Unorthodox RR800V Build

Discussion in 'Shock Brother's DIY Amps' started by NSB_Chris, Mar 28, 2020.

  1. NSB_Chris

    NSB_Chris Tele-Meister

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    I have been planning another RR800V Build for some time now. The original design from Rob Robinette was posted here:
    https://www.tdpri.com/threads/jcm800-6v6-6l6-el34-in-a-princeton-reverb-chassis.947374/

    Some thoughts that went into this build:
    • I wanted to have the option of adding time based effects after the preamp distortion, so I added a tube driven effects loop that can be fully bypassed in case I hate it. https://www.tdpri.com/threads/tube-driven-effects-loop-and-other-questions.1006952/
    • I wanted to be able to have the amp head close to my pedalboard for easy access to tweaking and short cable runs for 4 cable method. My thought was I could put the speaker cabinet wherever with the only long cable run being the speaker cable. This led me to an unorthodox over/under split chassis with knobs accessible from the top. Not a friendly configuration to build, but I took a shot at it.
    • I wanted the inputs on the front side and the power and speaker on back.
    • The main circuit is pretty much the same as the one I built previously in a Fender Twin cabinet. Two channels mixed in with 270k mixing resistors. No internal switching.
    • I was originally going to try some channel switching, so I shoehorned in a DC power supply to be driven off of the 6.3V tap or the unused 5V tap. I abandoned the channel switching but kept the power supply in case I change my mind later. It just drives the pilot light at the moment.

    The power chassis is on the bottom and the chassis on top has the preamp and effects loop. I am running wires between the upper and lower through copper conduit. One for heaters, one for B+4, one for preamp line out and one for the ~5V DC power supply. I will add a picture of the chassis assembly that is taking shape. The volumes and tone stack knobs will be on cover strips on the top chassis (not drilled yet).

    Wish me luck!

    IMG_3712.jpg
     
    D'tar and shortcircuit like this.
  2. boredguy6060

    boredguy6060 Poster Extraordinaire

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    Very interesting!
    Love to hear it, and see it when you’re done.
     
  3. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Very cool. Subscribed.
     
  4. NSB_Chris

    NSB_Chris Tele-Meister

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    Making progress. I think the chassis is ready for paint on the surfaces that will get water slide decals, two main chassis boxes and the control plates which are now drilled. Boards are drilled and ready for turrets. Time to pull everything apart and get prep for paint.

    IMG_3714.jpg
     
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  5. NSB_Chris

    NSB_Chris Tele-Meister

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    Paint is going on. In between coats, I have another unorthodox aspect to discuss. One thing I am implementing on this build is a "master volume trim". When setting up for high preamp distortion, the volume/gain pot is near 10, so the MV is at the bottom and very twitchy. I am adding an extra trim pot that I hope will give more control at the bottom of the MV setting. I am guessing a 5K pot will give the control needed. With the MV pot all the way down, the 5k pot controlls the last 5k of resistance. With the MV above zero, the trim will have negligible affect. Thoughts?

    Here is my preamp circuit:

    RR800V II Preamp V01.jpg
     
    Last edited: Mar 29, 2020
  6. NSB_Chris

    NSB_Chris Tele-Meister

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    I have heard people say they like Krylon paint and now I see why. Krylon was not convenient to get at stores close to me so I went with Rust-oleum on previous builds. This one I got Krylon and wow, what a difference! I will always use Krylon from now on.

    Had one hitch. When I drilled the turret holes in my large preamp board, I accidently grabbed a larger size drill bit ... stupid! They were a little loose in the hole, but with a firm swage on the turrets, I think they are all sturdy.
     
  7. NSB_Chris

    NSB_Chris Tele-Meister

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    Let the base coat dry for 48 hours and slid on the water slide decals. Ok job, not great, but functional. I will let those dry for 24 hours and then start the clear coat regiment. Have to do a final pass at error checking the layout before populating the boards and loading the components.
     
  8. NSB_Chris

    NSB_Chris Tele-Meister

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    The ink on some of the water slide decals got damaged on application and I don't think my clear coats went on very well. Not my best work but it will do. This one is going to look road worn before it has any tubes glowing. I think next time I am going to put a coat of clear on the sheet of water slide stickers before I cut them out. Well, components are starting to go on. It will be a few days until I can get back to the boards etc.

    IMG_3723.jpg
     
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  9. NSB_Chris

    NSB_Chris Tele-Meister

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    Taking shape. Main components mounted and heaters run between all of the sockets. The 9 pin socket shield cans are added just to show location and that they don't interfere with components on the other chassis side. Side panels and handle bar will be wood with black tolex, but I have not started them.

    IMG_3727.jpg IMG_3728.jpg
     
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  10. BigDaddy23

    BigDaddy23 Tele-Holic

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    Fantastic looking build there mate! I'll be watching with interest.

    On ya decals, it's best to hit the straightaway with a good coat of clear after they come of the printer. This 'sets' the ink and prevents any subtle bleed whilst they are in the water and protects them from damage during application. You've done a really professional looking job though.....I don't mind the roadworn look.
     
  11. NSB_Chris

    NSB_Chris Tele-Meister

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    Thanks! This is meant to be used and not intended to be a show-piece, but it can be frustrating when things like that happen. Early blemishes has the benefit of not having to worry about protecting it from everything. :) There are some other areas, like I cut a square hole for the power plug socket thinking that the flanges would cover, and they didn't. Oh well, additional unintended ventilation!
     
  12. robrob

    robrob Poster Extraordinaire Ad Free Member

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    That looks crazy cool.
     
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  13. NSB_Chris

    NSB_Chris Tele-Meister

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    A little more progress today on the power amp side. I prepped the boards and did some wiring in the power amp chassis.

    IMG_3733.jpg
     
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  14. NSB_Chris

    NSB_Chris Tele-Meister

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    Some progress. Staying close to relatives for the pandemic so have limited access to my amp building area. Spent some time populating the power amp chassis boards and getting them ready to install. Still making small change decisions and finding small errors in my documentation. Also ran out of solder right at the end of today's work. No matter how much planning I do, I always find a few things. Going to spend some time updating my layout drawing and purchase some solder. Probably right as the order comes, I will find something else that I didn't order. Comes with the territory I guess.

    edit: Looking at the photo I posted below, the iPhone camera did some weird perspective things that make some of the components look strange. The mini-pots I sourced for the bias section are the same dimentions, but the balance pot looks thin and the level pot looks square.

    IMG_3742.jpg
     
    Last edited: Apr 19, 2020
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  15. NSB_Chris

    NSB_Chris Tele-Meister

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    In updating my layout, I see some big errors that I corrected a long time ago and were not in the printed sheet above. I should not have posted that layout. I will post one later that is better.

    Also, in reading other posts, I see I could have tested the outer foil orientation of the capacitors. I should be able to check the ones that are in the board now since the board is not completely wired in. Probably does not matter in the power amp section but leave nothing to chance! I will check them for the preamp circuit for sure.
     
  16. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The outer foil is only a concern for non-polarized caps like your coupling caps. Even then it is a minor concern. I do my caps because it's easy and it can't hurt.
     
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  17. NSB_Chris

    NSB_Chris Tele-Meister

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    With the pandemic, I have limited access to my shop, so progress is going to be slow. Spent some time with the power amp section this past weekend. Picture below. Getting close to firing up the power amp section to test some voltages.

    I am scrapping my preamp board. Earlier in this thread I noted that I stupidly selected a larger bit size for drilling the turret holes. At first I thought that I could swage them and it would work. After finding a few loose turrets, I am worried about them loosening during soldering or later, so I will remake the board. Bummer! Going to use the opportunity to move some things around a bit.

    I have done a few error check runs but need to do a thorough check soon as I have made some adjustments. Hope to get back to soldering in a week or so!

    IMG_3751.jpg
     
    Last edited: Apr 28, 2020
  18. tubegeek

    tubegeek Tele-Holic

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    Classy chassis. That is some very fine metalwork.
     
  19. NSB_Chris

    NSB_Chris Tele-Meister

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    Have had some time to devote to this project yesterday and today. The preamp board is now wired and installed. All that remains is resistors for the pilot and chassis LEDs. Not going to put the top control plates on until I have at least checked voltages with the tubes out. Now its time so trace every wire, component and connection and verify against the schematic. Hoping I find all errors that may be lurking and that whatever I find I can easily fix. There are some really tight areas in this!


    IMG_3771.jpg
     
  20. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    Very, very nice!
     
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