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1955 narrow panel Fender Pro repair help

Discussion in 'Amp Central Station' started by Kerry Vance, Jun 10, 2008.

  1. Kerry Vance

    Kerry Vance Tele-Meister

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    I have a December 1955 narrow panel 5E5 Fender Pro that needs repair. A friend loaned it to me. When I first turned it on, smoke came out and I immediately turned it off. Neither the power transformer nor the output transformer were hot. Turns out the amp hasn’t been played in several years and I’m hoping the problem is the filter capacitors. I can see a bit of debris under one of them where it looks like a cap has erupted. I know all about the disclaimer on discharging caps before working on the amp and I will do that. Now, I need help in getting everything together to replace the filter caps. The rubber stamp on the tube chart is EK, making it December 1955. The tube chart shows it to be a 5E5, but it has knobs for treble, bass and presence – which I think means it is at least a 5E5A. Here's a schematic:

    http://www.schematicheaven.com/fenderamps/pro_5e5a_schem.pdf

    I would appreciate recommendations on the caps to use. Is it correct that I am replacing five capacitors, those being (3) 16 microfarad/450 volts, (1) 8 microfard/450 volts, and (1) 100 microfarad/25 volts? And, in the case of replacement values – can I go with 16 microfarad/475 volts? And, what about the other two caps? I certainly appreciate any and all help. I'm posting this request for help on the Weber amps board, too. I need all the help I can get. Thanks in advance. Oh, I didn’t mention that the Pro has a JBL D130F.
     
    Last edited: Jun 10, 2008
  2. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    What a sweet amp to be nursing back to health!

    Not only can you use 475V caps, you should because of the higher voltages they're seeing these days. I'd personally seek out 500V or higher-rated caps for the first few.

    - Scott
     
  3. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    Take a photo of the guts. This will help us figure out if it's an earlier or later narrow panel Pro.

    In either case, if it's a filter cap, a 16uF will work. I'd have it taken to a shop though. Have them replace all of them old caps, this will also include 25uF cathode bypass caps in the preamp. If it is a later Pro (5E5-A) there'll also be a 8uF that'll need replacing.

    Hopefully nothing was taken out with the failing cap. They get old and dry out over the years and can fail.

    You can go with higher valued caps if you (or your friend) want to tighten up the bass and go for even more noise reduction. If the old untwisted heater wiring was followed, you can have the shop rewire em twisted to reduce noise as well.

    In any case, replacing the old caps, even with similarly valued ones, will likely make the amp sound slightly different. Old, dying caps tend to sound different than new, fresh caps.
     
  4. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    Forgot to mention, you may want to ask the repair guy to measure all of the resistors to see if they've strayed over the years. +/-10% is OK, but any more and you may want to have the straying resistors replaced.
     
  5. Kerry Vance

    Kerry Vance Tele-Meister

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    Here's a photo

    [​IMG]

    Thanks for the help.

    Kerry
     
  6. Dacious

    Dacious Poster Extraordinaire

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    As old caps could vary by 10% or more in value getting '16' mfd caps is not vitally important. Anywhere from 10-22 would be good.

    That amp has already had one replaced - that tin metallic yellow cap isn't original.

    Johhny's suggestiong is a good one: find an old radio or TV repairnan if you can. There are some other things in an amp not fired up in a while that need attention to, or the hums, buzzes and crackles will drive you bananas.

    The smoke was probably a cap, but your transformers should be checked for leaky windings with a megger.
     
  7. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

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    Once you let the smoke out of those caps, they stop working.
     
  8. Tim Swartz

    Tim Swartz Friend of Leo's

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    Shoot, new ones are often more than 10% off....caps in a 50 year old amp could easily be 100% off.
     
  9. sjhusting

    sjhusting Tele-Afflicted

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    The filter caps don't look original to me either.

    steven
     
  10. Kerry Vance

    Kerry Vance Tele-Meister

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    So, is the general consensus that I should not attempt this repair myself? I've never tried this sort of thing before, but I can solder cleanly and can read a VOM. I've considered buying amp kits and this seemed like a way to ease into that. Thanks for the advice.

    Kerry
     
  11. FiddlinJim

    FiddlinJim Tele-Holic

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    Kerry, just my dos centavos, but if I were in your shoes with such a treasure of an amp and little experience, I'd seek out a pro tech that would let me watch and talk me through what he's doing. That way, you can learn quite a bit with minimal risk to the final product. Then go build yourself a Deluxe!

    I'm not trying to discourage you; you can probably do the job on this 5E5, but an "oops" with a brand new kit is lots easier to stomach. I've built 3 amps (including a 5F4, essentially the 5E5A circuit) and I've made my share of mistakes that I would rather not make on a vintage amp.

    Maybe somebody reading this that's around Dallas could recommend somebody who would be willing to let you observe.

    Jim
     
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