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Studio B Glowy Toxic Mercury Power Supply MOD

Discussion in 'Modifications and Tweaks' started by purr1n, Oct 29, 2022.

  1. purr1n

    purr1n Desire for betterer is endless.

    Staff Member Pyrate BWC
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    This is a retro-fit to use the type 83 tube per @tommytakis's request. Will provide more information (schematics - what to do) upon further request, discussions, questions. Mercury vapor rectifiers have a blue glow and look cool. They do sound different, being stiffer, less voltage drop, constant voltage despite variations in current draw. This latter really not an issue with SET amps, but it doesn't make an audible difference. I haven't read and compared the specs of the 83 and the 5AR4 (original power tube in Studio B).

    The mercury inside the tube needs to be vaporized before connecting B+. This is why this mod requires the installation of a switch. The switch turns on the filament heater first. What happens next is that mercury slowly vaporizes. Give it a minute or two. Longer if the amp hasn't been turned on in a while. Although from what I understand, the type 83 is OK, that it won't arc, without first doing this. I'd rather be safe though. The type 83 is directly heated unlike the 5AR4. The filaments of the type 83 also require more current than what the existing combo power transformer can provide, hence the need to install an additional power transformer.

    Parts List.

    https://www.tubesandmore.com/products/transformer-hammond-low-voltage-filament-open-5-vct
    Hammond 5V 3A transformer.
    Only need one but must be this size.

    Tube socket:
    https://www.ebay.com/itm/223512247405

    Power switch:
    https://www.cedist.com/products/switch-carling-toggle-spst-replacement-fender

    Turn silver switch on for 1 minute before turning Black power switch on.

    Type 83
    upload_2022-10-29_8-40-0.png

    5AR4
    upload_2022-10-29_8-40-42.png

    @Josh Schor: Can you take photos of your power supply?

    Caveats:
    1. You may die or receive a horrible electric shock if precautions are not taken while performing this mod
    2. You may still die or get very sick even if you do take precautions
    3. You will lose your warranty, unless you send parts to Craig's builder - I have his contact info
    4. Mercury is toxic. If the glass breaks, that's on you. Get your own hazmat suit.
    5. No one should be doing this mod; and SBAF and I do not condone it.
     
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    Last edited: Oct 29, 2022
    purr1n, Oct 29, 2022
    #1
  2. Josh Schor

    Josh Schor Friend

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    I will take internal and external photos next week and post them.
     
    Josh Schor, Oct 29, 2022
    #2
  3. GanGreinke

    GanGreinke Friend

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    Is this a mod that can be done for the Aficionado PS? Are the parts the same?
     
    GanGreinke, Oct 30, 2022
    #3
  4. atomicbob

    atomicbob dScope Yoda

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    A long time ago I had the opportunity to learn about 866A mercury vapor rectifier tubes in a linear amplifier using 4x 811A power triodes to achieve approximately 1 KW for radio use. Pay particularly close attention to @purr1n 's caveats. I will add a few.

    1) unless you are a very advanced, very experienced DIYer with high voltage experience, don't do this.
    2) voltages involved are likely to kill you if you accidentally touch a live HV circuit
    3) mercury vapor looks pretty but you MUST pay attention to power up sequence. Filaments on for at least one full minute for the mercury vapor tube to reach operational temperature before turning on the B+ high voltage. Failure to follow procedure is likely to result in a lot of sparks, noise and possibly catastrophic failure of the power supply.

    Personally, I am so very happy with my EC Studio B that even though I have the knowledge and experience to do this mod, I won't. Not only due to the reasons stated in the caveats but I also don't wish to jeopardize the sound achieved by this very well designed headphone amplifier.
     
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    atomicbob, Oct 30, 2022
    #4
  5. purr1n

    purr1n Desire for betterer is endless.

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    Yes.
     
    purr1n, Oct 30, 2022
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  6. TheloniuSnoop

    TheloniuSnoop Friend

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    TheloniuSnoop, Oct 30, 2022
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  7. Cspirou

    Cspirou They call me Sparky

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    I remember seeing an amp by Frank Cooter that used Hg vapor tubes. I wish I could have heard it
     
    Cspirou, Oct 30, 2022
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  8. tommytakis

    tommytakis MOT: E.T.A Headphones

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    @purr1n If our EC amp uses half-wave rectifiers like EY500A (mkiv, 445, Studio-T/M), I'm guessing we'd need to find a different type of Mercury or Xenon that's also half-wave? Would the BoM list you provided above still be relevant? or will it be a completely different build?
     
    tommytakis, Nov 1, 2022
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  9. Josh Schor

    Josh Schor Friend

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    Heres some photos of the insides of the power supply note on switch was my wifes request when she uses and Im not there
    IMG-0589.jpg IMG-0588.jpg IMG-0587.jpg IMG-0586.jpg IMG-0585.jpg IMG-0583.jpg IMG-0582.jpg IMG-0581.jpg IMG-0579.jpg
     
    Josh Schor, Nov 1, 2022
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  10. purr1n

    purr1n Desire for betterer is endless.

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    You are correct.

    866A should work. Power transformer should be appropriately sized for current draw. (Just confirm via data sheet). At this point better to transport power supply boards into a new chassis. Be aware of transformer and choke placement and orientation if there are several.
     
    purr1n, Nov 1, 2022
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  11. Cspirou

    Cspirou They call me Sparky

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    There's a guy I follow that makes tubed based digital computers and has a vid on mercury rectifiers

     
    Cspirou, Nov 3, 2022
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  12. joch

    joch Friend

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    I'm with AB on this perspective (and the potential dangers), but the glow is just so beautiful.

    @Josh Schor how does Type 83 compared to the 5AR4?

    Other than the cool blue glow, is the change to the EC SB just different, or betterer?
     
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    joch, Nov 3, 2022
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  13. Josh Schor

    Josh Schor Friend

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    I cannot say if its better. I have new speakers which are now broken in the amp sounds fantastic and I do not know.
     
    Josh Schor, Nov 3, 2022
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  14. purr1n

    purr1n Desire for betterer is endless.

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    On the same amp, I tried mercury, xenon, and fast recovery solid-state diodes (yes you can cram diodes into the rectifier tube socket). They all sound different. The solid-state parts sounded the most grainy or solid-state. The xenon gas were the cleanest sounding. The mercury were slightly grungier but had the most balls. The differences were not huge.

    At the epic 2010 Bay Area meet organized by @CEE TEE (not Jude - never Jude), Frank Cooter brought possibly the most epic tube electrostatic amp ever. It used a custom Electra Print output transformer. Don't remember the topology or tubes used, but I do definitely remember the mercury vapor rectifiers.

    Frank Cooter was eventually spooked into NOT bringing such potentially toxic tubes to future meets. The story is some dimwit at that meet almost sat on them. Dimwits are almost always the reason why we don't get nice things.

    His amps at later meets sounded good, but they were never able to make the stats headphones slam.

    I have the schematics to Frank's amp stashed away somewhere. I will post if and when I find them.
     
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    purr1n, Nov 3, 2022
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  15. Tom R

    Tom R Acquaintance

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    When pirate radio was big I built HV power supply for an AM transmitter using a pair of 866A Mercury Vapor rectifiers. 2000V @ 1A. I learned a few things doing it. They don't like capacitance. At all. So I put some RF chokes in each plate lead and used a choke input filter. The filaments have to be preheated for at least a minute before turning in the HV. I used a PB time delay relay. The other thing is they put out a shit ton of broadband EMI. Crazy amounts.
     
    Tom R, Nov 4, 2022
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  16. Kashalott

    Kashalott New

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    I am currently designing my own dht amplifier and I plan to use 394a mercury thyratrons as rectifiers. Having investigated it in various other forums, choke input filter is not a necessity if you implement a slow start circuit, then those beauties can tolerate some small input capacitance.
     
    Kashalott, Nov 4, 2022
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  17. Tom R

    Tom R Acquaintance

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    Enjoy the build, sounds like an awesome project. Do consider some small chokes (100 uH) near the tube caps - really helps with EMI.
     
    Last edited: Nov 6, 2022
    Tom R, Nov 6, 2022
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