Longest Metro Plexi 50 Build

Discussion in 'Building the Classics' started by Exojam, Aug 4, 2018.

  1. Exojam

    Exojam Active Member

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    Well I have decided to start getting this build on the way. Have not made to much progress but I am in no rush at all.

    I am using Marstan PT, OT and choke.

    Picked up all the parts from Valvestrom.

    More pics when I make more progress.


     
  2. ampmadscientist

    ampmadscientist Well-Known Member

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  3. Exojam

    Exojam Active Member

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    Well with being in the process of a 19 month period to stay alive and now recover, trying to fix this Blackstar HT100 Head, practice my guitar and have a family.

    It will be a long build time :eddie::eddie:
     
  4. Exojam

    Exojam Active Member

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    Plus a good 9”’s!
     
  5. Exojam

    Exojam Active Member

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  6. Big Mike

    Big Mike Member

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    Heaters look pretty good, those are annoying.
     
  7. Exojam

    Exojam Active Member

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    Thank you. Yeah, getting my chubby fingers in there to twist them was not the most fun thing.
     
  8. Gunner64

    Gunner64 Well-Known Member

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    Try tying one end of the pair to something stationary and put the other end in a cordless drill and twist away..dont go too far though..no need to twist in the amp..I pre-twist.
     
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  9. Exojam

    Exojam Active Member

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    Gunner,

    I had seen that done before but I was not sure if I could use that method due to one end of the wires being of different length. Plus, I was not sure how much extra I would have but I will pre twist going forward.

    Thanks for the input.
     
  10. neikeel

    neikeel Well-Known Member

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    The drill method works well but you do lose a bit of wire when you untwist enough to solder the ends in.
    Personally I don’t leave those long black loops in the preamp pin 9 wires.
     
  11. ampmadscientist

    ampmadscientist Well-Known Member

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    That is long.
    Perhaps the longest.
     
    Last edited: Aug 31, 2018
  12. Exojam

    Exojam Active Member

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    What is the purpose of those loops if any (as I cannot see any benefit)? I just tried to make it like the instructions showed.
     
  13. Exojam

    Exojam Active Member

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    The 19 months was hardest shit I have ever been through, and being a para for going on 20 years, I have been through some tough goes of it.
     
  14. neikeel

    neikeel Well-Known Member

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    Don’t know really I think idea was to approach the sockets at 90 degrees and ensure the other wires crossed these at 90degrees to.
     
  15. ampmadscientist

    ampmadscientist Well-Known Member

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    If the signal wires are parallel to heater wires, you get a lot of hum.
    If the signal wires are 90 degrees, you will pick up a lot less hum.

    But it actually helps to get the heater wires vertical straight up from the socket too. That's how Fender does the filaments.
    In this case heaters vertical and signal down near the chassis, the noise is reduced more.
     
  16. neikeel

    neikeel Well-Known Member

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    Yes that is what I said. :)
    What I am not sure is why such big loops as I think that they are more likely to encroach on grid wires and cause noise.
     
  17. Exojam

    Exojam Active Member

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    I told you guys it would be a long build.

    I had to put it down for awhile while I try and finish fixing (I hope) this Blackstar HT100 I had purchased that I purchased knowing it did not work. Getting close to wrapping it up and will see if I got it or not. Than back to the Plexi.

    I received the below wiring change (from the book) from the gentleman from Valvestrom.

    Notes:

    AC Line in -

    L (Hot) black wire to tip of mains fuse holder, sleeve of fuseholder to one side of power switch, other side of switch to brown (120) PT wire AND to one side of 120vac lamp

    N (Neutral) white wire to H on PT, H also goes to other side of lamp via a white wire.

    G to new, dedicated ground lug on end of chassis

    The other PT AC wires (1,3,4,5) should have individually heatshrinked tip then be bundled out of the way.


    PT Secondaries – To rectifier as indicated above.

    I use D & F initially, these will yield voltages that are more friendly to modern power tubes, C & G are higher voltage, can easily more the wires if desired.


    Heaters – to v5 as indicated above. J to ground lug
     
  18. Exojam

    Exojam Active Member

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    Well I had to jump ahead of the instruction manual and hooked up the below wiring, baby steps.

    Next is is to drill a hole in the chassis for a ground lug for “G” of the input power.

    AC Line in -

    L (Hot) black wire to tip of mains fuse holder, sleeve of fuseholder to one side of power switch, other side of switch to brown (120) PT wire AND to one side of 120vac lamp

    N (Neutral) white wire to H on PT, H also goes to other side of lamp via a white wire.

    FC37A022-6142-418D-9399-233FAD6D7109.jpeg 483EE839-2AC4-43B0-9E3B-F275FE154FFB.jpeg
     
  19. neikeel

    neikeel Well-Known Member

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    Normally you bring the ac wires in the corner of the chassis and then up from the front to the PT (ie dont have that white neutral wire there, run it under the rectifier in that loom bundle then up to the lug. You will shrtly take another white wire from the HT lug to the bias feed on the board;)
     
  20. Exojam

    Exojam Active Member

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    No problem, that will just take a few minutes to unsolder the connections and run another piece of wire. Thanks.
     

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