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Thread: The Bug is back

  1. #31
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    Got the MCP 71 1R today

    Conrads only do the 2 W and blipping RS will tell you that they keep them but then they don't

    RS is a joke not what it used to be...

    Any way got 100 only one does not want to be out of stock on those

    Burklin seems to be the only source

  2. #32
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    DSCF2239.jpgDSCF2240.jpgDSCF2241.jpg
    Things should take off now at least for the build of the 50 W Paul's F5 Turbo
    Other build has been suspended

    Parcel from Mouser has landed

  3. #33
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    Out put Boards

    I have mounted the thermistor for the temperature compensation as close as possible to the centre pin
    This is the hottest point, that is accessible , of the mosfets

    May be to fast on picking up changes ? comments welcome

    As far as I am concerned, this is the most fiddly part of the build


    DSCF2244.jpgDSCF2249.jpgDSCF2250.jpg

  4. #34
    Bigman80 Guest

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    Quote Originally Posted by Bksabath View Post
    DSCF2239.jpgDSCF2240.jpgDSCF2241.jpg
    Things should take off now at least for the build of the 50 W Paul's F5 Turbo
    Other build has been suspended

    Parcel from Mouser has landed
    Oh dear, suspended a build! Must be bad,

    Looks like a good build anyway, looking forward to seeing the finished article!!

  5. #35
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    Quote Originally Posted by Bigman80 View Post
    Oh dear, suspended a build! Must be bad,

    Looks like a good build anyway, looking forward to seeing the finished article!!
    Hope it is only a delay, I am not that bothered about it, the spare bits I have will surely go in a snip.

    And once Paul's is up and running …

  6. #36
    Join Date: Mar 2010

    Location: Sheffield

    Posts: 2,898
    I'm Simon.

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    I wouldn't turn my nose at an F5t 100w. Even though I've a brace of mod86p amps that need casing up and a preamp with no case...
    Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m

  7. #37
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    things are moving along
    here is how I will clamp the transistors

    Sizes are
    Sink base plate ,this is quite important as heat travels trough this to reach the fins, 13 mm (not 8mm like the Modu sinks )

    drill holes tap M5 depth 10 mm (nice to have a drill whit a stop so one does not drill right trough)
    cooper bar is 20mm X3 mm

    total depth whit transistors from top of bar to hole bottom 17 mm add 2 mm for washers
    Bolts M5 X16

    I like this way to clamp the transistors
    1) pressure is distributed evenly
    2) taightening the screws does not lift the lip of the hole and pushes the transistors up
    3) whit M5 bolts much more pressure can be applied
    Look at the graph in the spec sheet of the Kerafoll 86/82 curve drop whit pressure and stop at 60 Nm

    We are planning on a bias of 2 Amps maybe more at 35 V that will be 70 W for each sink or 35 W on each transistor 140 W idle

    Once set up bias may be increased a fair bit so to get the sinks at a nice 50 C


    DSCF2254.jpg DSCF2253.jpg


    This is the 50 W build
    Meeting tonight as we have to talk about a few things

  8. #38
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    DSCF2249.jpg


    DSCF2244.jpg

    A bit more details about the boards

    The thermistor is fitted to the middle leg of the Mosfets

    this is the hottest accessible point as the leg is welded to the junction where all the up/down up/down happen

    As the temperature go up the mosfets conduct more and the current increase and this increase the temperature

    As the temperature go up the mosfets conduct more and the current increase and this increase the temperature

    As the temperature go up the mosfets conduct more and the current increase and this increase the temperature.....
    Boom

    The thermistor is there to reduce the Bias
    Much more about bias later

  9. #39
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    Well met did not happen not so fuss about it. I carry on regardless
    Input boards are finished



    DSCF2261.jpgDSCF2262.jpg

  10. #40
    Join Date: Mar 2010

    Location: Sheffield

    Posts: 2,898
    I'm Simon.

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    Your progress makes me ashamed, I still have power amps to case up 16 months after I bought them. I ordered cases last week though.
    Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m

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