What can you touch in an amp while it's on?

Discussion in 'Gear & Equipment' started by narad, Mar 20, 2021.

  1. protest

    protest SS.org Regular

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    Do you think you'll actually be able to fix the problem if you have to ask what you can't touch?

    Not trying to be rude because trust me I have no idea what you can't touch either. Just saying that amps aren't guitars, so ask yourself that question before you poke around in something that can kill you.
     
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  2. Deadpool_25

    Deadpool_25 SS.org Regular

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    Where the fuck is the “love” button?

    (Awaits inevitable shenanigans)
     
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  3. Deadpool_25

    Deadpool_25 SS.org Regular

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    Wait. Wtf. You have a 5150 and you’re concerned with a rattling noise in some other amp? Dude, Japan is a pretty small island. Pick a shore and feed that amp to the fishys.
     
  4. Deadpool_25

    Deadpool_25 SS.org Regular

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    I call dibs on @budda ’s AxeFX 3. As far as I know the guy is healthy and not crazy enough to go poking around in powered on amps ( :) ) but I mean...just in case. /shrug
     
  5. narad

    narad Progressive metal and politics

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    Thanks, that's helpful to hear. It's amazing to me that after 20 years of buying/playing amps, I'm still learning new things like, hey, turn that amp up, and the OT can basically become a metal speaker. But what makes it tough now is just ...where does one draw the line between normal and unacceptable behavior? And the Jim Kelley amps were basically sold with attenuators, so I'm surprised to encounter this sort of problem when using one. But without having others to compare against, I don't know if this is an outlier OT, and maybe another would be better, or to suck it up (or sell the amp).

    As far as I'm aware, the amp is based on an old ampeg SB12. It's an amp fro 1980 though, so, a new transformer from the builder might be difficult. Though he had the reissues with Suhr only a few years ago, maybe it's not a big deal. But who's to say that one wouldn't also make the sound...

    It's not that they're rare and like therefore I can't find one. It's that they're rare, and therefore charge an arm and a leg. What do you think a reasonable amount to fix this problem would be? Based on my previous experience with techs in Japan, I have a guess at what they'd charge. I imagine it'd be around $1200-$1500 if it involved replacing the OT or treating it in some way. It'd cost about $300 to send the amp to a tech, take it out of the chassis, look at it, put it back in the chassis, and send it directly back to me, that much I'm sure.

    This kind of cost changes the perspective on everything. There's a Jim Kelley F.A.C.S. amp nearby for about $5k. And while that's a silly amount for an amp, I'd likely be $4.5k in after such a repair anyway, for an amp whose market value and condition isn't anywhere near the F.A.C.S. model. So to be clear, this thread isn't "I'm hoping to dive in and rebuild whatever part of this amp is giving me problems". It's, "is this vibration the cause of the transformer or tubes jostling around in an improper way, or do I spend half the price of the amp to repair it?"
     
  6. narad

    narad Progressive metal and politics

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    I think if there's a loose laminate, or transformer mount, or tube, or if there is something metallic but somewhat free-floating in the chassis, then I'm okay trying to fix those. If rattling could be caused by something like poor filtering in the power section, I wouldn't be trying, but the symptom is the same as if something metallic was just brushing up against something else. At this point I'm starting to rule that out...maybe something is rattling against the inside of the OT in some way... but ya, in theory I was definitely willing to consider something just not being bolted down 100%.

    Well I have a block letter, which are increasingly being referred to as the masterbuilt 5150s, assembled by hand in the USA. It's only natural that it doesn't rattle ;-)

    Actually my 5150 is noisy, but it doesn't suffer from any mechanical noise that I can tell. It's not a great master volume, but it's reasonable. The Jim Kelley on the other hand is non-master volume. The whole idea is to get the gain from the power section, and it's a very smooth distortion that's very musical and singy, but has a lot of clarity. Single line leads and Holdsworth stuff really suits it. And on the clean / light break up, it can do both fender and vox type things very nicely, and has an active EQ. It's an interesting amp, and I was skeptical before buying it, but now I'm seeing a bit of the appeal. So maybe some more time before it goes to the fishes.
     
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  7. Emperoff

    Emperoff Not using 5150s Contributor

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    Aham. And have you calculated how much your demise would cost? :lol:
     
  8. narad

    narad Progressive metal and politics

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    Sure, but what I'm saying is:

    what is the chance of death from touching the amp cabinet while it's on?

    what is the chance of death from touching the amp knobs while it's on?

    what is the chance of death from touching the amp tubes while it's on?

    what is the chance of death from touching the amp OT while it's on?

    I think we all approach #1 & #2 like it's virtually 0%. And repair guys on youtube seem to approach #3 and #4 like it's virtually 0% (and these are also the aspects that I would like to rule out as source for the high freq resonating). Is it? If not, why? To what other aspects of the amp does this extent? Knowledge is power, man.
     
  9. mikeymike

    mikeymike SS.org Regular

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    How loud was your amp cranked in your 2nd video? How much attenuation was going on? What kind of attenuator were you using? Were the impedances correctly matched to the amp (not the speaker, some dolt could have swapped speakers)?

    Why are repair costs so high over there? That's absurd man. An OT swap is not that hard, you just remove the primary from the power tube sockets (and the center tap from the b+) and secondary from the output jack. Unbolt the transformer and bolt in the new one and re-connect those aforementioned connections. I have no idea what your circuit looks like or what the topology is though. You could open it and take a look around safely as long as you don't touch anything. Be sure not to set the amp on the tubes. Big rolls of blue tape with the PT sitting in them (or rolls of sandpaper or duct tape or whatever) help stand the chassis up high enough to keep it off the tubes. Boss pedal boxes work too on the flat spots of the chassis bottom.

    Again though, how loud were you playing in your video? Was the amp dimed? Close? Need more info. You could try to get it repotted, there has to be someplace that makes transformers in Japan.

    EDIT: Just read your reply to that other guy, it's safe to touch all 4 of those things. Don't burn yourself though. Also check the OT for any bobbin connections (is it inside a bell housing or exposed?) Pics would be nice.
     
  10. stevexc

    stevexc SS.org Regular

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    Dunno what everyone's talking about. You can touch anything in the amp while it's on.


    ...once.
     
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  11. mikeymike

    mikeymike SS.org Regular

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    I was going to say this too lol
     
  12. narad

    narad Progressive metal and politics

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    Like watch this guy at 3:40. I had no idea that that wouldn't kill the guy outright. Is this just because it's maybe a lower watt radio that he feels comfortable doing this?



    I mean, I'm scared to just try to hold the OT to dampen vibrations, this guy's like poking around the inside of it.
     
  13. laxu

    laxu SS.org Regular

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    Basically you should be treating the amp like it's on if the capacitors haven't been discharged. Things on the outside are safe to touch, things on the inside are not. The channel you linked for the transformer video has another one that shows how to build a tool to discharge the caps safely. This video might be helpful too:



    First thing I would do is just disconnect the speaker and get the amp out of its cabinet after it's been turned off for a good while. Then you can know if it still rattles when decoupled from the cab. If it's the case, you know the noise is coming from the amp.

    Then it's a question of finding where. I'd start by tightening every screw you can find to make sure it's snug. Use a plastic handle screwdriver.

    Since your issue is audible when playing, maybe use a looper to play a chord that causes the problem so you can try to listen where the noise originates. If you can pinpoint it to a transformer, see if holding the bell covers dampens it or if adjusting the screws on the transformer bell covers will change its pitch.
     
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  14. diagrammatiks

    diagrammatiks SS.org Regular

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    Is it normal in that it happens, yes. It it normal in that it's good? no. It's very very stressful for your transformer to be running that hard. In my two notes if you run the amp at full through the load box, the inductive load will also start to hum and track the output frequency. That's not super good for the loadbox either.

    as to your other question it's not really an issue of what you can touch more so what safety precautions you should be taking for each component.

    that transformer with no end bells scares the shit out of me.

    in terms of the problem it seems that jim is pretty adamant that this isn't a problem. It could very well that due to the wire, winding pattern, laminations used, potting etc that the transformer just hums more then normal and he's ok with that due to the tone result.

    additional fun things i've done to myself while working amps.
     
  15. StevenC

    StevenC SS.org Regular

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    I just remembered you're in Japan.

    Have you tried goosing it with a Jan Ray?
     
  16. narad

    narad Progressive metal and politics

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    Soon.
     
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  17. AltecGreen

    AltecGreen SS.org Regular

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    How much electronics do you know? I don't even want to offer advice to anyone who does not know basic electronics. You do have to respect the voltages in a tube amp and let alone one that may have an issue.

    I had a friend who was building a tube amp kit (high end audio) and was having problems. He powered it up without wiring a ground back to the outlet and had no way to discharge the main power supply capacitors. There was no easy safe way to discharge the capacitors at that point. I had to button it up and told him to leave it alone for a long time.
     
  18. narad

    narad Progressive metal and politics

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    Lol, I don't know how to answer that. Basic knowledge?

    At any rate, amp is getting picked up today by the shop that sold it to me. They're going to have a look at it and set it up for the 6V6 tubes it's actually supposed to be running. I don't think that'll fix all the issues, but breakup at a lower volume would help indirectly.
     
  19. AltecGreen

    AltecGreen SS.org Regular

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    Let me know if you still have problems after getting the amp back. Hopefully the shop will make sure there are no basic safety issues. What tubes are in there now?
     
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  20. nightlight

    nightlight SS.org Regular

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    Glad the shop picked it up.

    If you are worried about poking about in an amp, you're not alone. Best not to mess with high voltage electrical equipment if you don't know what you're doing. Even regular audio prducts have a warning in the manual that parts are not user repairable and pose a risk of electrical shock.
     
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