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Tube Amp Maintenance

Discussion in 'Amps and Cabs [BG]' started by Ralphdaddy, Feb 10, 2005.


  1. Ralphdaddy

    Ralphdaddy Supporting Member

    Nov 6, 2003
    Chicago, Illinois
    Ok, I did a search, read all the pertinent info but nothing really took care of this for me. I'm basically trying to create a little online manual for what can be done at home by anyone with some time and a few bucks, and what can't. For example, where can I buy contact cleaner and what is the best way to use it? Do I spray it into the tube sockets or do I spray the tube contacts or am I dead wrong? I'm retubing with a full complement of JJ's, as opposed to the motley assortment of pre and poweramp tubes GC had in the thing. The manager said one of the preamp tube sockets has to be replaced and the crackling will disappear, forgot to add it's been crackling and I knew that going in, but I'd like to try cleaning it up myself before I pay some yahoo who may or may not know dick about my amp start poking around in it for 80 bucks an hour. So what can any tube amp owner do to their amp as preventive maintenance to avoid labor charges? I own a Mesa/Boogie 400+ specifically, thanks everyone. Hopefully this thread could get big enough to be truly useful to a lot of us who don't know as much as we'd like to but love the tube tone.
     
  2. Rockbobmel

    Rockbobmel Supporting Member

    Check out www.partsexpress.com There is some gold stuff (I forget what it was called). Also, the Mesa used ceramic tube sockets that, most likely, are OK. I would suspect it to be something else. Try wiggling the tube in and out of the socket a few times. This will help the contact area.
     
  3. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Caig DeOxit is what you want. You can get it at Antique Electronics Supply (tubesandmore.com), or any one of a dozen other online supply places.

    Tube sockets might benefit from an occasional little spray with contact cleaner, but "retensioning" is a more important concept. That basically just means squeezing the pins so they make good contact.

    Crackling can be due to a lot things. It "might" be the tubes, or it might be the tube sockets, or it might even be plate resistors, or the power supply capacitors, or any number of other things. But you're right, you have to go through a "deductive" process to figure it out. "Troubleshooting". :)

    PM is a very good concept. Probably one of the most important things in that regard, is replacing the requisite electrolytic capacitors every now and then. Those can go bad pretty quickly, especially if your amp's sitting in the garage unused for a while. People get way out into left field about the value of keeping the original capacitors in old Fender amps and that kind of thing, but at the end of the day, it's a safety issue. I'd rather have good caps than vintage "junk" that doesn't do the job. :)

    We could talk about this for a long time. :D
     
  4. Not really same question as his, but talking about tubes and the 400+ does that amp have a tube power amp as well as pre amp or just a solid state power amp?
     
  5. Rockbobmel

    Rockbobmel Supporting Member

    WHAT?
     
  6. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    Its all tube.
     
  7. Ralphdaddy

    Ralphdaddy Supporting Member

    Nov 6, 2003
    Chicago, Illinois
    Nonsqtr, you've given me a good bit to think about with your response.... What of all that you wrote can any novice do? I'm no electronics wizard so I can basically do the basic stuff like clean contacts and such. Is it allright to remove the sockets from the amp and attempt to clean them that way and push the contacts closer together? And how much contact cleaner should I spray into the socket? Enough to soak it down or just a short spritz? Once it's in, do I have to poke anything inside there to kind of scrape some of the junk off? If so, what's the best tool. I see Caig sells different types of DeOxit applicators and even little brushes... are these a waste of money? I recall someone saying a Q-Tip with the cotton end removed was a good thing to slide into the socket and wiggle around, but I'm not sure if it's good idea or not. Thanks everybody!
     

  8. I wouldn't reccommend fooling around inside tube amps at all if you're a novice about electronics. There are potentially lethal amounts of energy stored in those high voltage capacitors even when the amp is off and unplugged. You at least need to make sure they're drained before you start fooling around inside or you might be in for a nasty jolt. I can tell you from experience that 400VDC hurts like hell at best.
     
  9. Ralphdaddy

    Ralphdaddy Supporting Member

    Nov 6, 2003
    Chicago, Illinois
    Hahaha, thanks for the tip Mark, I'll do my best not to get shocked :) How do I know if the caps are drained? I haven't even plugged it in since I got hom with it, I turned it on to make sure it still worked ok, then turned it off and unplugged it. How long do the capacitors hold a charge? I'm not a total idiot with electronics, I know enough not to kill myself luckily, just not enough to know EXACTLY what to do and how to do it. Thanks for the warning and remarks though, I'll certainly bear them in mind.
     
  10. Rockbobmel

    Rockbobmel Supporting Member

    I have heard that techs would sit on one hand when working inside some amps so if the got hit, it would not go through their heart. It sounds like you are flirting with the wrong stuff. I take this stuff seriously when they say "no user servicable parts inside chassis"!!! Poking around with a butter knife inside will get you dead!
     
  11. Ralphdaddy

    Ralphdaddy Supporting Member

    Nov 6, 2003
    Chicago, Illinois
    I'm not disagreeing nor am I not taking it seriously, believe me I have no intention of dieing to save a measley 100 bucks! I'm just looking for info brother. You can always make more money is my motto... but not if you're friggin dead. So I'll probably do little more than replace the tubes myself.
     
  12. Passinwind

    Passinwind I Know Nothing Supporting Member

    I'm basically trying to create a little online manual for what can be done at home by anyone with some time and a few bucks, and what can't.

    Someone's already done that, and very well. Go to Ampage on www.firebottle.com, and be prepared to spend a few weeks educating yourself! Here's the direct link to the basic FAQ on amp maintenance and so on: http://www.geofex.com/tubeampfaq/taffram.htm

    BTW, I've been told that Caig Pro Gold is the right product for high temperature contact conditioning. If tensioning doesn't correct the problem, I just replace the socket, personally.

    The safety issues are very real. I've welded screwdrivers to steel chassis with 600VDC, and taken a few nasty hits that could've been much worse, as in lethal. The Amp FAQ in the above link explains cap discharge right off, since it's so important.
     
  13. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    Okay, all this talk of serious amount of voltage inside an amplifier has got me thinking. Should I be wary of anything when changing the 12AX7's out of my M-Pulse 600? I've done it twice now (trying to find my favorite tube thus far :D ) and have not experienced any problems, but after reading this thread I'm a bit worried.

    Are there any extra precautions I should take? I don't mean to hijack the thread, but this seems relevant to the topic at hand.
     
  14. Passinwind

    Passinwind I Know Nothing Supporting Member

    Ermmm...leave the pina colada on the other side of the room? :cool:

    Swapping preamp tubes isn't usually a scary deal, as long as the amp is turned off. I generally use a pot holder to keep from burning myself, and that would provide some insulation value as well.
     
  15. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Definitely. The high voltages aren't a problem unless you're "in" the chassis. Draining and discharging caps is one of the first things you need to know. The voltages can definitely be very dangerous, but if you know what you're doing, and how to protect yourself, it's not a problem. The screwdriver method definitely is very risky, don't try it. :)

    The best way to discharge caps is with a low-value resistor, like a 10k or 22k or something like that. It'll only take two or three seconds. The essential tool for the amp tech, is a digital multimeter. Those can be had pretty cheap, maybe thirty bucks at your local electronics store. You can use the multimeter for "everything", like verifying if your caps are fully discharged.

    Really, from a safety standpoint, the caps are one of the central issues. There's other more obvious stuff, like making sure the line cord is unplugged while you're working on the amp. :D

    The multimeter is your best friend. The rule is, "always check" before you plunge into something. :)
     
  16. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    I don't want to sound like I'm being overly anal, but it was a banana daquiri thank you very much :p
     
  17. Yup. A meter is essential. I have drain resistors made up with wires soldered to the leads and alligator clips on the other ends. I use 10k,5k,1k,470,100,10 10W power resistors. Probably overkill but I had them on hand.... Use the higher impedance ones on the higher voltages unless you want really hot resistors :D.
     
  18. Passinwind

    Passinwind I Know Nothing Supporting Member

    Can you say "young, and dumb"? No more cracks at a Darwin Award for me, thanks! [​IMG]
     
  19. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Yeah, well, I've been there too. :D

    It's not something to be taken lightly though. Back in my radio days, a good friend of mine got killed trying to discharge some caps with a screwdriver. He apparently got thrown backwards across the room, and hit his head on the exact corner of an oak filing cabinet. We didn't find him for three days, and it wasn't a pretty picture when we did. I shudder at the very memory. And I've had more than my share of "shocking experiences". Sometimes that's what it takes to learn the lesson. I'm very grateful to be alive. :)

    A word to the wise: don't try this at home! :D