More amp trouble - second SOS!

Discussion in 'Amps & Cabs' started by RVA, Nov 14, 2015.

  1. RVA

    RVA Well-Known Member

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    OK, thank you.
     
  2. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    RVA, Our house currents can vary from between approx 115 to 125 volts so transformers can yield higher or lower readings depending on what the house/venue etc outlet tests at. This is why people use a variac and a multimeter to precisely set the amount of volts the trans is getting and take readings off that. These are the volts that go thru the power cord and go to the "120 V AC" leads



     
  3. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    On that Fender tranny, 67, what did you find that caused it to fail? I saw you say a shorted tube. Were there other things that caused the tube to short?
     
  4. RVA

    RVA Well-Known Member

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    I used a Fluke meter very similar to 67plexi's. I had the power on and standby off. I checked in the 2 pin connector for each of the wire colors above. I checked the yellow wires 2x and verified my readings each time. I even flipped the negative and positive probes to each side.

    I am going to have a funeral for my dear old friend, then harness it's organs (tubes and cab with 18" speaker.) for a suitable donor. That you for helping me get closure on this and saving me from paying for a costly diagnosis.
     
  5. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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  6. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    Not sure what you mean here RVA, are you giving up?
     
  7. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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  8. syscokid

    syscokid Well-Known Member

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    In that case...
    I'm sending you my sincere sympathy to you in regards to your dear old friend... bon voyage... :sadwave:
     
  9. RVA

    RVA Well-Known Member

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    That seems to be 67plexi's recommendation, as finding the problem requires a point by point diagnosis.
     
  10. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    Your Peavey is a combo not a head, right?
     
    Last edited: Jan 23, 2016
  11. RVA

    RVA Well-Known Member

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    Combo. It has a very nice 12" speaker. I will experiment with it as a cab.
     
    Last edited: Jan 24, 2016
  12. RVA

    RVA Well-Known Member

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    It is ALIVE!!! (Frankenstein reference)

    [​IMG]
     
  13. RVA

    RVA Well-Known Member

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    This is a rather bad ass combination!
     
  14. 67plexi

    67plexi Well-Known Member

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    Use this voltage chart when testing a amp Voltage Chart.JPG
     
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  15. syscokid

    syscokid Well-Known Member

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    What is the row of B's for?
     
  16. 67plexi

    67plexi Well-Known Member

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    The B+ is your dropping string B+1= high voltage from power transformer secondary leads to first filter capacitor +
    then a 3-5 watt resistor to B+2 then the next filter capacitor + and so on. If B+1= 500VDC do you want 500VDC on your first preamp tube
    I don't think so more like 185-200VDC the dropping string is how this is done. B+1 & B+2 are hidden behind the large black filter capacitors
    B+3 is the green wire from the filter board to the phase Inverter B+4 is the next green wire to the overdrive channel B+5 is the 3rd green wire
    to the first input preamp tube.
    001.JPG
     
  17. 67plexi

    67plexi Well-Known Member

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    This is a gut shot of MEGA-PLX you can see the 10 watt 6000 ohm resistor on the filter board.
    not trying to brag but this is one of the best sounding amps ever. JTM-45 PT 1968 Marshall plexi OPT. Custom build 50 watt 001.JPG
     
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  18. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    Another good video from Mr Carlson

     
  19. chilipeppermaniac

    chilipeppermaniac Well-Known Member

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    The last video I posted shows a trick for removing those blobs of hot melt glue.
     
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  20. syscokid

    syscokid Well-Known Member

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    What are those little boards that are on the sides of the chassis, next to the guitar input jacks for?
     

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