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First build 5F2-A: low output

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  • #31
    6V6GT
    3) 294 V
    4) 241 V
    5) 1.25 V
    8) 14.75 V
    2) 461 ohms.
    Means cathode current is 32mA

    Which across
    1) 284.8 ohms.
    will drop 9V , and that if we assume all current is going through that plate.
    Discounting a few mA screen current, voltage drop across transformes must be significantly less than 9V , and in fact compatible with Marc Dillardīs
    Check your wiring from point A to the OT to pin 3 of the 6V6. No way you should have a 74 volt drop through the primary of the OT. Should be 5 to 10 volts.
    Yet you report 74V , so do what he says.

    This alone hints at a gross wiring error, so signal injection and such must be delayed until this is solved first.

    And please post schematic here inside the thread
    Juan Manuel Fahey

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    • #32
      There are a couple of resistors on top of the chassis, and wiring, looks like heater wiring running to them. what are they for?
      The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.

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      • #33
        JD check these out:

        Automatic Wire Stripper WS39 - Cleaveland Aircraft Tool

        I got a pair last year. They strip like a champ and don't nick the wire. I found out the hard way, though, they don't strip the mil spec teflon coated wire, it just rips one side of the insulation off, but will work on your chassis wiring just fine.

        Pretty cheap too.
        The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.

        Comment


        • #34
          First, let me just say that my Princeton is now working and sounds amazing.

          Second, and more importantly, let me offer a heartfelt thanks to all who helped me troubleshoot my problem and all who made suggestions for improving the quality of my work. I learned quite bit during this build and much of it was from listening to you guys with your suggestions and tips. I plan on cleaning up my work in the next week or so. Thank you all so much.

          Finally, ahem, I'll reveal the source of the problem. Feel free to laugh or roll your eyes; I did both. The secondary on the OT has three wires: black, yellow, and green. I hooked the black and yellow up to the output jack according to the schematic during the main part of the build. Afterwords, I set up a ground wire (from a piece of romex) to solder all of the ground connections to and then attached it to the chassis lug. During this I attached the green wire from the OT to ground, despite the green wire not appearing on the schematic at all. I assume it was a center tap on the secondary and was shorting my signal to ground. I removed it (and capped it) tonight and the Princeton came alive. 😄

          Again, many thanks! I love this group. You guys are nothing but helpful and it is greatly appreciated.

          Jim

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          • #35
            Originally posted by JDodd View Post
            The secondary on the OT has three wires: black, yellow, and green...
            Not a "Center Tap," more likely a second tap for a 16R-speaker (assuming you have an 8R in it now). The original Princeton wouldn't have had one, as it was a "student" amp, but most kits & clones will come with at least two taps for different speakers nowadays. Easiest way to find out is get the docs from your OT manufacturer.

            Justin
            "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
            "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
            "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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            • #36
              Congrats Jim!
              The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.

              Comment

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