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Peavey Bandit 112 (USA) to custom job...but what?

Discussion in 'Shock Brother's DIY Amps' started by dougsta, Jan 20, 2021.

  1. dougsta

    dougsta Tele-Meister

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    So last January I picked up this nice Peavey Bandit 112 USA Sheffield combo, worked ok except for some of the pots were busted and the normal input jack was looser than a !censored!
    It also came with 2 guitars, an 80's strat copy with no strings and a cool 60's 4 pickup Japanese curiosity, the guy was happy with £20 as he didn't play guitar and didn't know how to fix them.

    It's all stripped down and waiting to be transformed into a nice custom job tube amp.

    The chassis is 9 1/2" x 21" x 1 7/8" nice n roomy but the aluminium sheet is quite thin.

    Speaker works nice.

    I tested the long spring line reverb tank (ss higher impedance type) with a tube drive circuit similar to a '63 fender reverb unit and sounds great.

    The cab is solid and heavy, I'd like to change the speaker grill to a 60's fender look.

    I've unwound the power transformer and can reuse the laminations/end bells and rewind it to custom values.

    Tube I have in the octal drawer:
    4 x EL34
    8 x EL84
    2 x 6L6GC
    11 x 6V6
    6 x EL36 (Russian type TV line drivers, these can put out some serious power eg 60W form a pair - top cap anodes too)

    The OT will depend on whatever power tubes are used.

    But what to build, a Deluxe Reverb inspired comes to mind.

    What do you think?
    IMG_7816.jpg
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    Doug.
     
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  2. dougsta

    dougsta Tele-Meister

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    Here's the 1960's Japanese guitar I got for free with the £20 amp.

    IMG_7049.jpg
     
  3. stepvan

    stepvan Tele-Holic Silver Supporter

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    I like how Tiesco always had something crazy going on with pickup configurations
     
  4. Drew617

    Drew617 Tele-Meister

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    Robinette Blackvibe 6V6? I haven't heard 6V6 or 6L6 versions, but have built a Micro and that's an excellent, juicy BF circuit. With Reverb and Trem delete it should be simple enough to build and allow some flexibility in an oddball chassis, and keep you from having to punch too many holes in it.

    Funny enough, I have access to a 110 Peavey cab and chassis and have considered that for a conversion. Were it me, I would leave the cosmetics alone, including unused pots/knobs on the front panel. Those Transtubes were not at all bad for what they were, but you could build something much better and more entertaining in there. Adding Fenderish touches might turn it into kind of a bastard, where allowing it to look exactly like a Transtube Peavey makes it a legitimate sleeper.

    IMHO, of course. :)
     
  5. dougsta

    dougsta Tele-Meister

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    All ideas welcome :)

    I do have plenty of those Russian 6V6 to use up, could put 4 in there and have a bias switch to enable to run on 2 or 4 tubes, would need to pull 2 tubes (one from each side) out.

    I was also wondering what to do with the front panel, I could keep it original and have 2 channels, I also can use the reverb tank and keep the reverb control. I kept the relay components, need to test them 1st, so could add channel/reverb switching.

    I don't mind going full custom hot rod.

    Doug.
     
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  6. Jakedog

    Jakedog Telefied Ad Free Member

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    I always prefer anything EL34 based. So that’s my vote.
     
  7. jvin248

    jvin248 Doctor of Teleocity

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    .

    I would have repaired the Peavey Bandit, I much prefer them to tube hassles .... but since you stripped it already:

    And I'd make it as a head with cabinet system so you can use different speakers/cabinets anytime.





    Redo the Teisco 4-pickup guitar to get it running again. Cool tones and vibes from one of them.
    You'll likely need to level the frets and/or replace them (if so then go stainless steel). Keep the zero fret system.

    Get the 80s strat copy running and rewire with an Armstrong Blender mod (SSS blends to HSH) as that will make it a lot more fun to play.

    .
     
  8. dougsta

    dougsta Tele-Meister

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    I did a setup on the Tiesco, frets were ok, I put a shim in the neck pocket to give it a slight break angle. The main issue is the bridge, it was at right angles to the strings with no way to set intonation, I set it at slight angle to get it closer. Lots of contact cleaner on the pots and switches.
    It needed a good clean too, bit of rust too but it is quite old.
     
  9. dougsta

    dougsta Tele-Meister

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    It's nice to have so much space inside, will be better once I move the power cord entry point and panel mount fuse holder to the rear panel, just trying some layouts.

    IMG_7826.jpg
     
  10. mkdaws32

    mkdaws32 Tele-Afflicted Gold Supporter

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    I’d go with a Marshall style preamp with a pair of EL34s. An SC20 112 combo (JCM800 20 watt). Would sound killer with that Sheffield.
     
  11. dougsta

    dougsta Tele-Meister

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    Here's a different way to arrange the chassis, any issues with it?

    The 4 octals don't have to all be populated, could just run with a pair, add bias adjust pot and switches to enable running with a choice of 6V6, EL84 (extra 9pin bases wired to each octal), EL34 or 6L6GC and use the 4 Ohm OT tap run into an 8 Ohm speaker trick.

    The transformers are just there to see how they would fit, the PT in the photo only has a 3A heater secondary, the HT is 260V @ 350mA and the bias 25V @ 250mA (would need a voltage doubler)
    I plan to wind a custom PT with added taps for a range of final DC B of, eg 150,300 and 400V

    Doug
    IMG_7842.jpg
     
  12. zeppelinofled69

    zeppelinofled69 Tele-Meister

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    That layout reminds me a lot of the way that Hiwatt and Soldano did things... Main difference I see is the preamp tube sockets went between the front panel and the board instead of the components flying directly over the sockets, but I don't see any issues with the potential layout.

    Will you be using a choke?
     
  13. dougsta

    dougsta Tele-Meister

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    Thanks for the info, I don't have a schematic yet so I thought I would go with a 'evolving' build, I expect a lot of changes along the way and some suggestions from the guys here.

    The tag strip allows a lot of ideas to be incorporated along the way and it will end up more like a point to point build.

    Good call on the choke, you reminded me to have a look through my stash of bits and found a brand new boxed Hammond choke I planned to build a deluxe reverb with, also found a Hammond reverb transformer too.

    I'm planning to incorporate the '63 Fender reverb unit circuit in the combo and maybe try to have it controlled by a foot switch and relay. I have had some good results with a transformer-less tube reverb driver in my 6V6 SE champesque amp, I could build both types and compare them. I have low and high impedance tanks.

    Doug
     
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  14. zeppelinofled69

    zeppelinofled69 Tele-Meister

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    Interesting idea on the 6G15 reverb being in the same chassis... Are you going to mod the circuit at all? Or perhaps put a switch in to bypass it when not in use? I believe there is a gain stage that the signal always passes through on that circuit even if the reverb effect is disabled.
     
  15. dougsta

    dougsta Tele-Meister

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    My current planning stage ideas (maybe too much crazy stuff going on!):

    I have a JCA22H (Soldano design, Chinese made) head 4 x 12AX7 and 2 x EL84, it has a tube buffered effects loop, I'd lift most of the design from it.

    2 channels, clean and overdrive.
    Clean channel would be V1a/V1b with a gain, TMB and master vol, overdrive channel would get the same with an extra triode stage. Foot switch/relay to swap between channels.

    Reverb via send/return buffer, foot switch/relay to bypass.

    B+ voltage selection via 3 way rotary switch, Low 100-150v (depends on the right brown-out type sound) 300v for the 6V6/EL84 and 400v for the EL34 and 6L6GC.

    Bias adjust knob to set bias depending on tube and how hot you like 'em.

    Output impedance switch, eg 4/8/16, the current speaker is 8 Ohms, if I run with 4 tubes then select 8, if I run with 2 tubes select 4 into the 8 Ohm load, 16 if I run to an external speaker.


    Doug
     
  16. zeppelinofled69

    zeppelinofled69 Tele-Meister

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    That sounds like it's gonna be a very feature-packed amp.

    I like the idea of the reverb in the existing FX loop. My only comment here is to put the reverb at the recovery end of the loop so if you add other time based things, they go through the reverb last and then back into your FX recovery stage.

    Since you like options... you might even be able to work it out so you can switch the reverb to be first or last in line on the FX loop connections... hmmm :D
     
  17. dougsta

    dougsta Tele-Meister

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    So, today the donor power transformer parts from the Peavey SS amp was mutated (lams and end bells only) into a tube amp PT :)

    I entered the size of the core (width of E plate tongue x height of lams stack) into my tube amp power transformer program and then added the windings I required (for taps, leave the current required blank)
    I've gone with an HT with multiple taps 0-120-220-360v @ 160mA, a bias supply of 50v @ 10mA and 2 x 6.3v at 3040mA (enough for 4 x EL84) and 3000mA (I entered these at 6.9v to account for the voltage drop under load). I plan to add a voltage drop feature to my app to calculate this based on the length of wire.

    new power trans.jpg

    It's wound and assembled.

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    5lb or 2.3kg

    I measured the ac voltages with no load on the HT and bias, today my mains voltage was a wee bit lower at 235v (should be 240v)

    0-120-218-359 and 48.5v

    So close enough, might have been spot on if the mains was at the usual 240v.

    On the heaters side, I measured the ac voltages without a load and with the load of a single EL34 drawing 1500mA (as per data sheet)
    1) 6.87v no load and 6.3v under load
    2) 6.86v no load and 6.2v under load

    So all good :)

    Doug.
     
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  18. MatchlessMan

    MatchlessMan Tele-Holic

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    Subscribed! This is right up my street. Since the pandemic hit I have scratch-built 2 valve amps and a 6G15 clone and re-built a modern PRRI to hand-wired blackface spec. I am currently waiting on delivery of a busted Line 6 Spider combo to convert into a single-ended 6L6-driven amp.

    I have previously built on turret board or eyelet board, and I’ve used tag strip for an add-on reverb drive/recovery circuit. I’m considering trying it on the SE build.

    Transformer winding is well outside my skill set though. I have had some luck sourcing inexpensive transformers and recycling existing ones - potentially the biggest cost in amp building.
     
  19. dougsta

    dougsta Tele-Meister

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    http://primarywindings.com/ do a nice 10W SE output transformer, only £30 ex p&p.
     
  20. MatchlessMan

    MatchlessMan Tele-Holic

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    Thanks for the link, that’s very useful! I’ve already got a suitable Hammond OT but there will of course be other projects...
     
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