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

    Power Supply Delay Action Board for MKIII amp

    Share

    tubemania

    Posts: 3
    Join date: 2011-09-01

    Power Supply Delay Action Board for MKIII amp

    Post by tubemania on Thu Sep 01, 2011 1:29 am

    Hi All,

    I'm new to the forum and is also a bonafide noob to tube audio. I'm putting together a dynakit/triode MKIII kit with the Poseidon driver board and SDS Lab capacitor kit. I have no trouble following the instruction until I got fancy and bought a power supply delay action board on ebay made by Sophia Electric. Here is the introduction and instruction for the delay:

    This board was designed by Sophia Electric for its service department to retrofit into tube amps made earlier. It would permit dynaco or any other brands of tube amplifier to warm up vacuum tube filament first, then switch to high plate voltage in about 12 - 30 seconds later. Research shows that without proper warm up, vacuum tubes would decrease life span significantly (instead of 5-7 years of normal life span in average home use, power tubes would wear out within 1-2 years in most situations). That is the reason why most tube amp makers would only offer 6 month warranty on tubes.

    Braid green wires are for 6.3V AC (from tube filament supply).
    Red/Black wires (2 pairs) are being used to switch up to two (2) sets of power supply.


    I figured I should use Pins 2 & 7 of either V1 or V2 for the 6.3V AC supply. What I'm not sure of is how to hook up the delay (relay) to switch the plate power supply. Do I put the relay (Red/Black wires) between the output transformer's Blue wire and V2 Pin 3, and Blue/White wire and V1 Pin 3? I'd appreciate any help you guys can give me. Thanks.

    tubes4hifi
    Admin

    Posts: 998
    Join date: 2008-11-30

    Re: Power Supply Delay Action Board for MKIII amp

    Post by tubes4hifi on Sat Sep 03, 2011 3:42 pm

    Hi Tubemania, welcome
    I hope that you did not try what you suggested!!
    The two pairs of red/black wires on the relay need to be connected in series with the red power leads on the transformer.
    So you disconnect the red wires from the tube rectifier (GZ34) and connect them to the relay, the return wires back to pins 4 and 6 on the rectifier tube. The relay will connect the HV to the rectifier tube after its timing delay. see wiring diagram below:


    tubemania

    Posts: 3
    Join date: 2011-09-01

    Re: Power Supply Delay Action Board for MKIII amp

    Post by tubemania on Sun Sep 04, 2011 4:22 am

    Thank you very much tubes4hifi. You just saved my MKIII! After waiting and no responses, I hooked it up the way i knew how. Good thing I haven't fired it up yet (no doubt it would have been a spectacular fire) because i'm still looking for a 400V DC DPDT switch to do the triode/pentode switching from Bob Latino's post. I also asked the ebay seller for help, but he hasn't reply. I guess i'm worth his time only during the sale. Thank Goodness for people like you. The diagram is extremely helpful.


    tubes4hifi
    Admin

    Posts: 998
    Join date: 2008-11-30

    Re: Power Supply Delay Action Board for MKIII amp

    Post by tubes4hifi on Mon Sep 05, 2011 3:47 pm

    I've got the triode-pentode switching kits on my webpage about half-way down . . .
    http://tubes4hifi.com/ST70.htm

    tubemania

    Posts: 3
    Join date: 2011-09-01

    Re: Power Supply Delay Action Board for MKIII amp

    Post by tubemania on Thu Sep 08, 2011 3:28 am


    Thanks for the info tubes4hifi. I finally found a switch that I think will work.

      Current date/time is Fri Oct 31, 2014 10:24 pm