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    Reuse or replace C354 choke?

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    Donkeyshins

    Posts : 19
    Join date : 2011-07-18

    Reuse or replace C354 choke?

    Post by Donkeyshins on Wed May 08, 2013 2:09 pm

    I just acquired a time-capsule Stereo-70 (factory built - still has original tubes even!) that I'm going to rebuild / upgrade. One thing I noticed when I took the bottom cover off the chassis is that the C354 choke has dripped a bit of wax. I happen to have a spare C354 choke from Triode in my parts bin - should I replace the choke or simply reuse the existing during the rebuild? The PS is going to remain more-or-less stock (albeit with UF4007 diode in place of the selenium rectifier, new bias electrolytics and an 80/30/20/20uF twist-lock PS cap). I'm still mulling the options for the driver board (trying to decide between the VTA and DIYTube board).

    Thanks,

    -D

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Reuse or replace C354 choke?

    Post by Bob Latino on Wed May 08, 2013 2:35 pm

    Replace the choke with the Triode version. It is a better choke than the original Dynaco C-354 choke and won't leak that brown goo.

    As to the DIYtube ST-70 board vs. the VTA driver board. The DIYTube board (AFAIK) is only sold as a board which means they give you a parts list when you buy the board and you have to source the parts on your own. With the VTA driver board you may EITHER buy the board alone or purchase your VTA driver board with a complete parts set. The DIYtube board also uses (AFAIK) at least in part the original Dynaco wirewound bias pots. The VTA has its own "on board" bias system and does not use any part of the original Dynaco bias system.

    Other than that, the circuits of both boards are similar. The DIYtube board uses a 12AX7 voltage amplifier tube and two 12AU7 phase splitter/inverter tubes while the VTA driver board uses three 12AU7 type tubes for both voltage amplification and phase splitter/inversion.

    Bob


    Donkeyshins

    Posts : 19
    Join date : 2011-07-18

    Re: Reuse or replace C354 choke?

    Post by Donkeyshins on Wed May 08, 2013 2:43 pm

    Bob Latino wrote:Replace the choke with the Triode version. It is a better choke than the original Dynaco C-354 choke and won't leak that brown goo.

    As to the DIYtube ST-70 board vs. the VTA driver board. The DIYTube board (AFAIK) is only sold as a board which means they give you a parts list when you buy the board and you have to source the parts on your own. With the VTA driver board you may EITHER buy the board alone or purchase your VTA driver board with a complete parts set. The DIYtube board also uses (AFAIK) at least in part the original Dynaco wirewound bias pots. The VTA has its own "on board" bias system and does not use any part of the original Dynaco bias system.

    Other than that, the circuits of both boards are similar. The DIYtube board uses a 12AX7 voltage amplifier tube and two 12AU7 phase splitter/inverter tubes while the VTA driver board uses three 12AU7 type tubes for both voltage amplification and phase splitter/inversion.

    Bob


    Thanks, Bob. I already have some of the parts for the DIYTube board (PIO coupling caps, smooth-plate Telefunken 12AX7 voltage amplifier) which is, in part biasing (no pun intended) my decision.

    -D

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: Reuse or replace C354 choke?

    Post by tubes4hifi on Wed May 08, 2013 4:44 pm

    also if it's an original Dynaco from the 60s the output tubes are likely Mullards labeled Dynaco, they say, "made in Great Britain"
    and are worth alot of $$$ Very Happy same with the rectifier tube - I just saw a Mullard 5AR4 in a Dynaco last week,
    I've also got one in an original Heathkit amp.

    Donkeyshins

    Posts : 19
    Join date : 2011-07-18

    Re: Reuse or replace C354 choke?

    Post by Donkeyshins on Wed May 08, 2013 5:21 pm

    tubes4hifi wrote:also if it's an original Dynaco from the 60s the output tubes are likely Mullards labeled Dynaco, they say, "made in Great Britain"
    and are worth alot of $$$ Very Happy same with the rectifier tube - I just saw a Mullard 5AR4 in a Dynaco last week,
    I've also got one in an original Heathkit amp.

    The EL34s are RCA-badged Mullards and the rectifier is also a Mullard. You can have them when you pry them out of my cold, dead hands. Wink

    -D

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