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constant current issues

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  • constant current issues

    hey guys
    I'm having a problem with my CC rectifier
    it a mastech 20A @30V
    the problem is that I can't get the current over .2 amps
    once I try to rise the amps it goes to .2 and then the volts rise to 36v
    I changed all cables and conections, changed the acid bath changed the tank bar and GP plates
    what else is left
    I'm out of ideas
    is my rectifier dead
    also in CV I rise it to 30V and the amps stay at .2

  • #2
    All of the cheap Chinese lab type power supplies are from the same factory in China, in spite of brand name. These things are adequate for most small scale anodizing purposes (you can't beat the price) but they aren't in the same league as Xantrex (Canadian, and my favorite design) Sorensen (USA) or Agilent (aka HP also USA). The most noticeable thing is the Chinese digital displays won't read below 0.1 Amps.

    First, some of the more common mistakes regarding this. You are aware of course that in order for a current readout (analog or digital) to to actually indicate current you have to actually be drawing current. This means there has to be a load on the power supply to see any indication on the current display. You do have the current control (the knob marked Amps) turned up to maximum (full clockwise) so that it will allow maximum current to flow.
    If you don't have the appropriate power resistor to be the load, hook up an ordinary 120 VAC 150W or larger (larger is better) light bulb to it, polarity doesn't matter. Start at zero volts, you should be able to see the current display increase as you increase the voltage, the light bulb might even glow somewhat. Since we don't know what your anodizing setup is like we will not use it as the load in these tests. If the ammeter (amps display) still shows 0.2 Amps, but the light bulb is glowing (or getting warm) you probably have a defective ammeter in your power supply.