Bias Probes

Discussion in 'The Workbench' started by CKCinMass, Dec 11, 2009.

  1. jcmjmp

    jcmjmp Well-Known Member

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    Are those PTs particular to a certain era, years, models (i.e. MKII)?
    My 2204 has a Drake 1202-304/3 PT. Its effing HUGE compared to the PTs on my other Marshalls.
    [​IMG]

    CKCinMass: Which PT do you have in your 2204?
     
    Last edited: Dec 12, 2009
  2. MajorNut1967

    MajorNut1967 New Member

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    Hey Sport there is no Drake PT # 1202-304/3 that Marshall used in a 50 watt!

    There is a 1202-324/3, which is the international 1980's 50 watt power transformer which by the way has a 100v Japan tap, which might explain why you have such high plate voltage of your amp if you live in the US? The Standard PT for your year of 2204 is the 1202-324
     
  3. CKCinMass

    CKCinMass Active Member

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    My '80 2204 has a 1202-324 (Drake I believe) and my '87 2204S has a 1202-324/5 Drake.
     
  4. MajorNut1967

    MajorNut1967 New Member

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    Those Are correct.
     
  5. jcmjmp

    jcmjmp Well-Known Member

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    Sorry to burst you bubble, Major but... this amp is bone stock and has a Drake 1202-304/3 - I just double checked.

    It is a Canadian amp, with metal toggle switches and separate indicator light. The amp came with ITC EL34 power tubes in stock form, which I still have. The other 2204 (Canadian version) was Identical.

    The Canadian Silver Jubilees also had different PT and OTs vs the US versions. Maybe that's why there is a difference. I'm kinda curious about these amps now. I wonder how rare these things are.
     
  6. jcmjmp

    jcmjmp Well-Known Member

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  7. MajorNut1967

    MajorNut1967 New Member

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    Wait are you Canadian? That would explain a lot.
    I have the US/CA JCM 800 service manuals and it states the PT for Canadian models should be: “Drake #1202-324/3” transformer. Again why is it you only have all these odd-ball amps and theories? Did you buy those amps brand new out the box? Maybe the ink on the part # is smeared? Twice! So I take it that you are an expert on Canadian Marshall Amps and what exactly qualifies you as a Canadian Marshall Amps expert? Also why is it you are always post other peoples info or websites to prove yourself? Can't you validate your points on your own? And can you please explain what’s the difference in your special Canadian transformers, opposed to the standard Marshall transformers? I’m sure the others and I would love to gain all the knowledge you have on these matters!
     
  8. jcmjmp

    jcmjmp Well-Known Member

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    I have no clue where you're coming from sometimes.

    1) Why do I link to other's websites to prove myself? Because you didn't believe me when I said that I had a 1202-304/3 PT in a STOCK Marshall JCM800 2204 from 1983.
    2) I never claimed to be an expert on Canadian Marshall Amps
    3) Can I validate points on my own? See 1)
    4) The difference between the Canadian version and the US version of the PTs seems to be in the B+ voltage.... that's what I learned from this thread, but I may be wrong. Maybe some other 2204s have these PTs.
    5) Why do I have all these Odd ball amps and theories? I don't know what you're talking about here, Major. These amps are pretty standard here in Canada.
    6) My amp was bought brand new and I don't seem to be the only one with these PTs (as per the links I provided you).
    7) The ink is not smeared, twice. You have 3 instances of these PTs with crisp and clear identification. One is mine and the other two are from the amp archives pictures.
    8) Yes, I am Canadian. Not sure what that explains to you.

    I have a question for you: Why are you always so aggressive when someone doesn't agree with everything you say 100%?

    I hope I answered all of your questions.
     
  9. MajorNut1967

    MajorNut1967 New Member

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    Actually I really don't care much about this at all! I don't know anything about Canadian Marshall, much less do I care. I mainly did this to show that you have a propensity to always to have to be right and that you will high-jack someone else’s Post with your two cents even though is has nothing to do with their issue or question! And you are always getting caught by the people who know you are full of it. And now I have lowered my self to High-Jack this lad’s post just to prove a point. Son, “you’re a legend in your own mind!”
     
  10. MajorNut1967

    MajorNut1967 New Member

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    CKCinMass,

    I want to apologies to you and the others for high-jacking your post to prove a point. I will have respect to leave the post for the duration. Good luck on your bias probe project and if I can be of any assistance to you on this further just PM me.

    Cheers Mate!
     
  11. jcmjmp

    jcmjmp Well-Known Member

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    WoW! :confused: :lol: Are you ok?

    I don't know what you're talking about... again. Where did I show this propensity to always have to be right? I only stated that the 2204s I have seen (2 of them) had a plate voltage of 470vdc and I was not aware that these amps normally have much lower plate voltage. The only problem here is that it doesn't match what you stated. You seem to have a problem with people that don't share your experience and opinion it seems. You don't care about any of this but you're still drawn in and feel the need to post nothing but aggressive posts because someone has measured a plate voltage of 470vdc instead of the one that you're used to seeing.

    I have nothing to prove, never claimed to be an expert as you say and everything to learn. Its weird how you keep making stuff up. You're doing all of this to show everyone what, exactly?

    I provided info WRT to the bias probe and plate voltage probe yet you still came after me and derailed this thread as you usually do.

    This voltage difference is interesting. I'll have to look into this discrepancy further.
     
  12. NewReligion

    NewReligion Well-Known Member Double Platinum Supporting Member VIP Member

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    Feel the Love!! LOL. :)
     
  13. Iron Mang

    Iron Mang New Member

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    Hmmmmmmm? I notice that you tend to post on almost everything. So you must have vast experience, just how old are you and how many years have you been working in the field? You know one way you could shut up some of the guys is to put up a thread of an Amp you have built from scratch or post a schematic of an amp you designed all on your own? That'll do it!
     
  14. jcmjmp

    jcmjmp Well-Known Member

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    I'm nearing 40 and you're right, I post on a lot of subjects. I have a college electronics degree, do woodworking (built a few guitars), carpentry (built my home), play in two bands (cut down from three), done some recording at home and in pro studios, played live shows in small venues to outdoor festivals. I love guitars and I love playing 'em. I spent all day recording yesterday - I love, breathe this stuff.

    I haven't built amps from scratch but I've modded and fixed a few, tube and solid state. I'm by no means a tube expert and I'm still learning a few things with regards to tube theory (they didn't teach tube theory back in 1987). I have designed solid state audio amplifiers, RF amps, dabbed in digital but I mostly work in software now. I love this stuff. I've got a curious mind and like to constantly learn stuff. Fixing stuff is so rewarding too.

    I have built guitars from scratch but playing guitar is my #1 priority. I only got into building guitars because I couldn't find what I wanted and got into fixing/modding tube amps because I have electronics training and there are no competent techs around here. Not that I know of at least.

    I am by no means as knowledgeable as someone like Wilder WRT tube amps. He's a great asset to this forum. So is PaoloJM.

    Hope this helps.
     
  15. Iron Mang

    Iron Mang New Member

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    Maybe I wasn't clear enough. I was not asking you to help me. I was kind of making a suggestion of how to get the dogs off you. Through your own admission you have said you are not that experienced in Tubes. And while you may have a degree in Electronics, I notice in a post where Mr. Wilder had explained some of the theory of a "shunt switch" and you said to effect that "its not a true bypass" well if you truly had an Electroincs background you should have know that a Shunt switch is a genuine bypass because the current can only flow in one direction!
     
  16. CKCinMass

    CKCinMass Active Member

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    Here are some shots of my '80 2204 80 2204 gut shot.jpg

    80 2204 front.jpg

    80 2204 pt.jpg
     
  17. jcmjmp

    jcmjmp Well-Known Member

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    true bypass in the sense of a 2p2t switch. Wire bypass is different but in that example, its pretty much equivalent, esp. for 60Hz large power signals.

    hope that helps :hippie:
     
  18. jcmjmp

    jcmjmp Well-Known Member

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    nice chassis and amp! too bad about the holes though :(
     
  19. CKCinMass

    CKCinMass Active Member

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    The chassis was factory drilled for 4 holes. The aluminum overlay covered those holes until the butthead who had the amp before me decided to punch them out. I will probably use a couple of chrome caps to cover those up. I'd like to get a new face plate but the one I have has the serial # stamped into it so I'd lose one more bit of originality. This thing will never be a museum piece but if I sell it I want to get decent money for it.
     
  20. luekemeyer

    luekemeyer New Member

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    Testosterone at is best.
     

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