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Rivera Boost Mods - R55

Discussion in 'Amp Tech Center' started by soundchaser59, Jan 12, 2014.

  1. Ike286

    Ike286 Tele-Holic

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    Hmm, placing shield grounds can be "fun" sometimes... I usually like the pot housing, but find a good chassis ground near the pot (pot included) and dont connect it to a ground that is for a cathode, or a volume/tone control, because in my experience, those things can cause noise issues etc.

    So I'm not sure what the layout of your amp is, but the pot housing should be fine. You shouldn't need any flux, just take some 220 or so grit sandpaper and sand the back of the pot where u intend to solder onto, and it works awesome.

    Make some clips when your done too! Hope it works out well. :)
     
  2. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    A good tip for drilling the chassis is to stuff a bottle screwtop lid with playdough,( or what ever one calls that funny tasting putty stuff that kids play with) and press this up hard against the inside of where the drill is going through, all the metal shreds and bits get stuck in it. Put a small coin in the bottom of the screwtop under the putty, the push this against the drill direction your thumb. This way you get good pressure to drill, no hole in your thumb, and don't shoot through the chassis hitting other components with the drill when it breaks through. A bit of this putty on the end of a pencil is a great way to pickup any bits that might get through. Small snippets of wire and solder droplets are also best caught this way.
     
  3. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    "Careful desoldering makes it a lot easier to work on this thing from the top, cuz I really really don't want to take the board out of the chassis. "

    Wait a minute, you've got me worried now! If you don't want to take the board out so you can desolder the leg of the optocoupler, lift it up, and insert the new wire running to the poti, and resolder it properly, as is the best way to do the job. It seems then you intend to do the whole job from the top. This is okay, but a better way is to first melt a small blob of solder onto the bottom of the leg you intend to cut as a holding and mounting point, solder on your new wire, and then cut the leg in half, leaving a bit of the original wire poking up out of the hole allready attached. This way round you dont risk the small bit of wire falling through if you melt the solder on the bottom. Trying to resolder from the top into a clean hole is likely to leave you with a dodgey or dry connection in my opinion, it might work, but then again it is not as safe as doing it the other way.
    Maybe I misunderstood what you intended to do, but I thought I had better point this risk out to you.
    The potis will get grounded through thier contact to the chassis. The sheilding for the wires to the optocoupler can be the taken from the back of the poti.
    Judging from the measurments from the poti you gave, it sounds like they are log potis, and not linear. Use the, from the back seen, the left hand and the middle tag. If you are not happy with the results, change them later to linear, but if you are not constantly changeing the setting, but happy to find the sweet spot and leave it, then log will work.
     
  4. Ike286

    Ike286 Tele-Holic

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    Never thought of that, although I'm usually just careful not to pop through and hurt anything, with my amps, usually they are layed out in a way that I turn the chassis one way, and then it all falls out... Maybe I'm just lucky!
     
  5. soundchaser59

    soundchaser59 Tele-Afflicted

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    I had my wife hold the vacuum nozzle next to where I drilled. I drilled from the inside, there is an open spot on the chassis right behind the input jacks. I put a thick cardboard box underneath (next to the preamp tubes, and under the fx loop pots) so when the bit broke thru it simply put a hole in the box. Vacuum kept the inside chassis clean. There is enough room for two pots side by side, so I bought another pot and I'm going to make both boosts variable. I'll do the Ch.1 boost mod first, since it seems to be more difficult.

    When I replaced the screen and grid resistors a few months back, I did all of that work from the top, desoldering and resoldering, worked fine. I'm not a great photographer, but I'm trying to take some pictures as I go, and I'll show you what I did.

    The leg of that vactrol looks like it's in there pretty good. It will require some very thorough desoldering, but once it is loose I think I can work it up out of the hole with my mini needle nose and a sharp needle point probe. It looks like it's the same gauge lead as the resistors.

    Bendyha, that photo you posted with the red circle.......the mod doc I got from Marshman says to lift the vactrol leg that joins with the junction of R130 (2.2M) and R119 (100K). Your photo actually shows that junction! R119 is the light blue resistor just behind the gray wire just above the top of your red circle. (hard to explain) Anyway, your photo actually shows the solder joint of the leg that has to be lifted! There are 3 solder joints right there, all in a small group, and that's the junction of PH106+R119+R130.

    I'm going to remove R130 first (to make more room to work) because under the magnifying glass R130 appears to be slightly scorched and overheated, so I will replace it with a 2.2M 1/2 watt R. That will give me plenty of room to work on the PH106 leg lifting.
     
  6. soundchaser59

    soundchaser59 Tele-Afflicted

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    Nothing ruins a fun job like having piece of ***** tools. I'm so freaking frustrated with this piece of crap soldering iron right now I feel like I could turn a car over with my bare hands. I knew this soldering iron would be the kink in my work flow.

    What was it Rainman used to say all the time......"Radio Shack SUCKS!"
     
  7. Ike286

    Ike286 Tele-Holic

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    Haven't used my weller in a while, because of having a nicer one, but a weller iron is a nice tool... Even the cheapest basic one, like I have. I've even used it on pickup repairs etc, with those teeny tiny wires.
     
  8. soundchaser59

    soundchaser59 Tele-Afflicted

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    Well, it was blind luck. I accidentally grabbed the "solder wick" and it wouldn't remove any solder if my life depended on it. Then my soldering iron wouldn't even melt the solder at the solder joints on the board. (but it would melt fresh solder touched to the tip just fine)

    So when the dog started snooping around in my tool box, I said, "Get outa there, that's not for a dawggie!" When she moved I saw my other roll of "de-soldering wick" in the tool box, tried it and the solder immediately got removed from the board. (what's the difference? solder wick vs desoldering wick?) I guess the dog knew what I really needed.

    So I desoldered the leg of the vactrol, and what do you suppose happened next? It broke off! So I thought I was completely f*u**k*d. Then I realized there was still an 1/8th inch of lead sticking out there, so I put a slight curve on it, made my wire end into a hook, and used tweezers to clamp them together. A quick touch with a drop of solder and it held.

    I haven't tested anything yet, I'll get to that later today. I guess it's only blind luck if the darn thing still actually works when I turn it on. If so, then the Ch.1 boost mod is done. I'll keep you posted.
     
  9. soundchaser59

    soundchaser59 Tele-Afflicted

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    Came home quick for lunch, and........

    IT WORKS! :twisted: :cool: :D

    more later......I'll do the Ninja side mod tonight.
     
  10. Ike286

    Ike286 Tele-Holic

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    Again, make sure to post video/audio clips. I'd love to hear em.
     
  11. soundchaser59

    soundchaser59 Tele-Afflicted

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    (sorry about my poor photo skills)

    Holes drilled....
    [​IMG]

    Continuity for PH106 to the junction of R130 and R119....
    [​IMG]

    The two pots mounted to the chassis, just behind the input jacks....
    [​IMG]


    Leads attached to one leg of PH106 (vactrol)......R130 (2.2M) is replaced and new, the old one appeared scorched.
    [​IMG]


    R117 lifted at one end (the blue resistor standing up straight), a piece of resistor lead in the other hole, make a hook in both ends, and attach the leads for pot #2 Ninja adjust to the hooks.
    [​IMG]

    Both sets of leads in place, with shrink wrap for stability....
    [​IMG]


    the pots again, now attached to the boost circuits.... I will set to taste and leave it alone.
    [​IMG]


    If I were going to do it again, I would use 2M or maybe even 4M or 5M ohm pots. These 1M ohm pots are not quite enough ohms to completely nullify the boost. I still get a small boost even with the pots on full resistance (full counter clockwise). In fact, it's almost the perfect amount of boost for my taste, with the pots fully engaged. Full clockwise gives me the original over the top boost level.

    I'll make some audio clips in the next few days. We are going out of town soon, but I will post some audio, so be patient.

    And.... THANK YOU ALL for your assistance! You guys ROCK! :cool:
     
  12. Ike286

    Ike286 Tele-Holic

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    Looks good! You made it look easy.
     
  13. soundchaser59

    soundchaser59 Tele-Afflicted

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    I recorded a short demo of the changes, I'll try to get that posted tomorrow evening. I recorded a bit on both channels, no boost, the original boost, and my adjusted boost, and I'm pretty sure you'll be able to tell the difference. I'm totally convinced now that this is a very necessary mod on these amps. I believe the Knucklehead also would benefit greatly from this same mod. (There is a Knucklehead 55 for sale right now, and I can't afford it. Darn It! That K55 was my all time favorite amp!)
     
  14. marshman

    marshman Poster Extraordinaire Silver Supporter

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    I don't recall where I read it, but I know I'd read that someone put those on the the back panel by removing the fx loop they never used.

    But nice looking work, no doubt.
     
  15. soundchaser59

    soundchaser59 Tele-Afflicted

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    Didn't even occur to me to do that. I put a lot of effort into getting replacement fx loop pots and knobs from Rivera. Those pots were smashed in and useless when I got the amp. Love me some fx loop, but right now I am only patching it so I can experiment with using the pots as a sort of global master volume.
     
  16. soundchaser59

    soundchaser59 Tele-Afflicted

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    Here is a 40MB wav file that demonstrates the change to the boost levels.

    http://www.soundchasermusic.com/demos/rivera_boosts.wav

    Download it before you play it, as wav's tend to not stream very well.

    Here is roughly what you are hearing...... I like to push the gain to the edge just before breakup, so my "clean" sound is not crystal sparkly clean like you may expect.......but the Rivera amps will do a crystal sparkly clean if you desire it. :cool:

    ch2 clean (boost off)
    ch2 adjusted boost (about 1/3rd of the pot's range)
    ch2 full boost turned up, then back off
    ch2 clean
    ch2 adjusted boost

    (approx at 2:07)
    ch1 lead no boost (boost off)
    ch1 lead adjusted boost (boost on, but pot fully counterclockwise)
    ch1 full boost (pot full clockwise)
    ch1 adjusted boost
    ch1 no boost
    ch1 adjusted boost

    You should be able to easily recognize when the full boost level is on, it's pretty clearly different than the rest of the sounds.

    No fx, no OD pedals, no processing, just the raw wav recording, reverb is the 3-spring tank in the amp, fx loop is patched with Send = 7 and Return = 3, JJ 5751 in the V1 slot, Weber Amsterdam speaker, EV BK1 + Sennheiser E906 mics on the grill at speaker edge, this is a G&L ASAT Z3 telecaster.
     
  17. redeyedjim

    redeyedjim TDPRI Member

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    Just wanted to post a thank you note to the contributors to this thread for the excellent writeups, pictures, and willingness to share. I just completed modding both boosts on my Chubster 40 based on the descriptions in this thread (and a companion thread at TGP), and the mods turned out great!! Thank you! It's wonderful to finally have useable and adjustable boosts on both channels -- it improves the amp dramatically.

    Thanks again!
     
  18. Ike286

    Ike286 Tele-Holic

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    As always... You are welcome. I hope I was helpful, and that you learned something. I know I always learn something new when I'm fooling around... :)
     
  19. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    My pleasure.
     
  20. soundchaser59

    soundchaser59 Tele-Afflicted

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    Glad you got it done well!

    Of all the different sites and forums I went looking and asking for help, this is the one that finally made it possible for me to actually do these mods on my amp.

    ++++1111111
     
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