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SS/Tube rectification for 18 watt 1974x

Discussion in 'Shock Brother's DIY Amps' started by Sam VanLaningham, Mar 1, 2021.

  1. Sam VanLaningham

    Sam VanLaningham Tele-Meister

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    Hello Shock Bros - Hoping you can help me rectifying this 2nd 18 watt tremolo Ive built. I would like to, at the least, add backup diodes and ideally add a SS/tube rectification switch ala a famous modder known to frequent these hallowed servers......

    So we have Robs ss/tube for 8 pin rectifiers in fender amps:

    upload_2021-3-1_20-56-34.png

    Then we've got the traditional 18 watt tremolo 1974x layout with its 9 pin rectifier....and then this 9 pin backup diode layout from Rob:

    upload_2021-3-1_20-57-58.png

    Finally, ramblefx.com gives me a little idea of how a ss/tube switch might work with the 9 pin tube. Then next to that I post what I hope is a functional layout for ss/tube and backup diodes for the 1974x circuit. Will this work?

    upload_2021-3-1_21-2-21.png
     

    Attached Files:

  2. Sam VanLaningham

    Sam VanLaningham Tele-Meister

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    4FB00804-E198-488C-8665-9F5935E47C71.jpeg Ok bump anybody got thoughts on this ss rectifier layout for 9 pin rectifier sockets?
     
  3. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Yes you can.
    The B+ will be higher with the SS rectification but as long as the bias is ready for the higher B+, it should work fine.
     
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  4. Sam VanLaningham

    Sam VanLaningham Tele-Meister

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    @Lowerleftcoast Thanks LLC. Do you have any concerns that i will nuke PT or tubes with the particular wiring layout that, scarily, i drafted here:)?
     
  5. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I will have to qualify my answer...
    If the switch works the way I (we) think it does, this will switch between the Tube (with backup diodes), and the diodes in series.
    No ill effects should come of this, unless the bias is too hot when the SS rectification is used.

    You would have the choice to set the bias for the higher B+ and run cooler bias when the tube rectifier was switched in, OR you could devise a switch to change the bias resistor whenever a different rectifier is chosen.

    I would probably let it have cooler bias when the B+ was lower, to have a bigger tonal effect when switched between the two rectifier methods.

    EDIT: You only want to switch the rectifiers when the power is *OFF*. If the switch would fail there may be 400 Volts on the switch your fingers would touch.:eek:
     
    Last edited: Mar 3, 2021
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  6. Sam VanLaningham

    Sam VanLaningham Tele-Meister

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    So for accuracy sake, I want to update the above layout images.......the images above are WRONG! Right? Heres how its supposed to be, with the SS rectifier diodes coming off the plates (1 and 7......Im learning!). I realize its hard to dig deep into the nitty gritty of others layouts so I only blame my lack of knowledge....

    upload_2021-3-10_21-37-45.png
     
  7. Sam VanLaningham

    Sam VanLaningham Tele-Meister

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    This whole endeavor came about because:

    1) this amp is getting some serious RFI

    so Ive been mucking about in it, new/better/different grounding schemes etc...resoldering.....adding shielded leads coming off the input jacks.....

    2) now EZ81 is shorting

    And i was being tight not wanting to buy a new ez81 if the problem was downstream.....
    So I tried the SS setup because I have the switch and diodes on hand....with light bulb limiter it showed no probs and it worked for a sec.......but then stopped making sound at all. Booooo!!!

    I thought maybe I had a wrong SS layout, a blown OT, who knows. I tried a few simple tests of OT with MM but didn't see anything suspicious. So new ez81 is coming saturday.

    Any additional thoughts if your reading would be amazing! Sam
     
  8. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    You’re doing a good job thinking about this switch. I gotta admit though I’m not quite clear about your reason for wanting SS rectification. Or switchable rectification. Is it a noise thing?
     
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  9. Sam VanLaningham

    Sam VanLaningham Tele-Meister

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    Hey kingfan thanks for getting in here. Yeah i think my reasoning was/is not robust.....as i was troubleshooting RFI, the ez81 acted up and i have no idea why. So rather than spending $13 on a new ez81 and waiting for its arrival, i thought i have the ability and parts to make a ss rectifier. I figured this would help me determine if its the tube or downstream along the the B+, i guess?

    So the RFI and ez81 were sort of independent troubleshooting issues that came up somewhat simultaneously if that makes sense.
     
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