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  1. #21
    Join Date
    Jun 2007
    Posts
    3757
    I have a spare board here. When I get time test then I will post a solution.
    Might put it on my surface grinder. Will be better than the VFD at low speeds.
    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.

  2. #22
    Join Date
    May 2005
    Posts
    925
    Thanks Neil!


    Pablo
    ● Distribuidor Syil en Argentina ● "www.syil.com.ar" ●

  3. #23
    Join Date
    May 2005
    Posts
    925
    Neil, Im looking at SX3 schematics and AN1101 pdf, it appears that MC33035 needs a pot with wiper on pin 11 which goes thru a diode directly to pin 4 (E6V) to adjust speed but you suggested to use this pin as the top pin of the pot.
    I don't have a deep understanding of how it works, so I may be writing nonsense


    Pablo
    ● Distribuidor Syil en Argentina ● "www.syil.com.ar" ●

  4. #24
    Join Date
    Jun 2007
    Posts
    3757

    Exclamation

    Pablo,

    If you have an IC socket on the board, I would suggest implementing as per figure 3 in AN1321. It is closest to what you have and has the MC33039.
    I am only guessing it is MC33035/39 but there are too many pins matching for it to be anything else, and I have used that chip extensively.
    It is closest to what you have, and I haven't traced out the board, (not my doing that SX3 diagram).
    I really can't see how it works properly with pin 10 not connected and why they used external PWM, and I am almost certain something connects to pin 11 from the stupid TL491 circuit. Without the internal PWM the current limit won't work properly.
    When it overloads at present, it just shuts down instantly, somehow. Not sure how it kills itself on overload.
    Their attempt at implementing soft start failed miserably, and they kept adding stuff. Or something to do with isolating the front panel (which they didn't!!) introducing spikes.
    First, try to get it running with the push button board, then measure some signals with a meter, remembering all the circuits are hot.

    Implementing the circuit in AN1321 will work perfectly, but you need to adapt it to the motor characteristics and run it on a low voltage current limited bench supply (40v 1-2A) during testing or you will end up with smoke. 40v direct to capacitors E1,E2.
    You still need to supply the TNy268, so it gets really messy, and it is needed for the high side drive supplies for the IGBTS.

    Simplest really is disconnect AC from BR1 and supply it with a variac with a 100 or 250w light bulb in series with output.
    You still need normal AC supply for BR2.
    And if you don't have an isolating transformer, just don't do it.
    With care..

    revision. circuit. Junction or R12 (10K) and C8 go to pin 10. It is making more sense now.
    Pin 11 goes to the junction of Q2-e and D14-A.
    Still not sure what the TL494 does!! Needs more circuit tracing. It might be detecting overload, and then it kills the reference. Some lines still missing.
    Speed input signal is DC voltage a SV1 pin 6, 0-5v. The missing lines to TL494 will be why it is not working (yet)
    Carefully measure all supplies with a multimeter (across the regulators is best).
    Don't probe it. Connect wire to meter first, then apply power for each test. Too many horrible voltages on nearby tracks.

    You must enable the JK2 relay with a 3K3 from SV1-pin 5 to SV1-pin 2. Pin 9 on SV1 is an output (pulses to front panel speed display)
    On CN2, K3 and K4 must be bridged to turn on power relay.
    P2 input (SV1 pin 6) is speed control input ARM of 10K POT. Top of pot to PIN 4 (E6V). Bottom of pot to PIN 3(EGN)
    DO NOT CONNECT anything to PIN 1 or 2 of SV1, relative to any other wiring. It is 5v relative to frame ground, and TL494 circuit is still not quite right.
    I haven't checked yet, but I suspect the connection to pin 15 of TL494 is not as drawn. If it was there would be smoke!!
    Attached Files Attached Files
    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.

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