Marshall SC20H weird problem! I am getting desperate so please help...

Discussion in 'Marshall Amps' started by CroTone, Mar 4, 2021.

  1. CroTone

    CroTone Active Member

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    I had a previous issue with a brand new DSL20HR, also out of the box, but according to my store guy...that one had severe issues and, in the end, it was sent back to Marshall as a verified faulty model.
    In all honesty, I did my research and read through forums that there were some considerable reliability issues with the DSL20HR series, especially early models, however, mine was December 2020 model and still was messed up. Quality control seems to be a real issue here. I understand that many times it is hit & miss (as with anything in life), especially for the price that you pay...but I think that new stuff must work from start and there is no negotiation with that.
    If my studio JCM 800 only had a problem with a single preamp tube, then I can live with that for sure. Let's hope it serves me well for the years to come.
    I replaced all three tubes with new JJ's ECC83 and hopefully that settles it.
    Sounds gorgeous for sure!:wub:
     
    Last edited: Mar 5, 2021
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  2. CroTone

    CroTone Active Member

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    Thanks for the link man! cheers!
     
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  3. Madfinger

    Madfinger Well-Known Member

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    Smart move :agreed:
     
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  4. pedecamp

    pedecamp Well-Known Member

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    Congrats you fixed it! If you like the way the amp sounds then no need to replace any of the other tubes, definitely get a spare 12AX7 to keep around for emergency, any brand that you like.
     
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  5. scozz

    scozz Well-Known Member Gold Supporting Member

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    Isn’t it always the tube closest to the inputs?

    I was under the impression that it is, but I could very well be wrong.
     
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  6. pedecamp

    pedecamp Well-Known Member

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    Keep the old tubes as spares (throw away the bad one). Glad you got it sorted out! :yesway:
     
  7. ampeq

    ampeq Well-Known Member

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    Shipping tube amps is always a nightmare, it’s really best to pull the tubes & bubble wrap them. I’m surprised more don’t break in shipping, it amazed me my Ceriatone amps both made it from Malaysia in one piece.
     
  8. scozz

    scozz Well-Known Member Gold Supporting Member

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    I changed out both the power tubes and preamp tubes in my SC20. I put two Mullard New Production EL34s and 3 tungsol 12AX7s’.

    I think it sounds a bit fuller or thicker with the new tubes, but these are subtle differences when using the same value tubes.

    You could also try different value tubes, like using Kt66 tubes in place of the el34s’,....or say 5751 preamp tubes in place of the 12Ax7s’.

    There are others too that can be used in a SC20. Just make sure you use a tubes that are compatible with your SC20.

    Best of luck going forward, and we’d love to hear your thoughts on it in the SC20 Thread.

    https://www.marshallforum.com/threads/the-official-marshall-studio-classic-thread-sc20.105824/
     
  9. RCM 800

    RCM 800 Well-Known Member

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    OP you should order a pair of El34's as well as a couple 12ax7's to have on hand. Tubes are wear items like picks and strings. Its a good idea to have spares on hand.
     
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  10. Sustainium

    Sustainium Well-Known Member

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    Glad to hear you solved the problem and now get to reap the SC20H rewards!:cheers:
     
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  11. ampeq

    ampeq Well-Known Member

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    This is a must, I always keep a few pre amp tubes as well as a full set of EL34’s and 6L6’s for testing or a emergency.
     
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  12. JamminJeff

    JamminJeff Well-Known Member

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    I can't tell you how to feel, but I can share that tubes/valves will "glow" and not work. Sometimes they won't glow, but will work, sort of. Tube amps are old technology, which is why we love them, but sometime they do wonky things, even new ones.

    EDIT: Went further back and read the new posts. Congrats on finding the fix !
     
    Last edited: Mar 5, 2021
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  13. CroTone

    CroTone Active Member

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    Follow-up:
    Amp works perfectly fine after a couple of on/off test-drives throughout the day.
    Thank you guys for your valuable suggestions and advices!
    You all rock and I wouldn't make it without your help. :hippie::dude:

    Regarding the preamp tubes stuff...
    I additionally ordered a Mullard CV4004 that I plan to insert into the V1 position - it seems that one might be what I am looking for and I also ordered two additional 12AX7 Tung-Sols for other positions. However, will probably keep JJ's in V2 and V3 because I have the most experience with those and they are a decent all-around choice. I will keep stock of others as spares. My next move will be getting a pair of EL34's so I can save them as spares.
     
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  14. CroTone

    CroTone Active Member

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    Great stuff man!
    I will certainly chime in on that topic once I test-drive this baby a bit more... but judging by how the thing sounds at this moment, I think it is going to be a very very positive review!:applause:
     
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  15. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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    If it sounds good, I wouldn't change all the pre tubes out. Try it, record it amd see if it sounds any different from stock. If not, leave it.
     
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  16. Old Punker

    Old Punker Well-Known Member

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    Hi @matttornado - I have the Fryette Power Station 2. This is actually a re-amper. It takes your amplifier's output and re-amplifies it at the volume of your choice through its own 50W all tube power amp. It is useful not only as a very transparent attenuator, but can also be used to make a small (eg. 1W) practice amp sound a lot bigger, and it can provide an excellent FX loop for amps that don't have one. You can also use it as a clean 50W amp to use directly with other preamps, effects, amp simulators, etc. :)
     
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  17. Old Punker

    Old Punker Well-Known Member

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    ^^ +1

    I changed out all of the preamp tubes at the same time in my Mesa once and suddenly had some weird noises start up that took me a long time to track down, again best to not change what is working and only swap one at a time, especially since the tubes in your amp are all new. Preamp tubes can last a really long time, as compared to power tubes. The V1 tube you pulled out may/may not actually be defective, as there is the possibility that it merely became unseated during shipment. If you haven't already tossed it out, you could try it in your other amp to see if it works. Also, I wouldn't worry about your amp being 'problematic' or anything, if you are getting great tone after replacing the one bad tube, you are all set! I've heard that QC is very good at Marshall's UK factory, and they properly test everything before going out the door.

    I love the tone from my SC20H and plan to replace worn tubes with the same type and brand in the future, but I am a stickler for consistency. I think you mentioned using some new Tung Sol's - if you start to get some (low volume) crackles or pops don't panic. Give these TS's at least 25 hours of play time and they will probably become very quiet again (from experience). And only some of the new TS's are noisy at first. The noise you get from the SC Tele is normal, as you know.

    I don't know what sort of cab you are playing through but if you can try at least a 2x12 or a 4x12 if you have one.

    Rock on! :dude:
     
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  18. CroTone

    CroTone Active Member

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    Thanks for a bunch of good points! I can only agree with what you wrote, either I will leave these JJ's in or perhaps return back stock Marshall's in V2 and V3.
    I haven't tossed the "bad" one yet, it is in my drawer somewhere so I might use it someday in another amp to see if it works.
    I just bought some tubes today so I can create some tube stash to use in the future when needed to test something, replace, etc.

    And yes, amp operates perfectly so I guess it would be unjust to call it "problematic" ever again. :D

    Regarding the cab, at this point, I only have an ENGL pro cabinet with Celestion V30 (it is a 1x12 cab). It is one but it sounds phenomenal and it is built like a tank.:jam:
     
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  19. JamminJeff

    JamminJeff Well-Known Member

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    It's easy to loose track of what the factory tubes actually sounded like if the tube rolling thing is not recorded or at least some notes are made. Paper notes, not guitar notes, but you get me drift.

    If you really want to go all tube goober, make a spreadsheet with enough columns to enter all the values, brand, ect. Make notes of the description of what YOU are hearing. Make sure tube warm-up is exactly the same amount of time for each test, including time played. Some amps sound best after an hour of playing so there are many variables to consider.

    I don't go down the tube goober rabbit hole anymore and just play what sounds good. If you find what you like, buy more.....:)

    p.s. Tube/Valves change from lot to lot and sometimes even within the same lot. It's old technology but it still can't be replicated !
     
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  20. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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    I have my Excel spreadsheet for what tubes live where in which amps.
     
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