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Portaflex solid-state recto

Discussion in 'Amps [BG]' started by Precisionb87, Dec 8, 2012.

  1. Precisionb87

    Precisionb87

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    Hi Everyone.
    I have a '68 portaflex B-15-N-F that I want to make solid state rectified. I am experienced with electronics, and fully realize the precautions that need to be taken around vintage amps and their potentially lethal plate voltages.

    Anyhow, I plan on salvaging the octal base from a used-up tube, and implementing a simple diode array with a power resistor in series to replicate the 50 volt drop across a conventional tube recto. Thus a plug-and-play replacement. (much like what Weber sells, but at a much lower cost:))

    My question: Has anybody figured out what value resistor to use?

    Being experienced with electronics, I know how to figure it out (by taking desired voltage drop in this case 50v, and dividing it by the measured operating current) (Ohm's Law) BUT if somebody has already done this, it would save me the time of taking the current measurement.
  2. coreyfyfe

    coreyfyfe Supporting Member

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  3. Steve Dallman

    Steve Dallman Supporting Member

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    Weber Copper Caps would be the ideal replacement, offering whatever voltage drop you want, and soft start. Inside are the usual diodes, the correct resistance for whatever voltage drop you desire, and a thermistor to bring the voltage up slowly. I have them in several amps, and have opened a couple to see what was inside.

    http://www.webervst.com/ccap.html
  4. Precisionb87

    Precisionb87

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    I was unaware that tubeandmore sold them. They don't have the soft start, but the portaflex has a standby switch, so I don't really need that. They are considerably cheaper than Webers. I'll go with that then. Thanks for the help guys.

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