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  • #31
    Originally posted by TarheelTechinTraining View Post
    I'm sorry for being such a newbie, Juan. Short and long, I'm using the PT and OT from a jtm60 in a jcm800.
    Understood, but we need to know what sort of rectifier arrangement you came up with. A schematic would be most helpful. Since you have no HT CT, you must have done something different. The schematic doesn't have to be anything fancy. Just draw up your PS as you have it and upload it. It's nearly impossible to help you without knowing what circuit you are working with.
    "Yeah, well, you know, that's just, like, your opinion, man."

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    • #32
      Click image for larger version

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ID:	837225 I hope this is right

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      • #33
        ......and that bridge rectifier/cap circuit is hooked to the 380V tap of the transformer each end of winding to an AC input of the bridge (where the little squigglies are )?

        We also need to know how your primary is wired. You have two windings. are they series, parallel, other. Can you draw how you have the primary configured?
        "Yeah, well, you know, that's just, like, your opinion, man."

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        • #34
          Click image for larger version

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ID:	837226Click image for larger version

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ID:	837226 that's l[ATTACH=CONFIG]33380[/ATTACH line voltage and neutral

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          • #35
            This may be some helpful reading. At any rate, it looks like you've got the HT part working, albeit pretty high voltage.

            http://www.hammondmfg.com/pdf/5c007.pdf
            "Yeah, well, you know, that's just, like, your opinion, man."

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            • #36
              Thanks, Dude. How can I tame the B+ voltage?

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              • #37
                Click image for larger version

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ID:	837233 is this right for the bias ?

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                • #38
                  I'm a little confused about how this happened at all when the rectifier type/voltage confusions/center taps/transformer specifics/request for actual schematics/etc. has already been covered in the other thread about this project. Same problems, same answers, new thread inside of a week?

                  I'm glad it's working. Circuit and voltages seem correct now. The JTM60's have a VP of 480+. You'll need sturdy tubes. Especially if you plan to drive them into clipping.
                  "Take two placebos, works twice as well." Enzo

                  "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                  "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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                  • #39
                    Sorry for the rehash. I felt I had posted in the wrong place. Plus I finally understood what I very was missing, grounding the bridge.

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                    • #40
                      Originally posted by TarheelTechinTraining View Post
                      [ATTACH=CONFIG]33387[/ATTACH] is this right for the bias ?
                      No, No, No!
                      WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
                      REMEMBER: Everybody knows that smokin' ain't allowed in school !

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                      • #41
                        Originally posted by TarheelTechinTraining View Post
                        [ATTACH=CONFIG]33387[/ATTACH] is this right for the bias ?
                        We can demonstrate how to implement the bridge for this circuit, but even then you may not get the bias voltage you need from the 43V winding. You'll probably need to use a voltage doubler rectification.
                        "Take two placebos, works twice as well." Enzo

                        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                        "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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                        • #42
                          Do not wire up the circuit you posted.

                          A little simulating and it looks like you could get about -39v to -53V from the bridge circuit if you do it like this instead:
                          Attached Files
                          "Take two placebos, works twice as well." Enzo

                          "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                          "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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                          • #43
                            Originally posted by Chuck H View Post
                            You'll probably need to use a voltage doubler rectification.
                            If you look at the jtm600 diagram, you'll see this is the case. If there were a better option, I think they would have used it.
                            "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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                            • #44
                              Originally posted by g1 View Post
                              If you look at the jtm600 diagram, you'll see this is the case. If there were a better option, I think they would have used it.
                              One observation is that the JTM600 circuit seems to be regulated to 51V with a zener. I think the bridge circuit I posted above would actually provide just as much if not a tad more. Maybe not a bad thing with modern tubes. I'm using a pair of Ruby EL34B's and IIRC the bias is something like -47V with 470Vp. Considering the component count and difficulty of either circuit I think the bridge option might be easier too. Then again, I made up the circuit above and the one originally used with that PT is tried and proven. Not that I have any doubts about my circuit

                              EDIT: Looking at the JTM600 circuit again, it doesn't look like a voltage doubler to me.?. It looks rather like a complicated cousin of the one I posted.
                              Last edited by Chuck H; 03-28-2015, 09:08 PM.
                              "Take two placebos, works twice as well." Enzo

                              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                              "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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                              • #45
                                I've implemented the changes to my bias, thanks to Chuck.Though I can only get -56 to -42 for bias.

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