Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Looking to get started. Silvertone Project

Discussion in 'Shock Brother's DIY Amps' started by tonyv77, Sep 13, 2017.

  1. tonyv77

    tonyv77 Tele-Meister

    Age:
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    253
    Mar 24, 2009
    New Brunswick, Canada
    ST1.jpg ST2.jpg ST3.jpg ST4.jpg Hey guys,

    I picked up a cool looking Silvertone "HiFi" Speaker Amplifier from a local guy for a crisp 20 sheet. Originally intended for record players I believe. Here's some specs:

    -It works!
    -6V6 x2 power tubes, 6AV6 driver, 12 AX7 inverter?, 5Y3 rectifier
    -8", 8 ohm speaker
    -RCA input (solder together an RCA to 1/4" cable to run my guitar)
    -No fuse, 2 prong plug :eek:

    The tube compliment looks close to some Fender stuff but I know the circuit could be completely different. I'm looking to get into amp modding (and light repair), not ready for building yet that's for sure. I know filter caps can be extremely dangerous and roughly how to work with them. I've modded a few pedals and can work a DMM and a soldering iron. My father also has some electrical knowledge (went to "radio college", worked on very early PC's, etc.) and is a resource. Any tips for starting out? Here's what I'd like to do:

    1) Add a fuse a 3 prong plug
    2) Check that the filter caps and tubes are good
    3) Swap the RCA for 1/4" input
    4) Add an internal speaker defeating external cab jack

    Here's some pics.
     

  2. tonyv77

    tonyv77 Tele-Meister

    Age:
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    Mar 24, 2009
    New Brunswick, Canada
    I guess this is a bit of a duplicate post from my discussion in the Glowing Bottle Forum. Sorry about that.....
     

  3. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    The 6AV6 is the input preamp. It appears to be a grid-leak bias input....hard to see the details. The 12AX7 is the phase inverter....hard to see but it looks as if it is a cathodyne PI. The output is cathode biased. You might compare this schematic to a 5E3 Deluxe.
    IMHO, falling off into changing this over to a guitar amp might be a daring move for someone who has never done any amp work....but....that seems to be the operative mode these days for many. Study the schematic. Go to Duncan Tube Data Sheet to learn the tube pinouts....that will help you learn to understand the schematic better. This could be a cool project, but some study prior to engaging might be advisable.
     
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  4. corliss1

    corliss1 Tele-Holic

    972
    Sep 13, 2008
    Lansing, MI
    Cool - any fender amp diagram using a layout should get you pointed the right direction on this. The hot side (the black wire of your new cord) goes to the fuse.

    The filter caps are not good. Replace them.
    If the tubes work and sound good, they are good. You don't really need to do any other testing than that.

    Both use 2 connections, although you'll likely use a shorting jack to eliminate hum on the input when nothing is plugged in. Check any single-input wiring diagram for this.

    Getting fancy here, huh? You can get the right jack that has internal switching (like maybe a Switchcraft 14B? I'd have to check a wiring diagram) that will break a connection when a plug is inserted.

    Measure DC voltage on the caps everytime you take the thing apart so you can be sure it's safe to work on. Good luck with your conversion!
     
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  5. tonyv77

    tonyv77 Tele-Meister

    Age:
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    Mar 24, 2009
    New Brunswick, Canada
    I've actually already played my guitar through this and really thought it sounded pretty good. I'm not stuck on making this into an old fender circuit. I like the idea of experimenting with something different. Just want to make it safer and make sure everything is running as it should. Might do a speaker swap, might not.
    There are plenty of great 5e3, 5f1, etc. kits, clones and mods out there that I don't really want to mess wit turning this into one. I do however see this as a launching point into my basic understanding of an amp circuit.

    Thanks for the pointers!
     

  6. tonyv77

    tonyv77 Tele-Meister

    Age:
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    Mar 24, 2009
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    Would it be easier to add a switch to go between internal and external speaker? I was thinking of that if there's space in the chassis.
     

  7. corliss1

    corliss1 Tele-Holic

    972
    Sep 13, 2008
    Lansing, MI
    Not really. The switch is just built into the jack, and once you wire that correctly you don't have to worry about remembering to switch it in 30 years when you aren't sure how it's wired :D
     
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  8. Karl Pilkington

    Karl Pilkington Tele-Meister

    206
    Nov 20, 2015
    Valley of Fire
    I use the neutrik-style switched jacks for external speakers on a combo.

    IMG_3605.JPG

    It's definitely preferable to having a switch.
     
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  9. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    The lower 12AX7 triode is a gain stage that feeds the upper triode which is a cathodyne phase inverter.

    Be sure and try a 25uF 25V cathode bypass cap on the 6AV6 input gain stage--you'll probably like it. You can temporarily alligator clip it on.

    Negative feedback is injected at the 12AX7 lower grid. Try the amp with that disconnected or tweak the NFB resistor to lower NFB to thicken the tone and make it less hi-fi.
     
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  10. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Fwiw, Tony, you will have to change quite a bit in that circuit to get away from the old Fender Deluxe type of thing...because that is what is sitting there.......something real close to a Deluxe from the late '40's/early '50's....pre-5E3 circuits. Check out the 5-A/B/C/D-3 circuits. Like it or not, the amp you have there is derived from the same circuits that Leo used.
    Leo Fender was a radio/TV repairman who used some basic Westinghouse circuits for his guitar amps. That is why we see that licensing of the circuit in the old tube charts.
     

  11. tonyv77

    tonyv77 Tele-Meister

    Age:
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    Mar 24, 2009
    New Brunswick, Canada
    Being a total noob I see that can type capacitors (3 capacitors in 1 can looking thing) can be upwards of $40. Would it be cheaper to swap in separate "modern" electrolytics? Keep in mind that this is purely an experimental tone toy/tool for my studio, not a restoration project (don't believe these things have any significant value). I'll leave them for now until I can complete some other mods (3 prong, fuse, input and output jacks).
     

  12. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    If there is room, individual capacitors are less expensive and also avail one of the ability to ground the circuit as one chooses.
     
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  13. corliss1

    corliss1 Tele-Holic

    972
    Sep 13, 2008
    Lansing, MI
    I wouldn't get too hung up on specific parts until you decide what circuit you're going with, but yes, if there is room you can use "regular" caps.
     

  14. tonyv77

    tonyv77 Tele-Meister

    Age:
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    Mar 24, 2009
    New Brunswick, Canada
    Not sure I'm going to decide on any circuit. The thing sounds pretty decently rad in its own right. But good advice to keep in mind.
     

  15. corliss1

    corliss1 Tele-Holic

    972
    Sep 13, 2008
    Lansing, MI
    If it sounds good, it is good :D
     
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  16. tonyv77

    tonyv77 Tele-Meister

    Age:
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    Mar 24, 2009
    New Brunswick, Canada
    Just got offered $125 for it. Considering the cost to retube and recap it, also the time (which I don't have) and other projects which need my attention (projects where I have actual know-how), I think I may let it go.

    HOWEVER, the knowledge given me in this thread is priceless. Probably will save me time, frustration, maybe my life in the future. I am very thankful to my faceless forum friends here. I tip my virtual hat to you.
     
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  17. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX

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