1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
    TalkBass.com has been uniting the low end since 1998.  Join us! :)


Discussion in 'Amps and Cabs [BG]' started by Broncrider32, Oct 23, 2004.

  1. Broncrider32


    Feb 21, 2003
    I just bought a used SVT II Pro head on ebay...when i turned it on I had no sound. Only when i cranked the volume I got "sum" sound. I noticed the mute/pad LED is red even though i don't have it set to be muted. Is it the power tubes that need replaced? If you guys think that is the problem I have no idea on what type, brand, how many tubes to get. I need sum help asap I really need to get this amp up and running.

    Thanks, any advice is really appreciate
  2. Power tubes are 6550 set of matched tubes 6 off, you might be able to see them glow if still good, but dont mess with unless you are confident working with valves and electricity.
    Sovtek, electro harmonix or makes such as those.

    It could be the pre amp tubes, 5 off i think mainly 12ax7 and 1 off 12au7 if i recall ( 4 x 12ax7, 1 x 12au7 )

    You could try connecting the slave out to another amp to see if the pre amp side is working, this will tell you if the power amp tubes are dead ( more likely )

    Could be other faults but tubes most likely

    Be careful working with tubes and electricity as it can kill you !
  3. Don't assume the problem is the tubes just because it's a tube amp. SVT II Pro's have problems with their protection circuitry and they do exactly what you describe. Ampeg has a "fix" for the problem. Ampeg Insider could direct you to a service center who can do it for you. Before you go throwing money at tubes, remember, it's the AMP that's not working.

    Also, be VERY careful of the advice you take concerning the amp. Here's a PRIME example of good intentions but little knowledge being extremely dangerous:

    A tube's "glow" is no indicator of it's operation. All you're seeing is the heater filament which warms a tube's cathode to make it emit.

    ...or more importantly, leave it alone unless you KNOW what you're doing, and it's obvious that the original poster, or the "advisor" in this case, does not.

    This is the one bit of solid advice. You don't need to be a tech to use the slave output, but then this:

    ...has no bearing to the topic. Assuming power tubes are likely dead is just plain ridiculous. An amp will usually still "run" with some dead output tubes. My V9 had HALF its output tubes DEAD when I got it and the guy I bought it from had no idea ANYTHING had ever been wrong with it!

    90% of ALL problems with tube amps are NOT the tubes!!! That is a myth that is perpetuated by tube dealers to help sales and amp makers to excuse poor design/construction.

    Be equally careful handing out and taking amp tech advice. In some cases, even with the obvious disclaimers, you can be held legally responsible if someone follows your "advice" and hurts/kills themselves. In other words, leave the tech talk to the professionals
  4. notanaggie

    notanaggie Guest

    Sep 30, 2003
    Seems I heard it's just the early ones that had that problem. There was a posting some time ago that had that info.
  5. atoni


    Jan 23, 2004
    Helsinki, Finland
    Endorsing Artist: Salo Guitars
    The PEAK/MUTE lite is on whole time, right? So maybe there's some kind of shot-circuit in preamp section (or somewhere else)? Have you asked the seller about this problem? Maybe it's been got broken during delivery.

    Let some good technician take a look at it.

    Hopefully you'll get it working. It's a nice amp :)
  6. My intention wasnt to be un helpful but to pass on some possible tips, no im not a tube amp engineer but i am an electrical technician.

    The guy was asking for help if we get criticised for giving it we might as well not bother to offer any help however small !!

    In my experience of working with Valve amps the tubes are normally the likely items to fail and although a glow doesnt mean they are good it at least means they are alive in some form !

    The forum isnt here for show offs to make wise cracks at peoples attempts to help, all the negative tips have just pushed the guy down to the nearest shop for repair.

    We all try and help each other it may be limited in its facts but a little may just solve a simple problem.

    The guy was asking for possible help not the directions to the nearest Ampeg repair centre !

    And as said in my post if you are not qualified or competent dont mess with valves or electricity, you cant get clearer than that.
  7. There's a big difference between offering tips that anybody can follow and advocating amp self-repair. If your car doesn't work, you take it to a mechanic unless you are qualified to service it because there is a distinct possibility you could do more damage than good just messing around. The same appiles to amps with the further caveat that an amp's inside can KILL you.

    And statements like this lend creedence to the idea that you are somehow qulaified to offer repair advice. Look at the statement: "In my experience of working with Valve amps"

    Notice you didn't say 'playing' or 'using.' You said 'working' and that implies that you work on them. That's misleading.

    There were no wise cracks and I'm no show off. That amp NEEDS to go to the shop. Fixing it is not something that the typical end user should even contemplate attempting. It's not "negative" advice, it's correct advice.

    Amp malfunction is NOT a 'simple problem.'

    He got the answer he needs. He said he had already tried all the diagnostics he could think of and couldn't find the problem. That means it's time for a professional to take a look, not to just start swapping electronics parts on the off-chance that it MIGHT fix "something."

    You are not quailfied to give advice about amp repair and whatever disclaimers you recommend imply that you are somehow qualified to give them. There is a LARGE difference between electrical work and electronics work.
  8. Whatever !
  9. And you are ?? what makes your opinion so perfect, dont tell me you are an Amp engineer, i bet you dont do DIY either, get a life
  10. Since you so eloquently like to put your foot in you mouth, I won't add to it, but you should know....

    Umm.... yeah. Sorry to disappoint you.
  11. Excellent then i hope your advice will help the original starter of the forum.

    No offense was meant and like you was trying to be of assistance to fellow bass players.

    Maybe the guy with the problem can contact you directly to help sort out his faulty Ampeg ??

    Keep up the good work
  12. I USED to work at an SLM (Ampeg) service center, which is precisely why I referred him to Ampeg Insider. This was a common warranty issue and Ampeg is pretty good with customer service.
  13. Thanks, only wished the Ampeg service centres in the UK were not so pricey, plus we only get 1 years warranty while you guys get 5 years in the US .
  14. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    As someone posted, that protection problem is only on early versions of the SVT-2PRO. And, yes there is a simple fix.

    BUT, the peak/mute light has NOTHING to do with that protection.

    The POWER indicator shows a power amp fault, if one exists. From what you say, that isn't the problem.

    So if the peak/mute is on, AND the amp acts muted no matter what you do with the mute switch, probably there is a problem with the mute circuit in the preamp. Anything from a bad switch to a component failure in the mute circuit.

    Should be simple for a technician to handle. And much cheaper than output tubes.
  15. jusplayinmybass


    Apr 17, 2003
    Conyers, Ga
    Keith McMillan Instruments, SIT Strings, Accugroove Cabinets
    I used to own an SVT 2Pro and had a similar problem. the only difference is that the mute/peak light didn't light up until I cranked the input gain and played. I did get the muted and highly distorted output though. I found that if I plugged a 1/4" cable into the preamp out or power amp in and take it out, it would clear right up. I was told that his was die to pollution on the contasts. When i put it into a rack, I didn't have this problem. If this doesn't help, take it in. If it does help, you still might want to take it in to get checked out. B Easy