Original 1967 50 Plexi?

Discussion in 'Let's Talk Vintage' started by PaulHamwijk, Jul 5, 2019.

  1. PaulHamwijk

    PaulHamwijk Member

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    Hi All, I recently found myself a lovely 50w Plexi :)

    Can you tell me if its all original 1967, part from a re-tolex and repro logo? plexi - 1.jpg
     

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  2. PaulHamwijk

    PaulHamwijk Member

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    And some more pics
     

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  3. PaulHamwijk

    PaulHamwijk Member

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    and a few more
     

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  4. MoreAmpsPlease

    MoreAmpsPlease Active Member

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    Been inside a lot of old amps and that one is amazing. Not an expert on the serial number stuff, but just had to say "lovely" is a good word for that one!
     
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  5. Goldsmithmill

    Goldsmithmill New Member

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    I put my 50 cents on that it is a very early 68. Some of the mustards are dated last quarter 67 but a 67 would have had the serial number in a "window".
     
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  6. ampmadscientist

    ampmadscientist Well-Known Member

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    1. It's not really original. The whole circuit has been re-worked on the insides.
    The output tube sockets were replaced, power connector is updated, etc...
    This amp is a restoration job.

    2. You must install screen grid resistors for the output tubes, or the fuse will probably blow when the amp is cranked up loud.
    (or, somebody has installed over-sized fuses which is common)
    Remember I told you this when the fuse blows.

    Note: the correct HT fuse will be 500 ma (or) 1/2 amp slow blow.
    This fuse appears to be changed to an over-sized fuse 1 amp.
    This would have been done because the screen grid resistors are not installed causing the HT fuse to blow.

    This amp was built for a type of older output tube which has been updated and is no longer produced.

    Putting the newer type output tube in this amp will draw too much current and the fuse will blow unless the screen grid resistors are installed.

    Installing the screen resistors is relatively cheap and easy....
     
    Last edited: Jul 5, 2019
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  7. PaulHamwijk

    PaulHamwijk Member

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  8. TAZIN

    TAZIN Active Member

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    Very nice amp. Aside from the IEC connector it looks like the rest of the parts are untouched/original including the output valve sockets which are original. I'd say the amp is from the tail end of 1967 or possibly the begining of 1968.
     
  9. Nik Henville

    Nik Henville Well-Known Member Silver Supporting Member

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    Bloody
    lovely...

    ...regardless of resto/original.

    Gorgeous lookin' box - how does she sound?

    :hippie::uk:
     
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  10. boola1

    boola1 Well-Known Member

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    I would defer to Tazin on, well, everything but it just seems too clean to me. I wonder how an amp that needed re-tolexing can be so clean inside?

    On several of the photos I can see what looks like the remains of solder dye but it's always away from the join, like it has been re-soldered at some point.

    All the components check out as Tazin said for a 67/68 amp.
     
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  11. PaulHamwijk

    PaulHamwijk Member

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    She sounds lovely warm and smooth with a lot of balls and grunt! Paying her over a 1967 Pinstripe 100 cab ;-)
     
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  12. boola1

    boola1 Well-Known Member

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    On second thoughts, I think it's just solder flux. They didn't use dye at that point.
     
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  13. fifteenohms

    fifteenohms Well-Known Member

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    Paul that is one very nice find
     
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  14. neikeel

    neikeel Well-Known Member

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    I agree 100% with Tazin.

    It is an exceptionally clean and tidy, original early '68 bass spec amp.

    Everything about the layout and build (including the output tube sockets) is original. Only mod is the IEC socket.

    I serviced an absolutely identical one a few years back - I had to replace the octals as they had arc'd between heaters and anodes - they were the same unusual red type, same tone caps, same twin filter cans. It was a sweet, bluesy amp, not really a rocker but was headed for a studio that wanted that niche filled as they did not have a JTM45.

    Odd tho' why and amp that has hardly seen any service had to be recovered.

    AMS is right about the screen resistors, unless you have a nice matched pair of Mullards or BVA Brimars to drop in.
     
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  15. ampmadscientist

    ampmadscientist Well-Known Member

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    The soldering has all been re-done.
    But they did a neat clean job, I like it.
    Several of the parts have been replaced with (what looks like) accurate reproductions.
     
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  16. ampmadscientist

    ampmadscientist Well-Known Member

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    It's all re-soldered.
    Several parts have been replaced with accurate parts.
    The output sockets have been replaced.
    But they did a neat job which I like.
    They did such a nice job, it fooled a lot of people.
     
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  17. stickyfinger

    stickyfinger Well-Known Member

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    How can you tell if the joints have been redone? They look like they have age to them IMO.

    Not all the amps from this time frame have layout die on the joints an its is extremely hard to get all remnants of it off the joint either through soldering or cleaning the die.

    Amp is as clean as they get minus the headbox.
     
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  18. ampmadscientist

    ampmadscientist Well-Known Member

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    67 plexi.png
     
  19. stickyfinger

    stickyfinger Well-Known Member

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    Ok, so what should a 1968 untouched solder joint look like?
     
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  20. soundboy57

    soundboy57 Well-Known Member

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    I had a close to mint 67/68. No dye on the solder joints. I added a few pics for reference. One of the best sounding heads ever made :) Mine was a PA version, model 1985. Sounded lovely, but alas, I thinned down a lot of gear and it went to a good home.

    [​IMG]

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