The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    PAS-3 I replaced the selector switch and messed something else up.

    Share

    JohnM24018

    Posts : 3
    Join date : 2018-03-28

    PAS-3 I replaced the selector switch and messed something else up.

    Post by JohnM24018 on Tue Aug 14, 2018 9:55 am

    I replaced the selector switch on my PAS-3. I measured the voltage on the tube socket pins when I thought I was done and found pin 1 & 6 on all 4 tubes to have 479 & 497 volts. I have a SDS Capacitor Board with solid state diodes that has been working fine but the installed board has the capacitors underneath and inaccessible. The preamp sat over night, unplugged and the charge has dropped to just over 250 volts. The voltages were taken with the tubes not installed. There was no input to the preamp and the preamp was not hooked up to the power amp. I would sort of like to drain off the stored power. I have previously hooked up a 1K resistor with an alligator clip.
    1. Will touching the hot pins accomplish the discharge properly?
    2. Will that discharge everything I should be concerned about?
    3. Any insight on the high voltage would be helpful.
    The problem is certainly not with the switch installation. I must have unhooked and re-hooked something up wrong during the install.
    Thanks. John.
    avatar
    Peter W.

    Posts : 888
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: PAS-3 I replaced the selector switch and messed something else up.

    Post by Peter W. on Tue Aug 14, 2018 12:03 pm

    JohnM24018 wrote:I replaced the selector switch on my PAS-3. I measured the voltage on the tube socket pins when I thought I was done and found pin 1 & 6 on all 4 tubes to have 479 & 497 volts. I have a SDS Capacitor Board with solid state diodes that has been working fine but the installed board has the capacitors underneath and inaccessible. The preamp sat over night, unplugged and the charge has dropped to just over 250 volts. The voltages were taken with the tubes not installed. There was no input to the preamp and the preamp was not hooked up to the power amp. I would sort of like to drain off the stored power. I have previously hooked up a 1K resistor with an alligator clip.
        1. Will touching the hot pins accomplish the discharge properly?
        2. Will that discharge everything I should be concerned about?
        3. Any insight on the high voltage would be helpful.
    The problem is certainly not with the switch installation. I must have unhooked and re-hooked something up wrong during the install.
    Thanks. John.

    First, the most common form of "mess" made when doing this sort of repair/upgrade is a solder-bridge.
    Second, is a cold-solder.
    Third is a transposed wire.

    So:

    a) Put the unit aside for 24 hours. This erases any visual memory you have - and allows you to look at the issue(s) with fresh eyes. Really.
    b) Go over each step, in sequence, of what you did, from the beginning.
    c) Follow to the end, even if you find the (a) problem midway.

    Betcha you figure it out!

    Good luck with it!
    avatar
    j beede

    Posts : 466
    Join date : 2011-02-07
    Location : California

    Re: PAS-3 I replaced the selector switch and messed something else up.

    Post by j beede on Tue Aug 14, 2018 3:27 pm

    Did you randomly reflow messy/ugly/dull solder joints as you went along? If not then you may want to double (triple) check the connectivity related to fresh(er) looking solder joints.

    Sponsored content

    Re: PAS-3 I replaced the selector switch and messed something else up.

    Post by Sponsored content


      Current date/time is Mon Sep 24, 2018 4:33 am