1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

Simplified 5E8a Layout

Discussion in 'Shock Brother's DIY Amps' started by nathanh, Dec 27, 2018.

  1. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    I believe the one in the amp to be in working condition. I just felt like if I'm going to upgrade any part of it then it might as well be that one. Hey, maybe not?

    How does this look for the HRD rec my friends?

    Screen Shot 2018-12-29 at 9.04.06 PM.png Screen Shot 2018-12-29 at 9.22.13 PM.png
     
    peteb likes this.
  2. Nickfl

    Nickfl Friend of Leo's

    Posts:
    2,532
    Joined:
    May 24, 2016
    Location:
    Florida
    I noticed a mistake on the bias supply in your layout, the connection to the 20uf filter cap should be coming from the junction of the diode and the 56K resistor and you have it coming from the junction of the diode and the 3.3K resistor.

    While you are at it, I highly recommend you add an adjustment pot to the bias circuit so that you can dial in the bias on your power tubes without changing out a resistor. Look up the adjustable fixed bias information on Robrob's website for examples.
     
  3. Nickfl

    Nickfl Friend of Leo's

    Posts:
    2,532
    Joined:
    May 24, 2016
    Location:
    Florida
    That looks correct to me, though I am not sure what the purpose of the cap across HT secondary is. I have never seen that done on a bridge rectifier before.

    If you want to simulate the sag and voltage drop of a gz34 rectifier, you would need to put a resistor in series after the output of the rectifier. Probably something like a 100R 10W resistor would do the trick and it should drop your B+ down to around 415 volts, which would put your voltage right in line with the 5e8a schematic.

    As for the OT, don't go buying a new one just because you assume it must be better. I'd do some research first and try to figure out how the HRD transformer compares to what you are looking at as an upgrade. I'd guess any other transformer sold for that amp would be the same primary impedance as the one you have so the only possible difference would be the size and quality of the iron, which is hard to quantify as it relates to the sound of your finished amp. Personally I'd just use the HRD OT, remember that you are already going to have to drop some cash on a new choke unless you want to deviate from the 5e8a power supply design so that you can use the HRD choke.
     
    nathanh likes this.
  4. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    @Nickfl I've never seen it either honestly.

    While I had seen a bridge rec layout before it actually took me a lot longer to draw one from a schematic than I care to admit. I had the hardest time for no reason.

    I should have a revised layout up soonish. Thanks for the help and advice.
     
  5. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    Actually im trying to get a grip on the HRD schematic and then decide how I'd want to go forward. The highlighted section is new to me though. Can anyone point me in the right direction? Everything else makes sense and I see the actual bias section before it.

    Screen Shot 2018-12-30 at 8.53.30 AM.png
     
  6. Tom Kamphuys

    Tom Kamphuys Tele-Holic

    Age:
    41
    Posts:
    716
    Joined:
    Sep 18, 2018
    Location:
    The Netherlands
    The 16V is for the various opamps and transistors/mosfets. I can't find the use of 48V...
     
  7. Nickfl

    Nickfl Friend of Leo's

    Posts:
    2,532
    Joined:
    May 24, 2016
    Location:
    Florida
    That is the power supply for the various solid state components: the reverb, the "more drive", and the relays for the footswitch functions. Nothing you would need in a tweed twin clone.
     
    robrob and Wally like this.
  8. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
  9. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    Im actually having a little trouble drawing out the HRD bias circuit. I've built the one on @robrob 's site before with my Bassman build but this schematic seems quite different. Anybody care to take a crack at it?
     
  10. Snfoilhat

    Snfoilhat Tele-Afflicted

    Age:
    40
    Posts:
    1,396
    Joined:
    Apr 8, 2016
    Location:
    Oakland, CA
    You posted all the voltage supply circuitry for the HRD on the brown secondary winding (post #45). It looks to me like you could just erase everything in the +48/-48 and +16/-16V region, because it's all in parallel with what you want. The HRD bias supply is all intact, the stuff that's left. It ends with the C- designation and -58V. Though I suppose that if you just eliminate all the other parts from that secondary, the voltage will go even lower (more negative) because the brown secondary will have fewer parts drawing current through it. I would guess your whole effort will be influenced by trying to get down to lower voltages throughout the amp.

    The 5E8a used 19 watt 6L6Gs and the HRD uses 30 watt 6L6GCs, right? So the HRD's high voltage secondary is going to be seeing like half of it's usual current demand, and then the B+ voltages may rise even higher. Or were you going to use 6L6GCs from he start? -- i may have missed that.
     
    Nickfl likes this.
  11. peteb

    peteb Friend of Leo's

    Posts:
    4,208
    Joined:
    Apr 25, 2003
    Location:
    Cascadia




    Where did this schematic come from? It looks likes you have duplicated it, but don’t your even numbered diodes need to connect to some where? Ground?



    I will look at that part of the HRD schematic. I like the HRD. It was my first tube amp and I always enjoy comparing it to the vintage amps.
     
    Snfoilhat likes this.
  12. peteb

    peteb Friend of Leo's

    Posts:
    4,208
    Joined:
    Apr 25, 2003
    Location:
    Cascadia
    I see, they are both from the HRD.
     
  13. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    Correct. I just numbered them for my own organization. I went from top to bottom 1-4.

    I had a blues deluxe for years and loved it. Though not tweed at all it sparked my interest in the tweed era.
     
  14. peteb

    peteb Friend of Leo's

    Posts:
    4,208
    Joined:
    Apr 25, 2003
    Location:
    Cascadia



    That’s not an important part, it has nothing to do with the tweed twin.


    Those regulated voltages, +/- 16 for example, are used to run those 4560 transistors (triangle) I n the drive section.
     
    nathanh likes this.
  15. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    Currently I'm trying to wrap my head around this as it's a little different from the 5F6a one. I've never used a transformer with the two brown wires but if Im correct in my thinking, do I just ground one of them and the other is treated like a standard bias wire like in my PT for the 5F6a?
     
    peteb likes this.
  16. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    forgot to upload Screen Shot 2018-12-30 at 12.27.04 PM.png
     
  17. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    8,303
    Joined:
    Dec 29, 2012
    Location:
    United States
    This is my favorite bias circuit and it will work for you. Connect the other wire from the bias tap to the tag strip's center ground terminal:
    [​IMG]
     
    D'tar, Nickfl and peteb like this.
  18. peteb

    peteb Friend of Leo's

    Posts:
    4,208
    Joined:
    Apr 25, 2003
    Location:
    Cascadia

    I think so


    Rob has provided adjustment and balance. A nice way to go.
     
  19. Wally

    Wally Telefied Ad Free Member

    Posts:
    38,714
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    That is going to be one high voltage version of a 5E8A....and the sonics will change due to that high B+ voltage, ime.
     
  20. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    Yeah getting that voltage down is my next task!

    Ok, using robs balance and bias setup and also the solid state rec we discussed earlier here's a the layout.

    Note: no standby switch yet

    5E8a V6.png
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.