Maintenance Job - 1970 Super Bass

Discussion in 'Let's Talk Vintage' started by Marshallhead, Dec 5, 2016.

  1. Marshallhead

    Marshallhead Well-Known Member

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    Job for tonight - new electrolytics for this old warhorse. Still has its original Eries at the moment.
    [​IMG]
     
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  2. Kris Ford

    Kris Ford Well-Known Member

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    My '74 is going in too, still has it's originals too, which I'm getting a crackling and staticy noise.
     
  3. neikeel

    neikeel Well-Known Member

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    Preventative maintenance or are they dying?

    Are those F&Ts or the MA ones?

    Interestingly I had a new ARS dual 16uF die on me in my offset clone after a few hours. Started smoking first (yes, you now the smell!) hot to the touch so that is how `i could tell it was that component smoking. Dropped in a new F&T 32/16 and all well at the moment.

    Good luck.
     
  4. Marshallhead

    Marshallhead Well-Known Member

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    The amp has not been used for a few years aside from an occasional soft power up on a variac, so some preventative work before something goes wrong. I used MA caps.

    Job complete - pic below.
    [​IMG]
     
  5. Marshallhead

    Marshallhead Well-Known Member

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    And the ones I took out. 5 Eries and a later Daly (I recall it had a bodge up in place of one can when I acquired it about 15 years ago and I put the Daly in there!)

    [​IMG]
     
  6. Marshallhead

    Marshallhead Well-Known Member

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    Only problem I encountered is - I think the thermostat in my solder station must have gone bad - I suddenly noticed the tip and shank glowing red hot, even when I set the temp very low!

    I had to keep switch it off between shots and working very quickly when I did switch it on to use it.
     
  7. neikeel

    neikeel Well-Known Member

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    I have a Weller WTCP51 and I have been warned that this can happen to these if the magnet does not separate cleanly in the tube (alternatively can cut out if the contacts get oxidised otherwise they are pretty reliable) is yours one of these?
     
  8. Marshallhead

    Marshallhead Well-Known Member

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    It's Maplin's own brand - but I think it's made by Weller. It has model no ZD-916 on it.

    When you say the magnet in the tube - what am I looking for?
     
  9. stickyfinger

    stickyfinger Active Member

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    Do you have a capacitance meter?

    It would be interesting to see what they measure to be able to compare how much of the "softness" or "mellowness" of old amps are contributed to the worn, presumably low filtering of the 40+ year caps.

    How the tone of the amp now?
     
  10. boola1

    boola1 New Member

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    I've done the filter caps on all my old amps (40+ years) and it definitely makes a difference. It tightens things up and increases the clarity of the amp. The change isn't huge unless the caps were really knackered and I've never regretted changing them, the amp always sounds better.

    PS, I use Mundorf caps which some people might question but my ears approve!
     
  11. Kris Ford

    Kris Ford Well-Known Member

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    So if you want to go for a "tight, metal spec" tone, which is the recommended cap for the job?

    Soft and mellow I DON'T want..total aggressive metal panel tone is what I crave.:hbang:
     
  12. boola1

    boola1 New Member

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    I have tried F&T, ARS and Mundorf. Of those 3 I would go for F&T.
     
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  13. neikeel

    neikeel Well-Known Member

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    On my weller it is the tip and the part just behind the tip which determines the temperature at which it cuts out. The part behind the tip is spring loaded and makes electromagnetic contact with the tip (inside the hollow barrel) when it hits the correct temperature the tip loses its magnetic effect and the contact is broken. Simple but effective as long as the plunger can slide inside the barrel. Yours may just be a theremostat that has gone south looking at the pictures. I guess the question is whether it is the station or the pencil part that has stopped working. I have a cheap nad cheerful Weller 25w with fine chisel tip that I use for desoldering jobs, that always works (well until I jinxed it).
     
  14. Kris Ford

    Kris Ford Well-Known Member

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    Cool, thanks!
    What's the opinion on JJs?
     
  15. neikeel

    neikeel Well-Known Member

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    I prefer LCRs when I can get them, F&Ts are fine as are ARS, I also like RIFAs, only had a couple of JJs and one blew up on me (ok so an ARS has too now) each time the cap - not my wiring as the replacements have been fine. Just my :2c:
     
  16. Marshallhead

    Marshallhead Well-Known Member

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    My meter does capacitance but you have to dunk the legs or tags into little slots on the body of the meter and the cans don't allow that!

    The amp sounds tighter now, the chronic ghosting that afflicted it before has gone, although it still has a 100Hz hum behind the note on single high notes when cranked right up. It doesn't interact with the note and give the ring modulator effect you often get with ghosting however.
     
    Last edited: Dec 7, 2016
  17. pleximaster

    pleximaster Well-Known Member

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    F&Ts are good as Rifa for new ones but the best ones I have tested are Frag Jan Zuerst (Specially mad for him by F&T) great for odd values as well.

    plexi
     
  18. matttornado

    matttornado Active Member

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    Just re-capped my 74 Superlead w/ F&T 50/50s & the amp sounds great! Doing maintenance as well. That along with a fresh quad of Ruby EL34 BSTRs. Sounds killa!
     
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  19. Kris Ford

    Kris Ford Well-Known Member

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    My '74 is going in soon!
    I don't do my amps, best to leave with the pros. I can build a LP wiring harness from scratch, wire a cab, etc, but won't go inside my amp..I simply don't trust myself.
     
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  20. boola1

    boola1 New Member

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    A cap job is pretty easy if you're OK with a soldering iron. The only tricky bit is the cap which is mounted under the board, that always gives me grief!
     

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