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Thread: EB104 amp project

  1. #11
    Orca Whisperer kf0rt's Avatar
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    Very nice job there, OM.

    Reminded me that I needed to rescue a couple of those toroidal transformers that are slated for recycling here at work (NOS). Now safely in the trunk of my car. :)

  2. #12
    Administrator N8YX's Avatar
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    Very nice work. I'm currently walking the swap meet at the Dayton Hamvention and am running into a lot of the things necessary to build such constructs. Be nice to have some decent test gear for the design and test stages and there is no shortage of that stuff here, either.
    "Everyone wants to be an AM Gangsta until it's time to start doing AM Gangsta shit."

  3. #13
    Tribal Elder mw0uzo's Avatar
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    The toroid is a custom wound one. I asked a transformer manufacturer to make something with minimum diameter with worse expected power requirements. My hunch is that the transformer (a 1kva 40v 20a main winding) is even now over-spec'd for what would be required. I reckon you could probably get away with a 800w 40v ac toroid for this purpose.

    edit: a quick calc suggests that what i've got is a 800w continuous toroid, power draw is 1.2kw continuous at rated amp power. i asked for torioid rated at 50% duty cycle at 1.2kw, capable of maintaining a solid 50v supply. The leadouts from the transformer are *very* stout, so it should be perfect....
    Last edited by mw0uzo; 05-18-2012 at 02:17 PM.

  4. #14
    Orca Whisperer kf0rt's Avatar
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    Looks like a really fun project.

    Pulled the datasheet on one of the two different toroids I got and it looks like it's a 1.2kva isolation transformer with two secondaries: one is 1:1 isolation and the other is center-tapped; 93/24 volts (this is spec'd at 110-120 VAC input). Guess that wouldn't be optimal for the MRF150's, but I noticed that the MRF150 is spec'd to 125 volts, so maybe they'd do okay at 93 volts instead of 50? These were used in a high-power servo motor application, and a lot of that stuff is 24/36 volts.

    Just thinking aloud. ;) Odds are slim I'd ever build something like that, but it's fun to think about.

    Is that a readily available PCB you're using, or something you made yourself? I'd be interested in seeing the schematic.

    Hope you'll continue to show the progress here. I love seeing the craftsmanship and your talent is obvious. ;)

  5. #15
    Tribal Elder mw0uzo's Avatar
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    Apparently, the MOSFETs should be rated at 3x the supply voltage, so higher than 60v would probably mean BANG. The eb104 pcb I got from an ebay seller in Greece. There are two of us building these amps at the same time. We got the components and transformers from Communications Concepts in the states. They also sell the PCBs. We just added the (fake) mosfets and heatsinks.

  6. #16
    Tribal Elder mw0uzo's Avatar
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    Any 40v ac, high power toroid would be suitable for this. I was hoping I would find a suitable one in my line of work (audio repair) from a scrap audio amp but one didn't show, so I got a custom one.

  7. #17
    Tribal Elder mw0uzo's Avatar
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    The big challenge is the CPU controller and monitoring circuits really, these are in very early prototype on breadboard at the moment. Next step is to port my beacon code over to the new PIC and get the display working, then get the ADC code and SWR calculations done.

  8. #18
    Orca Whisperer kf0rt's Avatar
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    Good to know (and learning). The last amplifier project I was involved in was based on a 4-400. Have a picture or two here somewhere, but they're black & white. (Really) Mid-1970's. Don't know a thing about the eb104, but it looks really clean.

  9. #19
    Tribal Elder mw0uzo's Avatar
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    Just checked out the 4-400 amplifier.. a tube amplifer. I seriously considered building a tube amplifier, but chickened out at the HV. I've repaired several 100w-200w class tube amps and a few 600w class and always am very cautious of the HV, but knowing how many times i've managed to give myself pretty bad electric shocks over the years I figured it was probably best to stick to 50v...

  10. #20
    Tribal Elder mw0uzo's Avatar
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    eb104 has its problems too though, in its current configuration it doesn't work efficiently above 21mhz. Those capacitors on the output transformer are the problem, they need to be reduced in value to work properly up to 10m

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