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Thread: 2 Channel H combo question - tube(s) rattling?

  1. #1
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    2 Channel H combo question - tube(s) rattling?

    My 2011 H is making a strange noise. I'm not an expert so forgive me if I don't describe it correctly. If I tap on the top of the cabinet I hear rattling and it's also audible through the speaker. It's not the reverb. Could a tube be loose? I've also been hearing a pinging sound when say hitting an open chord. I say ping because it's a high pitch over tone. I don't think it's my guitar as I don't hear it through other sources.

    Thanks for any suggestions. If that's too vague I'll try to describe it more.

  2. #2
    Plank Spanker justmund's Avatar
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    One of the tubes could have gone microphonic?

    http://www.tubedepot.com/microphonics.html

    Have you got spares you can do some testing with?

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    Member RichardJ's Avatar
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    Definitely sounds like a tube on it's way out, is the sound distorting earlier than it used to? Have you tried, carefully and with the amp off and cooled down, to simply take the tubes out and re-seat them in their sockets? I had similar in my EL34 Koch amp and it turned out that one of the power tubes was on it's way out. Does PRS have diagnostic process they could go through with you?

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    Thanks for the suggestions guys. I've wonder about the microphonic tube scenario. Based on the video it doesn't seem to be the same issue, but I guess that could vary. I will pull the back off and check to see if any tubes are loose. I won't go much further than that. This amp, although a 2011, probably has less than 50 hours on it and has spent most of it's life here at home. I've had to replace the stand-by bulb and now possible tube issues sure disappoints me.

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    Happy Egads's Avatar
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    There was a thread on here a couple weeks ago about trouble shooting your amp. It had a video to walk you through the steps. It's good info and a good place to start.

  6. #6
    Quote Originally Posted by Ron View Post
    Thanks for the suggestions guys. I've wonder about the microphonic tube scenario. Based on the video it doesn't seem to be the same issue, but I guess that could vary. I will pull the back off and check to see if any tubes are loose. I won't go much further than that. This amp, although a 2011, probably has less than 50 hours on it and has spent most of it's life here at home. I've had to replace the stand-by bulb and now possible tube issues sure disappoints me.
    Sounds like a bone-simple preamp tube problem.

    PRS doesn't make tubes or bulbs, they buy them like everyone else, so any issues certainly aren't a result of a fault at PRS. Most amp issues are about the tubes. To complain here that you're disappointed because you have to change a tube on a 2 year old amp isn't a fair criticism.

    Tubes - especially modern tubes for a variety of reasons that include the fact that the machines used in manufacturing are growing very old - are a bit unpredictable. You never know when a tube will go microphonic or fail. You can test a tube one day, and it can measure fine, and then go bad the next time you fire up an amp. I've had brand new tubes go bad on lots of new amps by the best makers.

    And you mention that the amp has maybe 50 hours on it - not relevant when it comes to tubes, and some folks feel that the more the old style electronics sit unused, the greater the likelihood that firing them up will blow a tube.

    PRS uses European tubes, JJs and Winged Cs, on their US amps. One might have a different preference, but among modern tubes, these tubes have great reputations. They could buy cheaper Chinese tubes, but there would be more problems and they won't sound as good.

    When I was a kid in the 50s/60s, every drug store and hardware store had a large "tube tester" that stood on the floor about the size of a juke box. It was NOT an unusual sight. You'd bring in your suspect tubes and test them, and if you needed to replace one, you'd go over to the tube rack next to the machine, and pick up a replacement or two. I remember racks of RCA tubes at the drugstore I used to get sodas at as a kid, with the red and black boxes. If only I could go back in time to get some!

    I point this out because changing tubes was a ritual everyone did on their electronic equipment in the tube era. People didn't hire a technician to change a tube, it was done by everyone.

    Every tube amp manufacturer has disclaimers about tubes. Here's what Mesa has to say:

    "You may occasionally experience some form of tube noise or microphonics. Certainly no cause for alarm, this quirky behavior comes with the territory and the Tone. Much like changing a light bulb, you don't need a technician to cure these types of minor user serviceable annoyances and in fact, you'll be amazed at how easy it is to cure tube problems...by simply swapping out a pre-amp or power tube!" http://www.mesaboogie.com/US/Dealers/FAQs/faqs.html.

    The tubes that come in PRSes have a very good reputation among tube-o-philes, but they are still early 20th century technology, vacuum tubes.

    It's probably a microphonic preamp tube, all you have to do is lightly tap each preamp tube with a pencil to find the bad one. Pull it out (you may have to gently rock the tube in its socket to pull it). Plug in a new 12 AX7, you don't have to test the tube or rebias the amp at all with preamp tubes, and voila, you are done. So simple, I did it as a 12 year old on my first amp, nearly 50 years ago.

    Really, don't be afraid. If you can change a light bulb, you can change a tube. You don't even have to stand on a ladder to do it (though, hey, if you like standing on ladders, I suppose that's ok, too).
    Last edited by LSchefman; 09-02-2013 at 01:53 PM.
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    Thanks Lchefman, all good points! I remember the tube testers at convenience stores back in the day and fixing a hand me down TV myself. I had nothing to lose then. I guess the amp is a little more intimidating. I pulled the back off and tapped on the power tubes but haven't on the preamp tubes. I wasn't sure so I closed it up. After reading this I will dive back in, first I'll get a couple tubes to have on hand.

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    Member RichardJ's Avatar
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    +1 Les, I bought a complete set of new tubes directly from Koch, at some expence as there is nowhere near here I feel confident re-biasing it, because the amp was starting to sound a little 'off'. One of the new power tubes started to fail within a couple of months. Koch stepped up (as would most decent manufacturers) and ran me through the tests and sent out a new pre-matched EL34. It scared the crap out of me finding the bad tube but ultimately it all ended well.

    Even the best manufacturers rely on overseas made tubes and they do fail unexpectedly.

  9. #9
    Yup. Richard, and of course we rely on European (including Russian) and Chinese tubes for a simple reason:

    They aren't made here any more.

    Some people blame environmental laws (it's not illegal to make them here, by the way, just expensive and impractical), some blame the fact that when the original tube makers stopped making them, they sold the old machines off. The reason they're still made in the Eastern Bloc countries has to do with the fact that Russian military equipment remained tube powered in many areas (possibly due to the fact that semiconductors like transistors can more easily be wiped out by the electromagnetic pulse of a nuclear attack than tubes).

    The JJs are made in the Tesla factory in the Slovak Republic. And the Winged Cs are made in Russia. These are among the most highly regarded tubes currently in production.

    A lot of people feel that Chinese tubes are improving, though I'm still partial to the European and NOS tubes you can find.
    I saw ten thousand talkers whose tongues were all broken...

    Website: http://www.elfxi.com

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    OK, next novice question... The preamp tubes are inside silver sleeves that appear to be screwed to the amp chassis. I haven't taken the back off again yet, but just curious if these sleeves will have to be removed to get to the tubes. If these have to be unscrewed to get to the tubes will I need to remove the chassis to get to them? I'm not afraid to change the tubes just need to know the procedure.

    Thanks.

  11. #11
    The tube retainers are spring loaded, they simply come off with a half twist. There's a little spring between the top of the tube retainer and the tube itself. You can press down a little on the tube retainer to free it up while gently twisting a half turn. It simply comes off with very little effort, and you don't have to remove the chassis.
    I saw ten thousand talkers whose tongues were all broken...

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    Thanks, that was what I was hoping. Definitely a preamp tube. I can run my multi-effects pedal through the FX Return and no sound issues. But through the front of the amp I get the tube distortion or microphonic issue, it acts just as in the video above. The H has a variety of preamp tubes (12AT7, 12AX7, ECC83S, 12DW7) so I need to find out which one is the culprit to get the right match. And I've got a gig Saturday night...great timing on my part...

    Thanks again for the help!

  13. #13
    Quote Originally Posted by Ron View Post
    Thanks, that was what I was hoping. Definitely a preamp tube. I can run my multi-effects pedal through the FX Return and no sound issues. But through the front of the amp I get the tube distortion or microphonic issue, it acts just as in the video above. The H has a variety of preamp tubes (12AT7, 12AX7, ECC83S, 12DW7) so I need to find out which one is the culprit to get the right match. And I've got a gig Saturday night...great timing on my part...

    Thanks again for the help!
    ECC83s are simply the European name for 12AX7s. a 12DW7 is a phase inverter tube (usually) and is probably not the culprit. If you do the tap test with a pencil, you will find the offending tube without much screwing around.

    The JJ 12AX7/ECC83s are widely available, you should have no trouble finding a replacement. Same with the 12AT7.

    Incidentally, the V-1 tube is sometimes going to tap a little louder than the others even if there's nothing wrong. When you tap the microphonic tube, you'll know it. It'll ring, it'll be louder, and sound different from the others.
    Last edited by LSchefman; 09-07-2013 at 05:25 PM.
    I saw ten thousand talkers whose tongues were all broken...

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    Thanks, I've been looking at tubes on line and will place an order. Curious thing... Thursday night a tube was squealing. Friday I took the back off and tapped around and nothing. Had it on 2-3 hours and it worked fine. Put it back together, practiced with it Saturday and played a three hour gig Saturday night and it worked flawlessly. I'm still going to order a spare set of tubes.

  15. #15
    Senior Member 11top's Avatar
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    I had the same thing happen with my Custom this week. I replaced a weak ECC83, and so far, so good. I played a four hour gig last night and it sounded great.
    Sh*tter's full

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    OK, it's been a while since this thread. I've replaced my preamp tubes since and thought I had the problem solved. But now again when I tap on the top of the amp I get a tube rattle. I have removed the back and it seems the power tubes may be the culprits. I can tap on them with a pencil eraser and get that rattle. And it's audible with amp on. No hums or squeals but a definite rattle. Am I right in thinking these need to be replaced too? Are JJ's a good choice as well?

    Thanks again,
    Ron

  17. #17
    Senior Member jfb's Avatar
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    Quote Originally Posted by 11top View Post
    I had the same thing happen with my Custom this week. I replaced a weak ECC83, and so far, so good. I played a four hour gig last night and it sounded great.
    I need to play one of these. I think it might suit me for a rock amp.
    Plank Owner

  18. #18
    Quote Originally Posted by Ron View Post
    OK, it's been a while since this thread. I've replaced my preamp tubes since and thought I had the problem solved. But now again when I tap on the top of the amp I get a tube rattle. I have removed the back and it seems the power tubes may be the culprits. I can tap on them with a pencil eraser and get that rattle. And it's audible with amp on. No hums or squeals but a definite rattle. Am I right in thinking these need to be replaced too? Are JJ's a good choice as well?

    Thanks again,
    Ron
    Could be a power tube...2 years isn't bad tube life for a guitar amp power tube. Lots of players replace them every 6 months. And power tubes don't usually respond to a pencil tap.

    You can find tube reviews all over the web...but the only way to know what's going to work for you is to try a few sets out with your amp, and that gets expensive. I've found that unless you're going with NOS tubes, the best thing to do is replace them with what came in the amp. After all, that sound is what made you buy the amp in the first place.

    Funny this thread is up today, as I have a feeling that one of my preamp tubes is going microphonic.

    One last thing: I've been fooled by resonances in the room, like light bulbs ringing from a resonance, and even by vibrating heating/cooling ducts and grilles.
    I saw ten thousand talkers whose tongues were all broken...

    Website: http://www.elfxi.com

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