Fender 5E5-B Schematic

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by K-man, Mar 5, 2006.

  1. K-man

    K-man Member

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    Anyone know where I can get the schematic for a Pro Amp 5E5-B? All I can find on the net is 5E5-A.

    I'm trying to restore the amp back to it's original state. Someone had converted it to a Marshall type circuit. They put in EL34 power tubes and all 12AX7 preamp tubes. Alot of the components differ from the 5E5-A schematic I compared it too, even components in the preamp.

    Thanks.
     
  2. Dave C

    Dave C Gold Supporting Member

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    Sorry Kurt, I dug pretty deep but I couldn't find a "b" either. Could these components be from the "marshall"conversion ? Or do they look too original ?
    Dave C
     
  3. Schwalbe

    Schwalbe Member

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    That's a new one on me. Can you post chassis photos? How does it compare to the 6G5? There might be some clues in comparing schematics from just before and after.
    Check your amp against the 5E5-A schemo and layout. The eyelets may be located the same in which case you can re-build it as an A type.
    A lot of Fender model changes involved only a couple resistors or caps.
     
  4. tonezoneonline

    tonezoneonline Member

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    New one on me too.I have 5B5 , 5C5 , 5D5 rev. I-ED , 5E5 marked #43 and 5E5A .Then it went to the 6G5.
    If any of these will help,email me.
     
  5. K-man

    K-man Member

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    The layout looks identical to the 5E5-A. Most of the components looked original. These were the differences off the top of my head:
    1. The filter caps were 30uf instead of 16uf.
    2. The grid resistors for V1 were 32k instead of 68k.
    3. All of the resistors between V1 and V2 were different values.
    4. A few of the resistors between V2 and V3 were different values.
    5. The negative lead to the selenium rectifier (what is that by btw?) was removed.
    6. An electro cap was added between one of the pins of V4 and ground.
    7. Some weird hollow tube-like thing was added between one of the pins of V5 and ground.
    8. A pot was added, maybe to bias the power tubes. I can't remember exactly how it was wired. There was a wire from the power transformer to the pot, then a wire from the pot to the pilot light and one to the board somewhere.
    9. One of the wires from the either the output transformer or chike was snipped off.
    10.The power tubes were changed to EL34 and all the preamp tubes were 12AX7.

    When I get home tonight I'll try and post some pictures.
     
  6. Dave C

    Dave C Gold Supporting Member

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    Kurt, from your description it sounds like this amp has had a lot questionable mods/repairs/hacks/slashes done to it over the years . I'd rebuild it as a 5e5a if info on 5e5b is as unavailable as it seems. Pics should be "interesting". Let me know if you need a hand with it.
    Dave C
     
  7. K-man

    K-man Member

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    Here are pics of the chassis:

    [​IMG]

    [​IMG]
     
  8. Dave C

    Dave C Gold Supporting Member

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    Hi Kurt, good pics, what's with that wire wound resister (green tubular gadget) , cathode bias perhaps ?How about that pot on the side of the chassis , hum balance control ? Does the selenium rectifier for the bias circuit still work ? Anyway the amp looks like a good candidate for a restoration project.
    Dave C
     
  9. redtoploader

    redtoploader Member

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    Sounds/looks like they cathode biased it(hence removing the selenium recto from the circuit and adding the cathode bias resistor with bypass cap) and took the choke out of the circuit...probably wanted to make it like a big tweed deluxe. Dave C is probably correct in noticing a hum balance pot?

    At least it looks like a fairly easy resto job, nothing too hacked. Get those dang el34s out of there pronto, what a travesty!!
     
  10. K-man

    K-man Member

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    I was hoping some of you guys could answer those questions...

    1. What does a selenium rectifier do? The wire you see next to it was removed and soldered to ground.

    2. So that green thingie is a wirewound resistor? Should I restore it to fixed bias when I put the 6L6 tubes back?

    3. Assuming that pot is a hum balance control, should I just leave it in?

    Thanks.
     
  11. ES350

    ES350 Member

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    Terminate all the mods with extreme prejudice...BTW, is that a stock OT in there? (the leads are wrong).

    Lose the selenium rectifier---use an IN5004
    Restore to fixed bias
    Lose the hum balance and all the trash parts

    Those are great amps (I have two) with a very unique sound and they are increasing in value every day. Do the right thing...
     
  12. brad347

    brad347 Member

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    i have to agree with ES-350, I'm way in favor of keeping things all original.
     
  13. Dave C

    Dave C Gold Supporting Member

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    Yeah, terminate the mods with extreme prejudice......I like that, good one ! Selenium rectifier is an older form of diode (makes ac into dc)and in this application was used just for the bias supply. If it still works I'd use it , if it doesn't change it to a diode as ES350 suggested . I'd restore it to fixed bias and if that pot on the side is of the appropriate value I'd use to make it adjustable fixed bias . Please do a cap job......those caps are 50 yrs. old and definitely on borrowed time. Those el34's look like Amperex logo and would probably be good for another amp,just not this one.
    Dave C
     
  14. K-man

    K-man Member

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    Thanks for the help guys. Unfortunately, I don't think the PT is original. I'm guessing whoever did the EL34 mod changed the PT.

    I plan on following all your suggestions. I'll do a cap job, change the resistors to the correct values, and rewire to a fixed bias supply with 6L6's.

    Dave I may give you a call in a week or so about wiring the transformers... Not sure if I can handle that on my own.

    Yeah, power tubes are Amperex Bugleboys. If the owner doesn't want them back I can put them to good use!
     
  15. ES350

    ES350 Member

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    That's a Triad 8087 in the picture---original PT in that amp. The OT may have been swapped for EL34 impedance and/or the original was blown. There are a number of suitable replacements available...
     
  16. K-man

    K-man Member

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    Does that mean I have to change the OT when I switch back to 6L6's?
     
  17. ES350

    ES350 Member

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    Maybe---I don't know for sure if the OT was changed, although the leads look wrong from what I can see in the pix. The PT is original--keep it in there. Check the OT to see if it's original---EL 34 and 6L6 have different primary impedance requirements and 6L6 will sound and perform best with a OT designed for 6L6's. I would run this by a good tech familiar with tweeds if I were you...it's worth it.
     
  18. K-man

    K-man Member

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    The OT was definately re-wired, you can see one of the leads taped off in the picture. I'll check the code tonight.
     
  19. K-man

    K-man Member

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    The output transformer was definately changed. I can see the old mounting holes in the chassis for the original transformer. The transformer code is:

    560039
    CIN-TRAN 1641
    30-8213

    I googled it but didn't come up with any info. How can I tell what the impedence of the transformer is?
     
  20. Dave C

    Dave C Gold Supporting Member

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    You would have to calculate the turns ratio of the transformer and using the result determine the primary impedance resulting from the ratio and speaker load. There is some math involved and I could tell you over the phone far easier than typing a long explanation here. Maybe someone else could chime in with a better shorter version than what I'm thinking of. You've got my number.
    Dave C
     

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