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Posts posted by halen

  1. You can look up the spec's for those old opamps to see if they will fail with a supply voltage from this project that is higher than the max voltage allowed for them.
    The OP37 and NE5534 are de-compensated and therefore would oscillate in this circuit.

    Since you cannot get modern parts then use a transformer with a lower voltage like 20VAC which would give a unregulated positive supply to the opamps of 29VDC without a load, plus the negative supply of 5.6VDC so they will have a total supply of 34.6V which is less than the 36V max allowed for ordinary opamps.
    The project will then have a max output voltage at 3A of current of only about 20VDC.

    EDIT: I find UA741 OP Amp, it is 44V, its not decompensated....

    Ok I try it with some 44V OPAmp.  I can buy OPA445 now, but for $14.11 per unit :-D Its wery expensive, so its better to buy professional lab power supply.

  2. It is too bad that you can't get stuff in your country.

    I just order parts from a neighbor country (USA) online and they are delivered to me the next morning.

    I can buy: LF356N, OP37, OP07, NE5534. It is possible to use one ot those?

    EDIT: I can buy OPA604 - 48V supply voltage

  3. Where are you where common parts are not available?

    Come over to this part of the world where everything is available.

    Czech Republic - Europe, Alll distributors of electronics parts doesnt have OPA445, and if I want to buy them, i  must buy 100+ pieces... :-( Iam not crazy.

  4. The old LM143 and SG143 are very slow and their output voltage swing is limited. Their offset voltage adjustment is different. The circuit would need many changes for them to be used.

    Thank you for super-quick answer! So what now? I find next Ha7-2645-5 OP, but best is OPA445 isnt it?

  5. Multisim might not understand how the negative 5.6V supply works.

    I replaced TLE2141CP with OPA445 (I try many others OP amp but 100% work only OPA445) and replace 24VAC TR with 30VAC to get max voltage 30V and now, in simulation PSU work. Both V and I regulation work perfect.  But I have next problem. If I measure output with osciloscope I get 20kHz oscilating about 200mV AC. Where can be problem? If I replace output 10uF capacitator with 100uF, oscilating is now pretty low in uV. But this is not right way.... Can somebody help please?
  6. Hello

    Iam new there. I have problem with this PSU. I designed it in the Multisim simulation, but doesn't work. Used modified partlist, 24VAC TR, BZX83C5V6, I have troubles with - 5.6V D7. I using TLE2141CP OP amps in simulation and if I connect U2 to the -5.6V, then voltage drop to 800mV. If I connect U2 pin 4 to GND, then PSU work, but LED slow flashing :-D. It seems that RV1 don't work. It is possible to test this PSU in simulation or PSU in simulation don't work? I mean that it must work. I have 100% correct wiring and parts. Please help.

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