Changing the electrolytics in a tweed Fender

Discussion in 'Amps and Cabs' started by Ed Reed, Jan 22, 2008.


  1. Ed Reed

    Ed Reed Senior Member

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    I own a 55 Tremolux, I just bought the caps to replace the originals. Anyone care to coach me through changing them in the amp?
     
  2. SatelliteAmps

    SatelliteAmps Member

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    It's fairly straightforward. There are well drawn layouts that show where everything goes. You can find it at The Fender Amp Field Guide.

    http://www.ampwares.com/ffg/

    Look up your amp, and there should be a schematic and a chasis layout.
     
  3. MisterAgreeable

    MisterAgreeable Member

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    Hi Ed,

    This kinda obvious, but I thought I'd throw it out just in case : discharge the old capacitors before you begin work.

    Best of luck.
     
  4. JubileeMan 2555

    JubileeMan 2555 Member

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    First, make sure you've drained the caps of any dangerous Voltages.

    Unsolder all connections of the electrolytes highlighted in RED.

    Replace the caps making sure the ORIENTATION of + and - is exactly how they were placed before.

    Thats it. The GREEN caps are electrolytes as well...but I STRONGLY recommend you only replace the power caps that are RED. The Green ones should still be working strong.

    [​IMG]
     
  5. ajchance

    ajchance Member

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    My compliments on the instructional post Jubilee - that's the most useful post I've seen when it comes to a cap job. That would have saved me mucho time on the net if I'd seen it!

    What's the rationale for not replacing the green electrolytics in your diagram? I thought that all electrolytics fall under the same concern of degradation.
     
  6. Ed Reed

    Ed Reed Senior Member

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    WOW!! That was very kind of you. This will be my first attempt at "servicing" an amp and I want to do it right for

    1 I want to live through it
    2 The amp is vintage and can't be replaced.

    If it is ok I will be touching base with you throughout this whole process.
     
  7. JubileeMan 2555

    JubileeMan 2555 Member

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    Not a problem. I was a real novice to all this not too long ago and I like to take what i've learned and show others as I would like to have been shown:)
     
  8. SatelliteAmps

    SatelliteAmps Member

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    I would also change the bias cap. That would be the first green one on the left.
     
  9. bosstone

    bosstone Member

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    Just another point of view from the opposite side; I was lucky enough to come across a 1950s White amp. For those who don't know and I didn't at the time, Forest White was a partner of Leo Fender's . The amp is electrically almost identical to a Tweed Champ but it has a tone knob. Everything was original in it including the caps. I took it to a tech who has been working with tubes since working on missile systems with tubes back in the 60s. I won't mention his name but I respect his work and he has been mentioned positively on these pages in the past. He tried to convince me that I had to change the capacitors but I didn't see any evidence of leaking and was willing to take the chance. He agreed to ramp the input voltage up slowly with a Variac. When he was done he called me and raved about the sound. He was so enthusiastic about it that he called some musician friends to come over to have a listen. He told me that it sounded better than any Champ that he had ever heard and that he had serviced several that had been used in recording studios. The amp wasn't dead quiet but it was well within the range of acceptability. I am no expert and this might just be a fluke but for me, I don't replace caps and other parts until I know for a fact that they are bad. I'd be really curious to know how many great old capacitors and tubes have been thrown out because someone was told they were bad just based on their age. Of course, I took a chance and a cap could have blown up and done damage to other parts in the amp but...
     
  10. Ed Reed

    Ed Reed Senior Member

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    I am replacing all the above colored caps. Also getting rid of 2 orange drops that were added at some time in the past.

    bosstone, thanks but I'll give up some tone for the sake of keeping that output tranny. I just can't risk it.
     
  11. SatelliteAmps

    SatelliteAmps Member

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    The White Amp is actually a Tweed Princeton, not a Champ. They are great amps. Got a few myself. Seen a number Fender amps over the years that people got, and didn't want to change the old capacitors on. Some were fine. Some had to have a transformer rewound or replaced. I've never had one come in that didn't sound amazing after replacing the caps. Their is no gain in tone by keeping the old caps if you replace them with correct value new caps.
     
  12. bosstone

    bosstone Member

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    I have definitely heard amps that came out sounding worse after a cap job.
     
  13. SatelliteAmps

    SatelliteAmps Member

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    Then I would find a new tech.

    Replacing the original filter caps with the correct value shouldn't make an amp sound worse. Using the wrong value, or the wrong type will make an amp sound worse, which is done by a lot of hacks. Especially when they don't have the correct value.

    The potential for damage to the transformers in an amp because of old filter caps is more than I am willing to accept. There is no benefit tone wise to keeping them. Benefits to changing them include transformer protection, less ac ripple and hum, correctly biased and working tubes.
     
  14. bosstone

    bosstone Member

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    There definitely some techs out there who don't use high end caps or the older stuff actually sounds better. I have never had a cap job done but I know people who have whose amps came back sounding like crap. I sold a really nice Supro Thunderbolt to someone. A couple of months later, a tube went out. He took it to a well know tech who many think is great. Personally, I think he would rather recap or modify an amp than fix one properly. At any rate, the tech talked the guy in doing a recap job. The guy called me back to tell me how the amp no longer sounded good. He was highly disappointed and I suggested he go back to have it fixed correctly. He did and it still sounded like crap. Finally on the third try the amp came back sounding like it should. Whenever I see an old amp for sale that has had a recent cap job I cringe because from my experience, it usually won't sound as good as one with all original parts that are in good working order. Some people seem to think that food suddenly turns bad the moment it has reached the expiration date and it ain't necessarily so.

    I can certainly understand your reluctance to take a chance with your amp and that is totally cool with me. My point was not to change caps just because of their age. If they are bad fine, go ahead. I only go to good techs who have as much respect for older amps as I have and they know to replace bad parts with ones that are of equal or better sound quality. I almost immediately take any amps I purchase to them to have them fully, serviced, checked out and make sure the tubes are good and that the bias is set properly. After that if an amp sounds great, I don't mess with the capacitors.
     

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