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  • #16
    Originally posted by nickb View Post
    You can make your own probe for low cost: https://hackaday.io/project/169390-a...erential-probe

    Methinks this is a nice idea. One will be appearing on my bench soon


    That's a nice little project. I just ordered the PCB from OSH Park. 3 boards for $9.85USD, free shipping. I would power it with a battery instead of AC adaptor and no more lugging my isolation transformer onto the bench.

    btw: I have the rest of the schematics for the PF500 if they're needed. I got them at the Loudtech site before they disappeared. The last time I looked at a PF500 I gave up on it and it was trashed. I don't regret it!
    Last edited by dmeek; 11-22-2020, 09:16 PM.

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    • #17
      Originally posted by dmeek View Post
      That's a nice little project. I just ordered the PCB from OSH Park. 3 boards for $9.85USD, free shipping. I would power it with a battery instead of AC adaptor and no more lugging my isolation transformer onto the bench.

      btw: I have the rest of the schematics for the PF500 if they're needed. I got them at the Loudtech site before they disappeared. The last time I looked at a PF500 I gave up on it and it was trashed. I don't regret it!
      I am going to give this PF500 a shot....so far the only component I found gone was one of the output fets.....which are on order along with some of the support components should I need them....
      Cheers

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      • #18
        Generally speaking, if you find a blown output fet, replace the IR20957S driver ic also.

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        • #19
          Originally posted by nickb View Post
          You can make your own probe for low cost: https://hackaday.io/project/169390-a...erential-probe

          Methinks this is a nice idea. One will be appearing on my bench soon
          I'm not getting what SG1 & 2 are ? I'm liking not needing a dual-trace though.
          "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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          • #20
            Originally posted by g1 View Post

            I'm not getting what SG1 & 2 are ?
            Should be spark gaps realized by layout.
            https://hackaday.io/project/169390-a...-probe/details

            - Own Opinions Only -

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            • #21
              Originally posted by dmeek View Post



              That's a nice little project. I just ordered the PCB from OSH Park. 3 boards for $9.85USD, free shipping. I would power it with a battery instead of AC adaptor and no more lugging my isolation transformer onto the bench.

              btw: I have the rest of the schematics for the PF500 if they're needed. I got them at the Loudtech site before they disappeared. The last time I looked at a PF500 I gave up on it and it was trashed. I don't regret it!
              Hope it goes well! Please post the rest of the PF500 as I'd like to see it. Ta!
              Experience is something you get, just after you really needed it.

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              • #22
                I uploaded the PF500 schematics to https://music-electronics-forum.com/...9&d=1606088416

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                • #23
                  Thx dmeek.

                  Here is the power amp from that. If a FET is fried, replace both FETs the 4148 diode, 10 ohm resistor and driver chip. No probes required. A not unusual issue is a shorted output inductor which will blow the FETS due to excessive current. Often they are simple enough you can rewind by hand.

                  Click image for larger version

Name:	Class D Output.JPG
Views:	36
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ID:	918841
                  Experience is something you get, just after you really needed it.

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                  • #24
                    That's not the schematic for the board that I have....the board I have has 4 smt transistors between the gate drive IC and the main output fets......the correct schematic is back in post #12....

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                    • #25
                      Originally posted by dmeek View Post

                      That's a nice little project. I just ordered the PCB from OSH Park. 3 boards for $9.85USD, free shipping. I would power it with a battery instead of AC adaptor and no more lugging my isolation transformer onto the bench.!
                      Populated??

                      wanna sell me one?
                      If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

                      Comment


                      • #26
                        Originally posted by bsco View Post
                        That's not the schematic for the board that I have....the board I have has 4 smt transistors between the gate drive IC and the main output fets......the correct schematic is back in post #12....
                        It's basically the same. In your case replace the driver transistors too. In many ways class D amps are easier to fix than AB.
                        Experience is something you get, just after you really needed it.

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                        • #27
                          I have all the parts ordered.....just waiting for them to arrive....
                          Cheers

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                          • #28
                            Originally posted by SoulFetish View Post

                            Populated??

                            wanna sell me one?
                            Bare boards, All parts are smd. It is designed for 100MHz bandwidth. I might downgrade it to ~10 MHz The opamps I would use are less expensive and draw much less current.

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                            • #29
                              That opamp driving the midpoint drives a heavy capacitive load. I see nothing in the datasheet that says it's not going to hoot like a banshee.
                              Experience is something you get, just after you really needed it.

                              Comment


                              • #30
                                Originally posted by dmeek View Post

                                Bare boards, All parts are smd. It is designed for 100MHz bandwidth. I might downgrade it to ~10 MHz The opamps I would use are less expensive and draw much less current.
                                The board may have a bandwidth of 100MHz, but it would be difficult to compensate the whole array I would think. wouldn't changing the proximity of the 2 EZ mini-hook leads to one another alter the capacitance enough to cause HF errors?

                                I'm not set up to populate a smd board, you guys ever use a PCB manufacturer to fabricate and populate PCBs for you? what kind of minimum quantity and cost would that entail?
                                If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

                                Comment

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