Looking for Schematic for Marshall Origin 50

Discussion in 'The Workbench' started by NewReligion, Aug 22, 2019.

  1. NewReligion

    NewReligion Well-Known Member VIP Member

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    Hello gentlemen.

    Can any of you assist me in locating a schematic for the 50 watt Marshall Origin?

    Thank you.

    Respectfully, David Hopkins
     
  2. Micky

    Micky Well-Known Member VIP Member

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    Won't happen for a few years yet...
     
  3. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    [​IMG]
    Just joking, I am laughing.


    Yes there is none to be found on internet.
     
  4. NewReligion

    NewReligion Well-Known Member VIP Member

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    Well it will when I’m finished. Actually I don’t need a schematic I’ll rip it apart and figure it out.

    See if I can turn it into something from my heart that doesn’t need a pedal for under $1000 for the guys that dig high gain.

    David
     
  5. MarshallDog

    MarshallDog Well-Known Member Premium Member

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    If someone wants high gain, why wouldn’t they just buy a higher gain Marshall seeing as they have many options:scratch:
     
  6. NewReligion

    NewReligion Well-Known Member VIP Member

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    Simple as you may have missed my point. $

    Yes affordable quality all analog tube high gain as an option to Friedman, Cameron, Gower, Fortin etc...

    You would be shocked at how many requests I get for my work based on a donor amp at a lessor used price point than the range of a JMP/JCM 800 2987/1959//2203/2204.

    Just trying to help out those who gave less to spend $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

    David
     
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  7. MarshallDog

    MarshallDog Well-Known Member Premium Member

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    Oh I see was thinking the new JCM 800 and Jubilee as options but you are talking even higher gain at non boutique prices!
     
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  8. NewReligion

    NewReligion Well-Known Member VIP Member

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    Exactly.

    I had a friend of mine that wrote for Guitar Player Magazine for more than 25 years who is friends with Malmsteen and you can imagine the endless others.

    He asked me to take his Friedman pink taco 20 W and turn it into a monster so I did my best I will try to post that here.

    My intention is to try to bring that down to the price point of a used Origin 50 at $450-$500 with of $350 or $400 mod and help out those I can.

    David

     
  9. Jason Fieldhouseespk

    Jason Fieldhouseespk Well-Known Member

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    Evening all, been working on a couple of little mods, I intend to pop a PPIMV mod on this, and a little switch for the fx loop on and off...

    Here's where I am with it, if anyone knows of anything that may help me please let me know.

    - The current MV is PRE Phase Inverter, meaning to drive the Phase Inverter you must turn it quite a way up, to 7 or 8...

    - I've located the Plate Resistors (in the picture I mention Cathode, I meant Cathode Follower, is this correct?) And Capacitors, though I can't see where the top 100k resistor connects to the cap, may find out when we flip the board over next week.

    - I think we've located the Grid resistors for the power tubes, though they are definitely not 220k, they appear to be either 56 ohm or 560 ohm. Which I thought odd? Anybody able to chime in there?

    - then there's the footswitch for the fx loop, when it is disconnected the loop defaults to off, which is a pain, so I want a switch on the back to switch it on and off...

    - Everything marked with an X is sounder point also where work is to be done.

    https://www.instagram.com/p/B1zI_2lB0RP/?igshid=1ubv2wf2zc3h9
     
    Last edited: Aug 31, 2019
  10. NewReligion

    NewReligion Well-Known Member VIP Member

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    “I think we've located the Grid resistors for the power tubes, though they are definitely not 220k, they appear to be either 56 ohm or 560 ohm. Which I thought odd? Anybody able to chime in there?

    I believe you have more to study & understand IMO.

    Not being a smart ass but...an EL34 has 3 types of grid components.

    I assume you are speaking about Pin 5 the EL34 CONTROL GRID which when used are (5.6k) not 56k or 560k.

    The resmsinimg grids are Siprerror Grid & Control Grig.

    I suggest looking at a “EL34” pin out diagram.

    Once you better understand we may speak in depth.

    Respectfully, David
     
    Last edited: Aug 31, 2019
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  11. NewReligion

    NewReligion Well-Known Member VIP Member

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    I caution that I do not know “THIS” circuit but bias feed resistors for Marshall EL34 are normally 220k BUT PIN5 Grid Control Resistors when used are often 5.6k

    I again caution...trace carefully. Reverse Engineer CAREFULLY!

    David a.k.a. New Religion
     
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  12. Jason Fieldhouseespk

    Jason Fieldhouseespk Well-Known Member

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    Cool, thank you, just what I was looking for, I looked up the EL34 pin out diagrams to locate that what that was, and looked up the resistor bands to find out what value it is, though we was going to measure it when we open it up any way....
    It just looked like on most schematics the resistor to pin 5 seemed to be 220k....

    This is all pretty much just me researching, and trying to learn, but that's why Ive taken it in to my local tech guy to do the work, who's been working on valve amps since he was 13, well he's 80 now, he's serviced the local area and worked all over the country in his years, so he'll know what this all is when he opens it up, I'm just trying get my head around it. :)

    It is fun for me looking all this up though....
     
  13. Jason Fieldhouseespk

    Jason Fieldhouseespk Well-Known Member

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    You wouldn't be able to have a look at the board and locate those 220k resistors could you? I see 2 of them but not really where I would have expected them, so don't know what they're doing?

    On the 50w head the bias point is off of pin 7.....

    The diagram I used came from here...

    https://www.premierguitar.com/artic...power-tubes-and-their-signature-sounds?page=6
     
  14. Jason Fieldhouseespk

    Jason Fieldhouseespk Well-Known Member

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    You wouldn't be able to have a look at the board and locate those 220k resistors could you? I see 2 of them but not really where I would have expected them to see them...

    I used this diagram for the EL34 pinnouts...

    https://www.premierguitar.com/artic...power-tubes-and-their-signature-sounds?page=6
     
  15. Jason Fieldhouseespk

    Jason Fieldhouseespk Well-Known Member

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    https://images.app.goo.gl/mXAz3dG5PK9dZXdn8

    Right k, found this On a where I can now see the 5.6k resistors in the circuit.... so, the 220k ones are before that then... the one next to the PI then is 220k, and there's one nestled in all the resistors to right of them... are we any warmer... I'll show Robert all this soon as I'm down in town next yo the shop and have to call in soon...
     
  16. pedecamp

    pedecamp Well-Known Member

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    I bet those EHX MIG50's would be a good donor amp for your mods, I see them for a few hundred bucks used.
     
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  17. Jason Fieldhouseespk

    Jason Fieldhouseespk Well-Known Member

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    OMG..... I'm an idiot.... they're sitting under my nose the whole time... look up the schematics for converting a Marshall 50w to a 20w amp, what's the big change in the power section (aside from the 18w transformer of course), the 220k resistors are replaced wiiitthh 100k... nestled inbetween the 2 EL34s are 2 guess what's.... so, ok, there they are I think. Would anyone be able to say if they would agree with this assessment?

    Also, I think I still have to find the right caps, as I think the capacitor the 100k resistors from the PI plates are connected to is the 47pf one, not the .022n ones.... or they may be .22n or .1uf.... every circuit is different, but I'm tracing it bit by bit...

    The boss will know more, he'll probably laugh at my little diagrams, XD
     
  18. Jason Fieldhouseespk

    Jason Fieldhouseespk Well-Known Member

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    Yet more delays I'm afraid, it got very busy for my engineering friend, schools and pubs and clubs wanted equipment installing, and kow he has a 2 week holiday booked and hasn't been able to get to mine, but will have a look when he's back.

    I'm very confident in the mods that I want now, easy enough to do, and I think I can draw up a rough schematic eventually once I get the amp from the shop and turn the board over... just can't get to it, sorry all please be patient :)
     
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  19. RickyLee

    RickyLee Well-Known Member VIP Member

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    That would be me these days. Trying to obtain high quality, high saturation on a very cheap budget.

    Wishing I would have bought one of those nicer and expensive Bogners, Friedmans or even a few Mesas, back when I could afford it before the Gal got laid off . . . .
     
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  20. South Park

    South Park Active Member

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    Keep us posted
     
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