1970 100watt Tremolo Mess...

Discussion in 'Let's Talk Vintage' started by pleximaster, Nov 25, 2017.

  1. pleximaster

    pleximaster Well-Known Member

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    7064091D-AB29-4CDA-874D-E4CC204367A9.jpeg here is a 1959T model thatneeds ❤️Some love... where to start...?

    Probably an inventory of parts and check up on transformers...

    Then part inventory in my parts stash to find a match

    And tubes... for testing... I only have old unused glass at home right now...

    Let’s see how this progress

    Going to the city with oldest daughter today to look at some potent Christmas gifts...

    Plexi
     
  2. neikeel

    neikeel Well-Known Member

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    Looks like a Scandinavian model that has had a transformer replacement and some caps replaced? The selectors flapping and floating wires make it look worse.
    Yes I would do a static test of all of the passives, clean the pots and jacks, make sure fuses are of correct value and depending on the filter caps (original or replaced) do a reform in situ or a recap (bias caps look original 47 year old ones?). Drop in some 'testing' tubes etc and see how she goes.
     
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  3. Trapland

    Trapland Well-Known Member

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    It looks easily within your ability. Not saying it looks easy, but easier for you than me.


    I definately will follow this one. Thanks,for the ‘before’ photo.
     
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  4. pleximaster

    pleximaster Well-Known Member

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    0D8EE346-335E-443E-AC86-59369D957BA6.jpeg A6057514-911B-4A37-AA83-0CB58965C5E2.jpeg The diode bridge seems to have burned up at some point and is replaced with a homemade one. Should I replace it
    I got these box bridge rectifier but I don’t know how to read the specs from these. Anyone knows?

    Best plexi
     
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  5. TAZIN

    TAZIN Active Member

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    5SB100 is a 5amp/1000V.
    3SB100 is a 3amp/1000V.
     
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  6. pleximaster

    pleximaster Well-Known Member

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    Thanks Tazin!

    plexi
     
  7. neikeel

    neikeel Well-Known Member

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    If if I read the date codes correctly the 5A is correct for the age of the amp!
    I have seen some with a small turret board for the diodes and the blocks around 69 ( maybe Tazin can tell us when?)
     
  8. pleximaster

    pleximaster Well-Known Member

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    Neil Do you think this diodes on the small board are original? There are 8 diods total I have never seen that before only 4 on slightly bigger boards. By 1970 the block bridge rectifiers were more common AFAIK

    best regards plexi
     
  9. pleximaster

    pleximaster Well-Known Member

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    Tazin
    I just noticed that the small block bridge rectifier I got reads 3SB60 not 3SB100 would that make it 3 Amp 600 volts?

    I got a 50 watt Marhall with a block rectifier stamped 1 V R GB256/PA 69 13
    What does that mean?

    Best plexi
     
    Last edited: Nov 28, 2017
  10. danfrank

    danfrank Well-Known Member

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    Hi Pleximaster!

    3SB60 is 3 amps 600 volts.
     

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  11. neikeel

    neikeel Well-Known Member

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    No definitely not like that.
    They are a small piece of perforated paxolin, just the same type as the main boards with the standard turrets. They are wired just like you see the 68 era amps with crossed diodes in the middle. Can't remember where I have a pic of one. I fixed a very late plexi SB just like that a couple of years ago.
     
  12. TAZIN

    TAZIN Active Member

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    The 3SB60 is a 3amp/600V bridge just like danfrank mentioned. There should be additional writing on that 50 watt block rectifier that states its rating.
    The transition from individual diodes on a small perforated board to the block type IR bridge rectifier started in early 1969 and really takes a foot hold with the introduction of the standup mains transformer.
     
  13. danfrank

    danfrank Well-Known Member

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    If find it interesting that Marshall used such overrated bridge rectifiers in these amps. Maybe because they had many failures with the earlier individual diodes? Does anyone know? They went with 1N4007s later on, in the 50 watt models... correct?
     
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  14. TAZIN

    TAZIN Active Member

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    The switch to the block type rectifier probably had to due with failures and to simplify assembly.
     
  15. ampmadscientist

    ampmadscientist Well-Known Member

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    In earlier days, Marshalls blew fuses quite a bit...due to wrong speaker impedance or newer output tubes which draw more current.
    (until the screen grid resistors were added)
    It was better to blow that fuse, than the diodes.
     
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  16. pleximaster

    pleximaster Well-Known Member

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    11258A2D-BE8F-4982-990C-879DE790230C.jpeg 45BBB508-F78B-4D05-A1D4-C3608759D1D1.jpeg 216B0D61-8949-4C17-B750-8107A4AB4D47.jpeg Fixing the leads on the output transformer (they were cut and had shrinking tubing on a them)

    Before and after pics...
     
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  17. pleximaster

    pleximaster Well-Known Member

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    0E60BF48-A1FB-46DC-B1B1-EC32BE4D44B1.jpeg


    I started to tidy up some of the wiring. The mains transformer was for some reason turned the wrong way and all wires were extended... I turned it back again... see if it works this way later...
     
  18. pleximaster

    pleximaster Well-Known Member

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    0FB823A5-69D4-4E75-A694-CA7BD7982CE1.jpeg After I had fixed with the transformers and wiring and doubled checked it I tried to fire up the amp but no sound what so ever...
     
  19. pleximaster

    pleximaster Well-Known Member

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    0D683D72-9535-4C31-9E5F-C387737DE638.jpeg After about 20 minutes... I found out why I didn’t get ant sound....

    Forgot to put in the tubes... :)

    Time for a break! Right?!
     
  20. pleximaster

    pleximaster Well-Known Member

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    I put in tubes and there was sound but I´ll need to rebuild the bias circuitry but not today... :)

    plexi
     
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