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    Restoring Heavily Modded PAS 2 so it can be used

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    DarthBubba

    Posts : 81
    Join date : 2012-05-05

    Re: Restoring Heavily Modded PAS 2 so it can be used

    Post by DarthBubba on Tue Apr 09, 2013 1:48 pm

    thinker1920 wrote:I'm still surprised that PC 5 is suppose to be fed 330 volts seems high.

    What are the DC Volts readings for eyelet 16 on both boards?

    thinker1920

    Posts : 22
    Join date : 2013-04-04
    Age : 28
    Location : Binghamton, NY

    Re: Restoring Heavily Modded PAS 2 so it can be used

    Post by thinker1920 on Tue Apr 09, 2013 2:16 pm

    currently with the wrong resistor values, 317 for PC 5 and 316 for PC 6, I'm going to the electronics store soon to get the right resistor values.

    DarthBubba

    Posts : 81
    Join date : 2012-05-05

    Re: Restoring Heavily Modded PAS 2 so it can be used

    Post by DarthBubba on Tue Apr 09, 2013 3:50 pm

    thinker1920 wrote:I'm still surprised that PC 5 is suppose to be fed 330 volts seems high.

    The published "Absolute Maximum" voltage is 300v on the 12AX7 plates, 100 to 250VDC is the design "Center Value." The PAS 2 & 3 run the PC5 plates at 175 & 200 volts, well within the safe range. Gotta count the voltage drop across the plate resistors.

    thinker1920

    Posts : 22
    Join date : 2013-04-04
    Age : 28
    Location : Binghamton, NY

    Re: Restoring Heavily Modded PAS 2 so it can be used

    Post by thinker1920 on Wed Jul 24, 2013 8:35 pm

    So I never can get my voltages spot on and it really bugs me Razz

    It's suppose to be 405 -> 355 -> 330 -> 210

    I'm getting 402.5 -> 343 -> 312 -> 220

    and besides the resistor I had to put after the diodes all the other resistors are the exact values that the originals were 10K 10K and 47K

    What the heck's going on? and is this enough of a difference to cause a problem or is it close enough?

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: Restoring Heavily Modded PAS 2 so it can be used

    Post by tubes4hifi on Thu Jul 25, 2013 12:20 pm

    thinker,
    your voltages are right on!! don't overthink it !
    Any tube amp or preamp has voltage variations of 5-10%
    Your worst voltage is 5% off!

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