Ceriatone 5E3

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Stevo57, Jul 29, 2006.

  1. Stevo57

    Stevo57 Supporting Member

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    Nooby problem.
    I've been trying to complete a 5E3 build with no success. It's a Ceriatone 5E3 complete chassis. I only had to add the tubes and transformers. I'm using a Weber PT and a Mercury Magnetics OT. Both are brand new. After connecting the iron I get the correct voltages to the tubes, heaters, etc.
    Checked my wiring , again, and again.... Tried different known good tubes.....
    I still get no sound. How do I test the OT? What readings should I get?
    Thanks for any help, including the name of a Norcal amp tech possibly.
     
  2. WaltC

    WaltC Member

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    There are lots of things it could be. Have you tried to trace the signal from the input through the amp? If you're in or around the Sacramento/Roseville area I'd be glad to take a look and see if I can help.

    call Lincoln Street Music
    105 Lincoln St.
    Roseville, CA* 95678
    916-786-5761
    Ask for Walt...<G>
     
  3. Blue Strat

    Blue Strat Member

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    If ALL voltages are correct, I suspect the OT wiring to the output jack. But this is assuming that about 100 other things are correct. Since the prebuilt stuff may have never been tested (no trannys), it's even possible that THAT stuff isn't working correctly.
     
  4. Stevo57

    Stevo57 Supporting Member

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    Thanks for the replies Walt and Mike. The voltages I've checked are those that are related to the PT taps to the 5Y3 and 6V6's. I've checked the solder joints and routing from the builder and rechecked my own. I don't know how exactly to check the signal as you stated Walt. This is my first try at the innards with a few small exceptions. I'm determined to learn how to check and this build is determined to teach me! :eek:
     
  5. Blue Strat

    Blue Strat Member

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    Check preamp voltages too. Are the tubes KNOWN to be good in another amp?
     
  6. Stevo57

    Stevo57 Supporting Member

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    Mike,
    The only tube I'm unsure of is the 5Y3 as my other amp uses a GZ34.
    Is it safe to put a known good GZ34 in just for the purposes of testing?
     
  7. Blue Strat

    Blue Strat Member

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    If your voltages are within 5%, your 5Y3 is ok.

    Just for laughs, put the tubes back in your other amp and see if they're ok.

    Getting any voltage on the cathode resistor for the 6V6s?
     
  8. Stevo57

    Stevo57 Supporting Member

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    Tubes work in the other amp OK. I get voltage on the cathode resistor.
    How much should I be getting approx. ? When I say no sound I mean nothing. Not even a hum. The OT is wired with the center tap on the primary side to the 5K resistor , the other two taps are wired to pin 3 of each 6V6. The secondary side only has one self lead going to the positive pin of the speaker jacks.
     
  9. Blue Strat

    Blue Strat Member

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    Tell me about the secondary again? There should be 2 leads....MUST be 2 leads!
     
  10. Stevo57

    Stevo57 Supporting Member

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    The insulated lead is soldered to the + side of the speaker outs. The unisulated lead was factory soldered to the frame of the OT.
     
  11. doc

    doc Member

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    I'm sure Walt was talking about using an oscilloscope and hooking up an audio signal generator to the input and then marching through the amp to see where you lose the signal. I think there is a copy of Jack Darr's old book on guitar amp repair on the net - try Googling for it for more details.
     
  12. Stevo57

    Stevo57 Supporting Member

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    Thanks Doc, Walt, and Mike for your input. It looks like I'll need to have a real tech take a look at it. I don't have the experience or test equipment to sort this one out, and I do want to play it someday. I'll take you up on your offer Walt if I can't find a local guy soon.
     
  13. WaltC

    WaltC Member

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    So wait a minute <G>. You're saying that the Mercury Magnetics OT that you bought from them has the OT ground lead soldered to the frame of the transformer! that'd really surprise me. It is often necessary to swap the leads on the secondaries on an OT or switch the negative feedback loop from one tap to the other depending on how the amp is built and that'd be impossible with the OT (practically speaking) you've got. Plus I've *never* seen (in twenty or so OTs from Mercury Mag.) any OT wired like that.

    Hmmmm......
     
  14. Stevo57

    Stevo57 Supporting Member

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  15. WaltC

    WaltC Member

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    Wow! I stand corrected. I wouldn't like that personally, but it should still work. (you'd need to swap the brown/blue leads on the power tubes to correct any positive/negative feedback issues, works...). I've not used Mercury Mags for the smaller trannies I've used, most have been Hoffman or Hammond, and all the larger ones I've gotten from Mercury have discrete leads.

    there are a number of ways to trace the signal. the simplest and most low tech (and most dangerous) is to plug a sound source (cd player, etc.) into the input jack and hook up a "probe" (cap and ground) to a instrument cord into another amp and touch the probe to the (LOW VOLTAGE, SIGNAL SIDE ONLY!!!) low voltage signal sources (wiper on the volume pot, treble pot out put lug, input (low voltage downstream of the coupling cap) to the P/I to see where the signal exists/doesn't exist. You should get a good signal at the input jack, then trace from there.

    The RIGHT way to do it is with a suitably insulated/isolated ocilloscope probe and use the O'scope display to check for the signal. The bonus of using the O'scope is that if there is any spurious noise, ocillation or other bad artifacts in the signal they'll show up on the 'scope too. Plus you get to see the relative gain from each stage on screen.

    Like everyone has said though, so many things can be wrong that a meticulous, connection-by-connection trace all components from (my preference) the power side to the input side may be needed.

    Walt
     

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