Tweaking the Bugera V5 Circuit

Discussion in 'Shock Brother's DIY Amps' started by tele_wah_fuzz, Jan 19, 2014.

  1. teleman55

    teleman55 Tele-Holic

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    This amps sounds real fine stock. I got one. It's my little at the house amp. I changed the tubes after a couple of years, that's all. Actually, I think it sounds better with the Chinese bugera tubes. Can't see a reason to mess with it. Nice amp.
     
  2. phildunph

    phildunph NEW MEMBER!

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    I want to clean up the amp with the negative feedback loop, but I'm having trouble understanding what a Output Transformer tap is and where to hook up the 22k resistor. Anyone can point me in the right direction?
     
  3. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The output transformer tap for the feedback loop is the speaker jack's tip terminal. I'm not familiar with your amp so I can't help with where to inject the NFB signal.

    If the V5 is a single ended amp with 1 power tube then you would normally want to inject the NFB signal into the driver stage tube socket cathode pin. The driver stage is the last amp stage before the power tube.

    I recommend a 3-way ON/OFF/ON mini switch so you can have two different resistors on the two switch end (ON) terminals for two levels of feedback. Leave the switch center (off) terminal empty so you can select no feedback in the center position.
     
  4. phildunph

    phildunph NEW MEMBER!

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    Thanks robrob!

    After a few google searches on OT Taps and what a NFL does, I figured it was the tip of the 4 ohm output!

    According to the OP's schematic, I wasn't able to locate exactly where the for the NFL would originate from, so I took a wild guess at a junction of R20, C13 and their distance from the 12AX7 tube socket. And the results weren't bad!

    Although, I still want to try and clean up the amp. Still breaks up too early for me, compared to my Champ 600.

    I did replace the speaker with a spare Jenson Mod/8 I had, which is 20 Watts. Do you any of you interested think it's breaking up too early because of the speaker?
     
  5. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    I just removed C22 and C13. Nice improvement. I'm waiting for mail im parts for the bright caps and NFL. I want to pit those on a switch and install a variable NFL resistor.

    I was wondering if I'd need a high watts resistance or a simple 1/4W would do?

    Next is the 820h.

    Thanks
     
  6. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    By the way, how do you drain those filter caps. I found that they can be drained by shorting some diodes from the bridge but do you have a simpler way? I tried to short the el84 plate to ground but I still have 18V in the caps.
     
  7. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    Reporting back!! I just fired up my upgraded V5. What a difference. I removed the 2 caps but put the bright caps on a switch and installed a NFL on a 10k/off/1M switch with a 50k pot. I like to keep the stock sound, just in case.

    It sounds great now

    To be honest, the pot does nothing but the NFL switch is great to clean up the amp.

    My bright switch gives me plenty of highs with a nice boost. With that setup it's easy to A/B the changes.

    I'll keep the stock speaker for a while.

    Thanks to Tele wha fuzz for the diagrams.
     
  8. MikeJackal

    MikeJackal TDPRI Member

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    Sorry for resurrecting an old thread but I only just discovered it as I recently bought a Bugera V5 Infinium and found it rather dull.
    I only did the first mod removing cap 22 & 13 and now although the tone is much brighter (still on 10 though) I have no reverb at all.
    Have I messed my amp up by doing a mod on a newer model or something?
    Many thanks in advance for any advice.
     
  9. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    Did you look at the values of those? I haven't seen the infinium schematics. The components might not be numbered the same way. On the other hand, SMD boards are very sensitive. You might have briken something else.
     
  10. MikeJackal

    MikeJackal TDPRI Member

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    No I'm a tit and prone to spontaneous gun-jumping.
    C22 was a tiny little rectangle thing that had no readable writing on it set among many other tiny rectangle caps.
    C13 was a can type, 10uf 50v.
    I've buggered it up haven't I.
     
  11. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    ImageUploadedByTDPRI1445545544.664749.jpg

    You might have renoved the wrong one. C13 is 2u2 50v but there's C17 witch is 10u 50v electrolitic in the reverb circuit. Those are the original V5 numbering of course. It can be repaired but you'd need to find out what you removed.

    Of course the circuit and values might have changed and I might be wrong.
     
  12. MikeJackal

    MikeJackal TDPRI Member

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    I will put the 10uf back and see what happens.
     
  13. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    Carefull with the polarity
     
  14. MikeJackal

    MikeJackal TDPRI Member

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    Indeed, always good to be reminded of that. Well I put the cap back and the reverb is working again so problem solved. The small cap I removed has helped with taking that wet blanket off.
    I will do the caps on the control pots and leave it at that.
    Thanks for your help Chuck.
     
  15. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    You can find the 2u2 50v cap. It should be near pin 8 from the 12ax7 negative side to ground. There's not many electrolitic cans in there besides the bigger filter caps. But your right, it's not the biggest difference mod, the bypass caps do the real job there.
     
  16. J-Bone1978

    J-Bone1978 NEW MEMBER!

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    Bright mod switch

    I installed 220pf caps across the volume and gain pots. For me, this was enough. Love the sounds I can get now! However, I would like to be able to switch the mod on and off. Anyone know how to do this? Appreciate any help.
     
  17. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    I installed a 3pdt switch at the rear. Simply solder a pair of wires at the same place you wired your caps. One wire to one side of the switch and the other one to a lef of a cap. The other legs goes to the switch. Just be carefull to protect the bare parts of the wires like the legs of the caps. I kept them as short as possible and put some shrink on it. You could do it with some terminals or a small board but it's as simple as that.

    You could also use 3 switches and try one cap at the time.
     
  18. dimitris74

    dimitris74 NEW MEMBER!

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    hey guys, complete amateur here, just wanted to ask, what kind of 220 pF bright caps should I buy? Ceramic disk, electrolytic, soZo?? I'm new at this. Thanks
     
  19. rone

    rone NEW MEMBER!

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    Hi guys!

    I was stoked when I read about this mod so I grabbed my soldering iron and proceeded! I removed C22 and C13 and added the caps across volume and gain pots.

    Unfortunately, while my amp does sound brighter, it has also lost almost all of its gain. So I removed the caps across the pots but no improvement.

    I used to have a really nice crunch with the gain pot a little past noon. Now I have to crank it up all the way and the sounds barely gets saturated. If I set the gain to 3, I can barely hear any sound coming out of the amp.

    I have two sets of tubes, so I know it doesn't come from them.

    What could I have possibly messed up? I'm decent at soldering things, I don't think I damaged the circuit... or at least I can't see it!

    Does someone have photos of the mod?

    Thanks a lot for your help!
     
  20. CHUCKHDTV

    CHUCKHDTV Tele-Holic

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    Are you working on the original or the infinium version?
     
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