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Voltage regulator Motorola Power Supply APN 6003 A. Probably a CB base power supply. I wish to replace the voltage regulator but cannot identify its type and so am unable to tell which pin is which to enable the use of an alternative. Can you help?

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  • formalcolm Sep 27, 2009

    Have been unable to find a circuit diagram.
    Just hoped someone may know so could work out the pin allocation on the original to facilitate finding a replacement.

  • formalcolm Sep 27, 2009

    This power supply has been altered to variable output
    using TO-220 type regulator whose markings are only
    185 213
    I have been unable to identify this component to work out the pin functions as I would like to replace it with an LM388.
    Can anyone identify?

  • formalcolm Feb 06, 2010

    I would also appreciate a copy of the circuit diagram if it is possible to obtain same.

  • formalcolm Feb 06, 2010

    thank you for your respose.
    My problem is sorted as per testimonial in response to Terry2.
    Mine is set up as a variable power supply 0-24V and does give stable voltages according to the Voltmeter and Ammmeter I have mounted on it but the label on the unit only says 8Amp at 13.8V so I have stayed within this current.
    Used mainly for electrolytic de-rusting but also as a power supply for a 12V refrigerator on occasions.
    Have added a fan onto the big heat sink on the rear but not sure this is necessary.
    Would be nice to have circuit diagram in case of future problems.



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Tterry2. Have just found two of these APN6003 power supplies and want to convert one to a varable supply. Would the schematic you found be in an emailable form?


Posted on Feb 06, 2010

  • barbs09 Feb 09, 2010

    Thanks for you reply tterry2. I see what you mean. I might scrap the circuit board and use a LM317 regulator to control the voltage using the existing bridge rectifier, cap and by-pass transistors. It seems like a good transformer though I haven't yet worked out all the taps.




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Are you still trying to fix the APN6003 power supply? I have the schematic. The 9633 is a NPN transistor, not a 3 terminal regulator. Cheers Tim

Posted on Jan 11, 2010

Testimonial: "Spot on thanks. My error in thinking it was a regulator. Mate found the problem was a dry joint in any case but thank you for going to the trouble. "

  • Tim Terry Feb 06, 2010

    Hi Barbs09

    I have a few of these also and had a look at converting the existing control board to variable however it doesnt really lend itself to modification. A much better approach is to simply use a third party regulator board assembly as a driver for the power transistors and power transformer,diode bridge, caps, etc. The original board didnt do a very good job of regulating the output voltage in any case. While it is capable of high current (about 12 amps peak) the voltage vary by more than a volt or so between 0 and 12 amps. The newer variable chip regulators do a far better job and you can buy a pre-assemble unit for less than $20 in Australia from Jaycar Electronics. The circuit I have is on paper and is A3 size! I havent bothered scanning it as I cant see the point in fixing these regulators as the design is too old and inefficient. Anyway I can probably scan it if you really want it. Cheers Tim

  • Tim Terry Feb 09, 2010

    OK I will scan in the schematic for you so you better send me your email address so I can email a PDF to you. Cheers Tim


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One of the most common type is the 3 pin - 1 amp voltage regulators in a TO-220 package, they are the 78xx positive regulators and the 79xx negative regulators. The xx denoted the voltage output of the regulator.
I don't know what type of regulator is used in the APN 6003, if you can obtain a circuit diagram it might help you.

Posted on Sep 27, 2009

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Question, Why do you need to use a voltage regulator?
Are you running on home generator power?
If you run on mains regulated power then replace the voltage regulator with a power surge protection board.
Regards mistyman

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