rectfier tube to diodes

Discussion in 'Shock Brother's DIY Amps' started by Mongo Park, Nov 10, 2019.

  1. Mongo Park

    Mongo Park Tele-Holic

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    I have noticed some amp builds using Diodes instead of a rectifier tube like a 5Y3. What I am not finding is the specs on the diodes. I read people saying use a uf4007 diode, but are there different values. Do they come rated for volts and watts. So say I want to build a champ what uf4007 diode would I use, or does any garden variety do the job.
    Any help or direction would be appreciated.
    Cheers Ron.
     
  2. Snfoilhat

    Snfoilhat Tele-Afflicted

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  3. corliss1

    corliss1 Friend of Leo's

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    Diodes have a current rating and voltage rating. They don't get a wattage rating since they aren't usually used in a position to do that type of work.

    I always use the 1n4007 but the UF is like fine. "ultra fast." In a rectifier position, and in anything guitar related, I don't think you'd notice a difference.
     
  4. Mongo Park

    Mongo Park Tele-Holic

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    Beauty, thanks for the quick and knowledgeable reply
    Cheers Ron
     
  5. Dacious

    Dacious Poster Extraordinaire

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    Also you"ll note some schematics showed stacked where there's several diodes in parallel, or there's 2,3,4 diodes end to end.

    This is because when you click a power switch and hit them with high AC voltage off the HT secondary it can flash them for an instant past their rating.

    Both stacked and ganged help individual diodes not instantaneously carry overcurrent, or where there's big current draw spread it.

    Diodes let you have one less circuit to worry about, but if you replace a tube rectifier with diodes be warned it will push up voltage some - typically 20-30 volts depending on what's either side. That will raise voltage throughout the preamp and power amp. Not usually a problem unless you're already pushing say EL84s or 6V6s pretty hard.
     
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  6. muscmp

    muscmp Tele-Afflicted

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    some people add the diodes to the rectifier tube so that if the tube goes bad the diodes still work.. that's one of robrob's mods.

    play music!
     
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  7. DavidP

    DavidP Friend of Leo's

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    AKA the "Dynaco mod"!
     
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  8. Wyatt

    Wyatt Tele-Afflicted

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    That’s not quite what they are for.

    The SS diodes are in series with the rectifier. In most cases a rectifier tube will fail and leave the circuit open and the SS diodes will not continue to operate.

    The SS diodes are there for the rare cases where the rectifier shorts “closed.” In those cases the diodes will protect the filter caps from seeing damaging high-tension AC voltage. The tube should be replaced ASAP because the higher voltages can damage other parts

    I specify “solid-state diodes” because a tube rectifier is a diode as well.
     
    Last edited: Nov 11, 2019
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  9. Mongo Park

    Mongo Park Tele-Holic

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    Thanks for the added advice. I was starting from scratch so I will account for the higher Voltage.
     
  10. Peegoo

    Peegoo Tele-Meister

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    Why not install a tube socket, and then use a Weber Copper Cap SS rectifier? You'll always have the option of popping in a glass tube if the notion hits ya.
     
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  11. Dacious

    Dacious Poster Extraordinaire

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    And it still has the advantage of retaining the heater, but not actually using it and reducing stress on the P/T. Should you ever wish to go back to a tube you can.
     
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  12. Viejo

    Viejo Tele-Afflicted

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    Last edited: Nov 12, 2019
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