Origin 50 re-tubing

Discussion in 'The Workbench' started by BatmansMarshall, Feb 8, 2021.

  1. BatmansMarshall

    BatmansMarshall Well-Known Member

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    So I am going to switch out the pre-amp tubes. I did this before with a DSL and enjoyed using JJs and Tung Sol instead. I never changed the Power Tubes though for the DSL.

    I am going to replace the stock pre-amp tubes with 2 x TAD 12AX7/JJ ECC83s and 1 x Tung Sol 12AX7. I am thinking of using the TAD/JJs for V1 and V2 and the Tung Sol for phase inverter in V3.

    After that, I will consider if I want to replace the power tubes or not. I have done this before on other amps that needed to be biased again and have dug out schematics and done this myself with a voltameter and turning the bias pot. I am extra careful. I suspect however that with the Origin 50 the stock power tubes should be okay. If not I am thinking of getting a matched set of TAD/JJ EL34 and then bias manually. A bit more expensive to do so I will hold back unless I really think I need to do this. If I do that how many mV across test point CN32?

    [​IMG]

    Test point appears under the yellow wire and Trim 1 pot is the black round pot on the top left portion of that picture.

    Any advice or special tips, welcome.
     
    Last edited by a moderator: Feb 8, 2021
  2. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    how did you come up w/ that formula?

    Just a note, in Marshall amp's, Tung-Sol tubes do not handle cathode follower or PI positions well...
     
  3. BatmansMarshall

    BatmansMarshall Well-Known Member

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    Watching YouTube videos of Origin different tube tests. I saw one test using all JJs. I have two here and one Tung Sol also.

    So you think leave V3 as is or get another JJ?
     
  4. IOSEPHVS

    IOSEPHVS Well-Known Member

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    66 mV
     
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  5. BatmansMarshall

    BatmansMarshall Well-Known Member

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    Well I went and did JJ in 1, JJ in 2 and Tung Sol in 3.

    I'll report back if it goes wrong, but the high end is reduced and feels tighter as well as a little more crunch with some gain.
     
  6. IOSEPHVS

    IOSEPHVS Well-Known Member

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    I went with a matched set of balanced CP Mullard CV4004s, and a matched pair of their EL34s.
     
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  7. MarshallDog

    MarshallDog Well-Known Member Gold Supporting Member

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    There is no standard MV or mA setting. These values are based of the plate voltage and all amps vary a bit and then there is variances in wall/line voltage. You need to measure plate voltage and then that is used in the formula P=(I*0.7)V to get to 70% of max power dissipation for EL34s.

    Not sure about the stock tubes in your 50 but mine came will JJ pres and power tubes which immediately got replaced because I am no fan of JJ's.
     
  8. BatmansMarshall

    BatmansMarshall Well-Known Member

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    Ah right that formula. Okay. I will try that sometime later if I get a bias tester kit. For now I will go with what Marshall recommended if I change the EL84s.

    Mine came with stock Marshall branded tubes. I'll put them aside and if I sell the amp then put them back in like I did the DSL but I am digging the Origin as a pedal platform very much.
     
  9. MarshallDog

    MarshallDog Well-Known Member Gold Supporting Member

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    Those Marshall branded might be JJs??
     
  10. IOSEPHVS

    IOSEPHVS Well-Known Member

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    ORI50Hs leave the factory set at 66 mV across CN32, in full power mode, with all potentiometers set to minimum, and the boost and FX loop off. I have measured three right out of the box, and others on this board have confirmed the same setting. I doubt the technicians measure other voltages and calculate a "secret formula" for each amp during calibration. Frequently, the service manual tells you the exact voltage (JCM6XX = -42 V, JCM900 41XX/45XX = -40 V to -42 V) because the math was already performed when the amp was designed. Of course, if the amp has been modified, or the number is not known, you should probably calculate the bias voltage setting.
     
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  11. MarshallDog

    MarshallDog Well-Known Member Gold Supporting Member

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    Yeah, that might get you in the ball park and its probably biased on the cooler side so they (Marshall) does not have warranty issues with tubes, hopefully its not past 70% which will shorten the tube life.
     
  12. BatmansMarshall

    BatmansMarshall Well-Known Member

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    They could be JJ graded but Chinese stock.
     
  13. IOSEPHVS

    IOSEPHVS Well-Known Member

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    So, the JJ EL34s in the ORI50H, are they the EL34, the EL34L, or the EL34 II NEW? I want to sell mine, along with the ECC83s. Anyone know which ECC83 they are: ECC83S or ECC83MG? I guess they could even be proprietary tubes sold only to Marshall.
     
  14. BatmansMarshall

    BatmansMarshall Well-Known Member

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    Stock Marshall Tube Codes

    The preamps tubes seem to be two VLVE-00049 12AX7B/ECC83 Shuguang High Microphony Gold Logo.

    One VLVE-00066 ECC83S JJ Low Microphony Red Logo.

    I replaced V1 and V2 with TAD JJs. I put a Tung-Sol into V3 but now I think I might try a TAD JJ ECC83. So that will be 3 x JJs in V1-3.

    I have also decided I am going to try and replace the power tubes.

    The PTs are VLVE-00105. That isn't on the list. I linked. However if you look at the pictures online for this tube you will see the JJ logo at their base on the side. So it seems these are JJ-rated. I am thinking of replacing these with a matched pair of TAD EL34L-CZ or just some TAD JJ EL34s. I am leaning towards the CZs.
     
  15. IOSEPHVS

    IOSEPHVS Well-Known Member

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    Yes. I know the VLVE codes. JJ makes two different ECC83s, and three different EL34s.
    I've replaced mine with Mullard CV4004s and EL34s.
     

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