10 series Plexi 50w tremelo head

Discussion in 'Let's Talk Vintage' started by AndyD, Feb 17, 2021.

  1. AndyD

    AndyD Well-Known Member

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    A very good friend of mine has kindly allowed me to post some photos of his amp for the interest of those who might be interested. It looks pretty original to me so I will be interested in any expert opinions.
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  2. kuli

    kuli Active Member

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    Nice amp!
    I am not an expert, but I think those 'flying' rectifier diodes looks scary and dangerous!
    One replaced output valve socket - or is it just the light that makes them look different?
    Was maybe build to fit into a combo too?
    'Dublier' caps (I think their name is), just like in my model 1987 from 1969.
     
  3. neikeel

    neikeel Well-Known Member

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    Looks very original to me - I suspect those diodes are in too!
    Very nice. Does he fire it up regularly to keep everything working properly?
    Oh and I while Kuli is here talking Trems do you still have the 68 Supertrem?
     
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  4. AndyD

    AndyD Well-Known Member

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    Thank you, Neil. It does seem to be a good untouched sort of amp. The big filter caps scare me. He does fire it up occasionally but probably not often enough. How often should it be switched on to maintain the caps?
     
  5. 11068

    11068 New Member

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    looks aok, guess is late 1968 from those Dubellier caps , cheers
     
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  6. AndyD

    AndyD Well-Known Member

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    Thank you! I think you might be correct about the output valve socket. I will get back to you with some more photos a bit later on.
     
  7. neikeel

    neikeel Well-Known Member

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    Only bit I can see is the bias slider missing and subbed with a fixed 68k resistor.
     
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  8. Ned B

    Ned B Well-Known Member

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    The steel chassis 50W trems were always made that way, so they could go into either cab.
     
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  9. kuli

    kuli Active Member

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    Yes I still got it and it gets to go out on gigs every now and then - not often these days sadly.. Actually a guy from Italy helped me narrowing it down to maybe be from 1969 instead of 1968.
     
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  10. TAZIN

    TAZIN Active Member

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    Very nice condition. I also vote for late '68 or early '69. If the serial number prefix is "T/A" then I'd opt for early 1969.
     
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  11. AndyD

    AndyD Well-Known Member

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    The serial no. Is T/A 104##! So early ‘69?
     
  12. AndyD

    AndyD Well-Known Member

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    I’m curious to know what the absence of the bypass cap on V2 cathode suggests.
     
  13. Ned B

    Ned B Well-Known Member

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    It is the shared cathode circuit (pre-split). Those don't have the .68 bypass cap.
     
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  14. AndyD

    AndyD Well-Known Member

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    Sorry, are you saying shared V1 cathode = no bypass cap on V2?
     
  15. neikeel

    neikeel Well-Known Member

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    V1 is shared cathode
    You only see a 0.68uF on V2a cathode after introduction of the spilt cathode on V1 (mid 67 until about 1972).
     
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  16. TAZIN

    TAZIN Active Member

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    50 watt Tremolo amps can be a bit more difficult to pinpoint a manufacture date just like the Super P.A. and Super Tremolo amps. These amps tend to use more left over parts in their assembly which makes dating by features & components more difficult. Nonetheless, I'd still guess that it's early 1969 specially with a "T/A" prefix. I've seen other 50w Trem's with a T/A104xx serial number that were in the February - March 1969 zone.
     
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  17. Marshall50w

    Marshall50w Well-Known Member

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    My 50w Tremolo Head T/A XXXXA has the the inspection tag in it dated 01 06 1970.
    upload_2021-2-17_22-10-51.png
     
  18. TAZIN

    TAZIN Active Member

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    Your 50w Trem has the "A" suffix after the serial number which denotes a later build. Based on the June 1, 1970 inspection tag date I'd guess the serial # in the 7000A area.
     
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  19. Marshall50w

    Marshall50w Well-Known Member

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    Yes I think that the 'A' suffix denotes that the amp was built between July 1969 - Dec 1970. The inspection tag narrows it to 01/06/70. The other numbers denote the Production Number. My production first two numbers are 69XX
     
  20. TAZIN

    TAZIN Active Member

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    The use of the 'A' suffix started around the middle of April 1969. For example, T/A1041A has an inspection date of April 25, 1969. Additionally, the serial numbers started at 1000A instead of 0001A.
     

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