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50's Danelectro Tube Tremolo (Vibrato) circuits, Octal tube, which?

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  • 50's Danelectro Tube Tremolo (Vibrato) circuits, Octal tube, which?

    For those familiar with those type of amps, which octal tube did they tend to use for the trem circuit?

  • #2
    they used the 6au6 in some but it's a 7pin tube.

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    • #3
      Are you asking out of curiosity or are you trying to find out what tube goes into a specific amp?

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      • #4
        It's a specific amp, but there is 0 info nor a schematic. It's a Wabash Deluxe from the 50s. It came in dead with the tubes in the wrong sockets, wrong tubes, etc.

        I figured out what tube type went where by testing the pin out, new caps , new star ground and a few other things and I got it working again, but the Vibrato tube is some sort of Octal power tube with standard 6L6/6V6/etc. type pin out, 2=H 3=P 4=G2 5=G1, I have no idea what specific tube. In any case it isn't working, and its not an optocoupler type setup, it's all done with that tube like many others did with smaller tubes.

        I'd be willing to bet it is a Valco, it is not dissimilar to some Harmony and other amps I've seen, so I figured there would be some Valco/Dano expert who might have an idea.

        Not sure on the Rectifier either. It came in with 6V6s (in the wrong slots) and a 5Y3. It doesn't bias anywhere close to correct, nor are the DC heaters on the preamp tubes, which are drawn from the bias tap correct, with those tubes, but it biases correctly with the right heater voltages (series heaters) with 6L6s, and the PT doesn't get hot from the current draw so that seems right. 5Y3 in a 6 tube amp with 6L6s....don't think so. Not sure what would have been correct for it though; 5U4 draws a lot of current, GZ34 would raise the voltage quite a bit. There may be some vintage rectifier I don't know about with that pin out that is supposed to be there.

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        • #5
          So the trem tube is for the low freq osc? Is the socket wired for a single or dual section tube?

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          • #6
            he said it was wired for an octal power tube like 6L6.

            Try various power tubes there and see. 6V6, 6K6. Doesn't seem like 6L6 would be used, but try it.
            Education is what you're left with after you have forgotten what you have learned.

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            • #7
              Single. As I noted, heater at 2, anode 3, 91ohm resistor between anode and G2 at pin 4, G1 at pin 5. Power comes in at the screen grid, so the plate voltage is lower.

              I traced the thing tonight, looks like this tube functions in conjunction with a 6SJ7 to produce the vibrato effect across the coil of the field coil speaker. Has to be really, the rest of the amp is isolated from it. I tested all the resistors, caps, pots, grounds, everything is within tolerance and functional, at least on the meter.

              I'll see if I can scan and post my crappy hand drawn schematic of the trem circuit.

              I only have the common tubes on hand. I'll see if I can get my hands on some less common vintage octals with that pin out. I was hoping someone would have seen similar to narrow it down, there were a few Valcos I found pics of on the web that at least had a family resemblance to the control layout. I've seen some references to some of them using a 6SN7 and a 6SJ7 together, but the pin out is wrong for the 6SN7.

              Rectifier: GZ34 is a no-go, voltage too high and bias is off, not to mention it makes the amp noisy. 5U4 also a no go, the heater current makes the PT get hot. It seems happy and quiet with the 5y3, so for now its staying in unless I find out about some higher current ability, rare, vintage recto tube with the same pin-out and voltage multiplier.
              Last edited by wizard333; 09-19-2014, 05:34 AM.

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              • #8
                Originally posted by wizard333 View Post
                I traced the thing tonight, looks like this tube functions in conjunction with a 6SJ7 to produce the vibrato effect across the coil of the field coil speaker. Has to be really, the rest of the amp is isolated from it.
                I've not seen that before. Interesting, fluctuate the magnetic field to produce tremolo. Cool. Keep us informed.

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                • #9
                  Crappy hand drawn Schematic below:

                  Click image for larger version

Name:	WabashDeluxeTremSchematic_zps5dea647d.jpg
Views:	2
Size:	43.6 KB
ID:	835408

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                  • #10
                    If you want, email it to me and I'll try to post it. gui_tarzan@yahoo.com
                    --Jim


                    He's like a new set of strings... he just needs to be stretched a bit.

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                    • #11
                      So does anyone know of an amp with a similar setup to the schematic I posted, maybe one with a schematic and tube chart available? Anything jump out as to what tube it might be or why it might not work? I tested all the resistors/caps/pots all appear to be functional within their parameters.

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                      • #12
                        6SJ7 maybe.
                        http://www.r-type.org/pdfs/6sj7.pdf

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                        • #13
                          The earlier Gibson GA-40's used a 6V6 and half of a 6SN7 in the Tremolo.

                          I had to make a new drawing, in order to troubleshoot one of mine ('54), and I've attached that drawing.

                          Jack
                          Attached Files

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                          • #14
                            6SJ7 maybe.
                            No, wrong pin out, see above.

                            I did try a 6v6 but it didn't work. I can't find any non working components either. Do you remember what you saw change at the pins when the controls were manipulated, voltage wise?

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                            • #15
                              Click image for larger version

Name:	WabashDeluxeTremSchematic_zps8de714cc.jpg
Views:	2
Size:	43.6 KB
ID:	835537

                              Updated/corrected schem attached. I honestly don't know how this would work, but that is how it is wired.

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