Announcement

Collapse
No announcement yet.

Run a 6ca4 rectifier on a 5v/2a wind?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Run a 6ca4 rectifier on a 5v/2a wind?

    Has any one tried it?
    I'm in the planning stage, thinking of using a Hammond H300519 power xfmr (500v ct, 100 mA; 6.3v, 3A; 5v, 2A) . I want a lesser diode, so I was thinking of a 6x4 or a 6ca4. The 6ca4 uses an amp for the heater, so it will use up too much of my 6.3v supply.
    My experience with Hammond is that the heaters can be higher voltage, if not loaded with their rating. I want the power xfmr working hard, so I don't want to upgrade the iron. Thanks.
    Dan
    Last edited by dcoyle; 08-05-2017, 09:42 PM. Reason: mislabeled 6x4

  • #2
    Any reason you can't use a 5y3 or a 5ar4 on that 5v 2a winding?

    Comment


    • #3
      Personally, I wouldn't hesitate to try it. By the data sheet, a 6ca4 can be run at a minimum of 5.67V. It would come down to how your PT would act under load. I'd measure the 5V winding UNLOADED. And since you'd only be using it at half-load (1A instead of 2) you may get "close enough." More also depends on what kind of current demand you plan on putting on that rectifier. What power tubes are you running?

      Remember that although tubes can be operated SLIGHTLY below spec'd heater voltage and still run safely and with an extended life, that only applies if the current demands placed on them are accordingly reduced, since a lower voltage heater => cooler cathode => less electrons given off => reduced current capacity. So I think that if the rectifier tube is run below its limitations, it could be done... of course, probably would have to ask Hammond or just hold your nose & jump... And I know that manufacturers are usually not keen on advising consumers to use their products "not in accordance with label instructions..."

      So, I guess it depends? As far as why not just use a different 5V rectifier tube, maybe the chassis is already punched for a certain size socket? I personally am not fond of enlarging tube socket or can cap holes, as I have only very simple tools to work with...

      Justin

      BTW: did you mean 6X<5>? The 6X6 is a tuning indicator. And a 6X6 only needs 0.6A of heater current... still too much? And I bet that one would work even better on that 5V winding, IF it can handle the AC voltages and current demands of your power tubes.
      "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 -

      Comment


      • #4
        My bad, 6x4 rectifier is what I meant.

        Mozz, those tubes would be great, but I'm going in a different direction. This amp's theme is that it craps out at low volume, so I want the dynamics of the high source Z rectifier.

        I'm going to run P/P EL90/6005's, a 10 W pentode in a 7 pin socket, but also octal sockets for 6V6's and noval for EL 84's. Each socket pair with its own appropriate value cathode bias resistor. The front is a 12ax7 section, a 6EJ7/EF184 pentode and another AX7 section, going into an AX7 concertina.

        Justin, I'm like you, I think I'll get away with it, I was seeking confirmation. I'm running a 20 ufd cap and then a 1K resistor behind the 6X4, so I'm not too worried about the turn on surge, but I will be drawing max current on occasion.

        Thanks, Dan
        Last edited by dcoyle; 08-05-2017, 05:47 PM.

        Comment


        • #5
          Well, it seems the 6X4 & 6X5 are pretty close in specs, anyway! Heck, if you'll be using all those different sockets for power tubes, why not add an octal and a noval for a 6X5 & a 6CA4 anyway? Just joking on that... But, hey, who's ever used switchable rectifier tubes in an amp before? No, Mesa & Fender don't count here...

          Sounds interesting - oddball tubes! I may see if I have a 6EJ7 handy...

          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 -

          Comment


          • #6
            If you run a heater below it's minimum you cannot expect it to meet the data sheet's maximum current and you did say that you wanted to push it to the max. As lower temperatures the space charge electron cloud surrounding the cathode is reduced so limiting the maximum current you can draw.

            I couldn't figure out which transformer you planned to use from the number H300519. Typical regulation is 10% so your 5V winding will only get you to 5.5V at nominal line voltage i.e you're screwed. Line voltage can be less so now you're screwed again.

            I think using a 5V rectifier is a better choice.
            Experience is something you get, just after you really needed it.

            Comment


            • #7
              So NOW is a good time to bust out the Variac, but instead crank it UP to 140VAC?
              All joking aside, if your regulation facts are right, yeah, go with a 5V rectifier. Is there anything weaker than a 5Y3? I understand Dan may need to think outside "the usual suspects" here...

              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 -

              Comment


              • #8
                if buying and replacing tubes is your thing.... by all means but reliability will be out the window.

                Comment


                • #9
                  Beware of the 6X5, they are known to short out and take out the transformer when using at or near the max rating. Read some antique radio forums for advice on that, they pull them out immediately and replace with solid state when working on some brands. Don't know if the 6X4 has similar horror stories.

                  Comment


                  • #10
                    If you want squishy, then just add series resistance. It lowers the hum and the peak current too. Win win all round. Also add silicon diodes in series with each rectifier plate as its cheap insurance should things go wrong.
                    Experience is something you get, just after you really needed it.

                    Comment


                    • #11
                      I take the point that running the heater low will have the potential for cathode stripping, and thanks for the heads up, but my real question was not about running cold, but will there be enough voltage, since the load is half (1A , instead of 2A at 5V) to run normal, or at least 6.0 V. My experience with Hammond is that they have healthy heater winds.

                      Mozz, thanks for the heads up on the 6X5 characteristics. I have a little Kalamazoo amp that has run it's 6x4 uneventfully for a half century, so that makes me hopeful.

                      I knew the only way to find out is to try, but I thought I might bump into someone here who has tried this kludge before.

                      The 6DJ8/EF184 is widely available, cheap and not as microphonic as the EF86. It is used in the Moonlight amp, but I'm using it with a Ra of 47K, a 200K screen R, a .022 screen bypass cap to cathode, and a 720 ohm Rk.

                      No joke about the two tube sockets for the rectifier. The 6X4 is .6A Htr, 70 mA, 7 pin, the EZ80 is .6A htr, 90 mA, 9 pin, the EZ81/6ca4 is 1 A Htr, 100 mA, 9pin, so there are a series of choices.

                      Thanks nickb, I may well run 47 or 100 ohm resistors on both legs of the 5Y3's output to the first cap, if I can't get the voltage I need on the 5V tap.

                      Dan

                      Comment


                      • #12
                        Originally posted by dcoyle View Post
                        I take the point that running the heater low will have the potential for cathode stripping, and thanks for the heads up, but my real question was not about running cold, but will there be enough voltage, since the load is half (1A , instead of 2A at 5V) to run normal, or at least 6.0 V. My experience with Hammond is that they have healthy heater winds.


                        Dan
                        I answered that for you: no.

                        Post the data sheet for the transformer and we'll know for sure.
                        Experience is something you get, just after you really needed it.

                        Comment


                        • #13
                          i have had the same experience with Hammond heater winds being high.

                          if you have 5.5 VAC you should be fine. those tubes are cheap anyway.

                          DCR for a 5 volt wind is very low, so if you measure 5.5 unloaded, you should have close to that when you plug the tube in as the current will cause a very low voltage drop across the 1 layer wind of #16 wire.

                          Comment


                          • #14
                            Originally posted by dcoyle View Post
                            The 6DJ8/EF184 is widely available, cheap and not as microphonic as the EF86...
                            6EJ7? I'll chalk it up to predictive text & autcorrect...

                            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 -

                            Comment


                            • #15
                              Why not *fully* save on filament consumption, use silicon diodes straight, no glass at all, and add a 20 to 100 ohm series resistor, your choice, to add tube rectifier squishiness.
                              Juan Manuel Fahey

                              Comment

                              Working...
                              X