaclly to an op amp. :) I'd personally have to open up the box, pull out the boards and look closely until I saw the failing joint. A few of my late 80's & early 90's Ampeg's have needed some solder joints touched up & it's a real easy fix. I hope you get it worked out.
  9. specplyrz

    specplyrz Banned

    Nov 11, 2005
    Could it be the seemingly, at times, lack of quality control at Ampeg that is the problem? Overheating rack mounted amps, new "special racks from Ampeg" with holes drilled in the sides for proper air circulation? Owners complaining of bad product "right out of the box:? :confused:
  10. specplyrz

    specplyrz Banned

    Nov 11, 2005
    Jerrold Tiers (formerly known as Ampeg Insider)

    Mr Tiers;

    Are the new series of rack mount amplifiers from Ampeg, (svt 6 pro)all going to have front to rear venting? Seems to make more sense than side venting for a rack mounted device? :rollno:
  11. Im going to chuck my opinion in here, just because :p

    I dont think ampeg will remove anything from the front of the rack mount units, so im guessing that they wont have front to rear cooling

    I will also say i dont think its that nessicary, my SVT II is side vented, and all tube, so a hell of alot hotter than the ones with SS power sections, and ive never had any problems in its little 4U case
  12. specplyrz

    specplyrz Banned

    Nov 11, 2005
    Thank you mohawk. It's just that alot of users had over heating problems with the side drawing of air....the new pro 6 if front to rear...thought maybe thet modified the design? :hyper:
  13. maybe it is then, just dont remember seeing any venting or such on the front off it :s