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Guitar Related Electronics - Where to Start

  1. Apr 20, 2012 #1
    My guitar amp's been acting up for the last year or so, and as I'm finishing up the second year of my electrical engineering degree, it's been occurring to me that my inability to do anything to even try to fix it is pretty sad. I'm pretty sure that something like this isn't outside of the range of my abilities, I just have no idea where to start. So my question is, where do I start if I want to be able to understand how guitar electronics (amps, pedals, pickups, etc.) work, to the point where I can do simple repairs and maybe even try my hand at designing effects boxes? I'm hoping there's at least a few people here who tinker around with their guitar equipment who can help me out.

    Thanks.
     
  2. jcsd
  3. Apr 20, 2012 #2

    turbo

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    What kind of guitar amp? If you can locate and buy an old Fender Champ or some other simple tube-based amp, you'll have a perfect test-bed for your tinkering. The amps are simple and the components are large enough to allow you to solder and de-solder them at will. Once you get up into the solid-state models, I can't help you, except for the in-guitar electronics.
     
  4. Apr 20, 2012 #3
    Well, I was a musician for a long time, I just happen to be designing music electronics in the last half a year and I designed two guitar tube amp before. So give it to us!!!!:rofl:

    Name your problem, provide the schematic ( if you don't have it, go on the web, there are a lot of schematics there. If it is a more common amp, chances is I have it).
     
  5. Apr 20, 2012 #4
    @turbo: It's a tube amp: Traynor YCV-50, though I don't know if it's simple or not. Even still, I've done very little with electronics outside of school as of yet, so I don't really know what I'd do with a simple tube amp if I had one. I guess that's my main issue here.
     
  6. Apr 20, 2012 #5
    I do appreciate the offer, but I'm more looking for advice about how I could get started learning about this type of thing so that I can do it myself. (Though maybe getting help fixing this problem is as good a place as any?)

    If you don't mind me asking, how did you get into designing music electronics?
     
  7. Apr 20, 2012 #6
    The main issue is school don't teach tube amp. I don't have Traynor schematics, Traynor is quite a common amp. You should be able to get the schematics. As I said, get the schematic, name the problem and we go from there.
     
  8. Apr 20, 2012 #7

    turbo

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    OK. That seems to be a decent amp by a decent company. The first thing that you ought to do is get some basic documentation (schematic and wiring diagram) so that you can start chasing down the problem(s). Hopefully, Traynor has not gone to all printed-circuit boards, so you can swap components easily. Good luck and come back for more if I can help.
     
  9. Apr 20, 2012 #8
    I designed my first tube amp in 1978!!!! Info was still around at the time!!! Go on line or someone might have a pdf copy of the old RCA Receiving Tube Manual. There are a lot of theory and description that you can learn.

    Tube is really similar to N-JFET in a lot of ways. Grid is like the gate, cathode is source and plate is drain. Grid is usually lower voltage than the cathode like gate is usually lower voltage than the source in normal biasing.

    For pentodes, there are two more input that is set at certain voltage. For your purpose, ignor them at the moment. You'll go quite far just imagine tube as N-JFET and read the schematic. You better know the rest of the components!!!!:tongue2:

    Now now, don't people jump on me about tube vs JFET, this is the real basic way of looking at it for the purpose of the OP.
     
  10. Apr 20, 2012 #9

    jim hardy

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    by all means get several tube manuals in your library.

    http://www.ebay.com/sch/items/rca tube manual?_dmd=1&_sop=12

    You learn 10X more by hands-on than from just studying. When i was in college(and slide-rules dominated the earth) the professors were bemoaning the loss of hands-on lab classes from undergraduate curriculum.

    i started college in 1964 and still prefer tube manuals from that era . Of course they're what i learned from in high school. The 1964 edition has a delightful 15watt hi-fi amplifier schematic . I built one from old TV parts and used it for decades. Hammond still makes transformers for DIY tube audio hobby market (Bless their hearts). Guitar guys like tubes....

    This digital clock from Ramsey should be an attention-getter in any modern EE department :

    http://www.ramseyelectronics.com/images/hk/NIXIE-w.gif [Broken]

    http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=NIXIE [Broken]
     
    Last edited by a moderator: May 5, 2017
  11. Apr 20, 2012 #10
    I forgot to mention, there are books out that specifically for tube amp. I have the "Designing Power Supplies for Tube Amp. by Merlin Blencowe. And I saw other guitar tube amp books. Go on Amazon and look for some of those.

    But if you just want to trouble shoot the amp, you don't need to get so deep into this. Of cause if you want to get into tube amp, it's a different story. But I doubted there is a job market for tube amp at all. There are too many tinkerers that modify tube amp to the Nth degrees. I left music electronics as of 1979 and only got back half a year ago where I don't work anymore and can afford to do for the fun of it for no money.

    When you read more schematics, you'll find all tube amp circuit basically evolved from one or two classic amps from the 50s. The Fender Bassman, Vox AC30 are two of those. Marshall pretty much Fender Bassman with a few value change. Mesa is just cascading a few of the preamp stages of Fender design to get the distortion. Their so called Simu cast is nothing more than combine different pairs of tubes in and out to reduce power.

    Learn the basics and read some of the schematics and you'll see what I mean.
     
  12. Apr 21, 2012 #11
    Thanks for the advice everyone! I think I've at least got some places to start now. I'll come back if I need more information/help.
     
  13. Apr 21, 2012 #12

    Bobbywhy

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    thegreenlaser,

    Just from the above comments I can count about 100 years of combined experience with this kind of equipment. Add in my 40+years and you have plenty of able and willing folks.

    You only said your amp was "acting up". Exactly what are the symptoms? Include as much detail as possible, and maybe we can help you troubleshoot it!

    Bobbywhy
     
  14. Apr 21, 2012 #13

    jim hardy

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    you need a multimeter and a tube manual.

    once you have figured out how tubes work, from reading the tube manual, you will know what voltage to expect at each pin.

    Then you measure voltages in your amplifier.
    Then you use laws of kirchoff and ohm to see what doesn't make sense.

    Google took me right to the service manual for a YCV50 amplifier

    but they interject themself in the link, i hate that
    http://www.google.com/url?sa=t&rct=...ptpJ_XPS740qlfIew&sig2=Q6FCrduCYvZrU58dnxp-uw

    i think you can download it from here
    http://www.traynoramps.com/default.asp?p1=7&p2=0&p_id=30 [Broken]

    http://www.traynoramps.com/downloads/servman/smycv50b.pdf [Broken]

    and it looks like a wonderful manual.

    Go man, GO !!!!

    old jim
     
    Last edited by a moderator: May 5, 2017
  15. Apr 21, 2012 #14

    turbo

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    Just between the two of us, we have over 80 years tinkering tube amps.
     
  16. Apr 21, 2012 #15

    Bobbywhy

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    My first radar set, the AN/APQ-72, was made by Westinghouse. In 1963 it was mounted in the nose of our F4B Phantom fighter jets. It was built with 100% vacuum tubes, and was remarkably accurate and reliable, considering. Often when the flight crew "griped" about some problem we couldn't duplicate it on the ground. So we would open up the radome, extend the radar set, lower each unit, and tap on the individual tubes with a screwdriver handle while one guy in the radar operator's seat monitored the 'scope. This simulated the in-flight vibration. Many times we could isolate the problem like this. We then replaced that unit, retested, and signed off the "gripe" as fixed.
     
  17. Apr 22, 2012 #16
    Thanks
    Now I got Traynor schematic in my collection.
     
    Last edited by a moderator: May 5, 2017
  18. Apr 22, 2012 #17
    Well, since I have all this experience offering to help me...

    The issue is specifically that it randomly cuts between normal-sounding and muddy sounding. (roughly every 30 seconds or so it will switch) If I use a volume pedal to keep the final output at the same volume, the effect is more noticeable when the master volume is higher.

    If I remember correctly, I tried re-seating all the tubes in case they were corroded or not connected correctly, but it had no effect.
     
  19. Apr 22, 2012 #18

    davenn

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    I would be starting off by looking at any of the electrolytic capacitors. They will dry out with time and give all sorts of weird faults. BE AWARE they are all rated for several 100's of Volts they do bite if not discharged!

    Dave
     
  20. Apr 22, 2012 #19
    Do you mean the channel switching or some sort of effect switching by itself? Find out exactly what function is switching and look at the schematic. If so, you might not have a tube amp problem, you might have a relay control problem instead. Some amp has LED to show the status of what your setting, does the LED switch also?

    If you want to, find the particular schematic of your amp from the pdf Jim Hardy posted, tell us what model is your amp. Test and find out exactly what function causing the problem and go from there. It is likely not the tube circuit at all, you might not have to learn the tubes.

    Does the "muddy" mode gets much louder? I remember Mesa has a tone circuit like Fender and they have a relay open the last leg to get a lot more middle ( muddier) but a lot louder for over driving. I am just guessing here without a schematic.
     
  21. Apr 23, 2012 #20
    I'm fairly certain it's not one of the switches turning on and off. It's definitely more like the clarity of the sound is just disappearing intermittently. I'll maybe check to see if I can replicate it by turning some of the tone knobs down all the way?

    @davenn how would I go about checking the caps? I'm assuming I could use a multimeter to check if they're charged, but how would I check if they're working?
     
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