Planning my 5F2A Princeton w solid state rectifer bridge

Discussion in 'Shock Brother's DIY Amps' started by quyda, Nov 30, 2019.

  1. quyda

    quyda TDPRI Member

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    Hi,

    I'm a complete newbie and am planning my 5F2A Princeton, with solid state Rectifer bridge and custom build transformers, I have a few questions
    1a. What rectifier style should I use, Half wave, Full wave? Each style will raise B+ differntly right? How to calculate voltage raise for each style?
    1b. Will diode 600V3A suffice?
    2. What PT high voltage/current should I select? What current? do I need Center tap?
    3. Going SS Rectifier also means that I can eliminate 5V filament, (just order high voltage + 6.3V) right?
    4. Since its custom build I can choose 6.3V filament or 6.3V CT (3.15-0-315), What current? which should I choose and why does Filament Center Tap help eliminate hum?
    5. Since I can order choke pretty cheaply as well, should I order & install one?
    6. Output tranny is 5K & 5W right?

    Thank you,
    Quy
    tube solid state rectifiers.gif
     
  2. Paul-T

    Paul-T Tele-Meister

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    The drawings do show the arrangement you need. You would only use a bridge rectifier if you have a single secondary, as on the top right. Half wave, top left, is pointless. If you have dual secondaries (centre tap), it's the bottom left arrangement. Full wave might save you money, if you find a cheaper single secondary transformer, otherwise there's no functional difference.

    Voltage drop on the typical IN4007 is only, iirc, 0.3v. I used 275-0-275 for my Princeton, I suspect 330 will be very high without a voltage drop from the rectifier and you will need to look for something lower. It should be a simple 1.4 multiplcation to get the B+ I think but others more experienced will chip in. 2A would be typical capacity for the heater.

    tl;dr Select the B+ you want, it affects the sound, some like to go higher, some lower, then it's fairly simple from there.

    If you want to change things up and save $$$ you could look at a toroidal with a single secondary (no centre tap) and full wave bridge rectifier. I'm planning this for a Micro Deluxe build, they're around half the cost. Why are you going custom by the way? Lots of ways will work!
     
    Last edited: Nov 30, 2019
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  3. jimgchord

    jimgchord Tele-Afflicted

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    Output tranny is a bit larger than 5w and the secondary is more in the 7-8k range.
     
  4. quyda

    quyda TDPRI Member

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    6V6 Spec says:
    Plate Vol 250v -> Load Resistance is 5K, 4.5W
    Plate Vol 315v -> Load Resistance is 8.5K, 5.5W
    Now I dont mind running at 4.5W, but what are the benefit of running higher B+? (apart from higher output wattage?)
     
    Last edited: Nov 30, 2019
  5. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Personal experience, B+ I'm the 340v range of the schematic is where it sounds best to me. I get that with a 275v winding and 5y3. Gz34 in the same setup was 370-380v range. SS rectifier will be pretty high for anything more than 275v on the PT.

    Sent from my moto g(6) using Tapatalk
     
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  6. quyda

    quyda TDPRI Member

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    Does running higher B+ than spec have any effect on tube life?
     
  7. Paul-T

    Paul-T Tele-Meister

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    Isn't it around a 10V drop on a GZ34? And will be less than 1v on a diode bridge.
    That suggest to me that with a diode rectifier, a 275 secondary will give 275 x 1.414 = 388V
    A 250V secondary would give circa 350V.
     
    Last edited: Nov 30, 2019
  8. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Also, if you're using a SS rectifier, it will be a lot cleaner amp than typically associated with a 5f2. Definitely won't be the Layla tone that everyone attributes to a Champ. I built one for a guy and he wanted it as clean as possible. With the 275v tap, a gz34, and a 12ay7 it is as clean as it can get and he uses it with a pedal board. Works great, but it doesn't really sound like a Tweed Princeton. So, keep that in mind if going the SS route.

    Sent from my moto g(6) using Tapatalk
     
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  9. quyda

    quyda TDPRI Member

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    So something like this one should work right,
    1. is 60mA (@250V) enough current?
    2. Should I call for 6.4V "no load" voltage?
    I also believe R-Core tranny has the least flux leakage, so no need to to have iron cover?
    O1CN01SBcvab1ESLBtI4PpB_!!1878780350[1].jpg
     
  10. jsnwhite619

    jsnwhite619 Friend of Leo's

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  11. quyda

    quyda TDPRI Member

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    Should I call for 6.4-6.5V "no load" voltage?
     
  12. King Fan

    King Fan Friend of Leo's

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    Heh, you don't sound like a newbie in terms of knowledge -- all your choices appear specialized and specific. In case it can help our smart friends above, what are your goals, and what factors are leading you 'off-road' on the well-traveled and popular route to a 5F2a?
     
    Last edited: Dec 3, 2019 at 11:03 AM
  13. Snfoilhat

    Snfoilhat Tele-Afflicted

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    Resource for estimating voltages by rectifier type:
    Hammond_Rectifier_Guide.png
     
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  14. quyda

    quyda TDPRI Member

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    I'm an IT guy with just some knowledge of electronics though I've build amps (from kit) before, tube amps is an area I have never ventured in before, its not enough to build the whole thing on my own. I research as I go and you guys taught me alot (or pointed me to the right direction).
    The reason for going "off-road" is because it's not easy and cheap for me to ship transformer to where I live, while its cheaper to buy made-to-order tranny from China. Also ditching the Rectifier tube save money and complexity.
    Bottom line, I just want to challenge myself building a cheap but functional guitar tube amp
     
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  15. King Fan

    King Fan Friend of Leo's

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    Cool, that makes sense. If it's all about challenge and fun and saving money, go for it.

    If it was me, I might look at a Chinese PT and OT and 5Y3 that would produce the original circuit and 5f2a sonics. But I also like your 'fresh start' approach.
     
  16. quyda

    quyda TDPRI Member

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    As an engineer, I tend to trust the science side, and from what I learnt, tube rectifiers dont "sag" in a SE amp. SS eliminates 5V coils, tube, socket... and it seems to be a clear win to me lol
     
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