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  1. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    The only hitch with this method is you’re measuring the screens as well. The screens draw approximately 3-5ma. That’s no big deal though.
  2. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Ohms law says if you measure voltage across a 1ohm resistor it’s the same as ma. DVM is set to mv. And across the 1ohm resistor toe two will be the same. ma and mv.
  3. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    It’s for biasing the power tubes. The wires from the jacks between the transformers go to pin 8 before the 1ohm resistor so you can measure the ma in mv. With a DVM, you put one lead to the jack and the other to ground, the result is the current flowing through the tubes at idle in mv. The...
  4. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Little more work
  5. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Just heaters and the power tubes are done. Added jacks for biasing
  6. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Inputs and the pots side is done
  7. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    getting the power tubes wired up.
  8. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    The screen resistors take a beating in old Fender amps. I like using the Vishay 3watters.
  9. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Not really happy with the grounding of the pot components, but it’s done now, don’t want to re do it now. Anyway it’s the weekend and it’s like 110 degrees outside so I’ll be here with the amp moving forward .
  10. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Thanks, worked in it last night but didn’t get any pics taken, but I will. Looking like I ready for the turret board to go in and start connecting to sockets and pots.
  11. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Little more work, started on the inputs and I also got threaded nylon standoffs and nylon screws. The board mounting wasn’t fully thought out and had gotten a little too close to the HV cap
  12. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

  13. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    👍 Won’t be using 34s. I have the RCA 6L6GCs for it dated 1961
  14. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Thanks for the 100k/82k tip I’ll try that in the future. The owner opted for new tubes. Anyway, worked on the amp this weekend. Incorporated. Some of the grounding scheme, but didn’t stay true to it. Got some nylon hardware coming to use for the turret board close to the HV cap and V1 plate...
  15. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Yes, you are correct with everything you just said. I’m a mechanic and frequent pawn shops and can’t resist a good tool, I repair aircraft structures so the sheet metal tools are plentiful, and you don’t even want to know how much Impaid for some of them. I am teaching my son how to use them...
  16. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Finished up on the pro, needed all new electrolytic caps and a new set of power tubes. They were too far apart and mismatched by brand. One tube was 11.2w and the other one was 15.6w, not very good Anyway,I didn’t like the double pull switches, too big and the bias board wouldn’t fit past...
  17. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Yep, it will be in typical fender style. Anyway, it’s slow going, had to put it aside, got a 1962 Brownface Pro to repair.
  18. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Kinda slow going but started to wire in the PT. And made the bias supply board. Found a tubular rivet setting tool for my hand squeezer to set the eyelets and I also have a heavy duty 1/8” hole punch for punching the holes in the eyelet board. Learned something on old transformers, the wires...
  19. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Fender sure does know how to make a quiet amp. I’m hoping that when I incorporate the grounding scheme with a few exceptions that the amp would have minimal or even no hum. Vintage fender amps are my favorite amps to work on.
  20. Rotorcraft230

    building a Fender "Pro-Amp" from scratch

    Thanks ELS, that sure is a lot to take in and I already practice some/most of that, but let’s remember it’s not a 10,000 $$ hifi amp, it’s a guitar amp. And like I had said in the past he doesn’t mind hum, as long as it’s not excessive it’s not a problem. I’m an amateur builder and I’m...

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