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The Dynaco Tube Audio Forum

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


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    Rebuilding my M125s - can I use this cap in the SCM module?

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    rebellovw


    Posts : 73
    Join date : 2022-01-23

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    Post by rebellovw Tue Mar 22, 2022 4:58 pm

    Where's Waldo?

    Can anyone spot the "problem" with the above amp? Note the amp plays just fine at the moment. Someone just pointed it out on another forum - I'm completely grateful. It should be obvious.

    Thanks!!
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    rebellovw


    Posts : 73
    Join date : 2022-01-23

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    Post by rebellovw Thu Mar 24, 2022 1:30 pm

    The little amp covering for my M125s - I absolutely love it.

    Rebuilding my M125s - can I use this cap in the SCM module? - Page 3 V0LCTSs
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    rebellovw


    Posts : 73
    Join date : 2022-01-23

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    Post by rebellovw Sat Apr 02, 2022 4:39 pm

    We'll my rebuilt amp is back from the Tech and so far so good.  All old bad tubes weeded out.  Bad caps, resistors found and replaced and he talked me into some nicer tube sockets which prevent a tube from being inserted incorrectly.  I wanted to use the Belden but was concerned they wouldn't fit - he was able to get them to work with a nut/spacer.  When I rebuild the other amp - I'll use the Belden tube sockets.

    Rebuilding my M125s - can I use this cap in the SCM module? - Page 3 DPgsx7x

    He also installed the Alex Rubli delay board.  

    I'm now using my bucking transformer which gets the voltage down to 116v.  I tried to use the Weber WS1 (my other thread) but that damn thing is messed up - blows fuses where as the WZ68 and the Mullard work just fine so I'll stick with the Mullard for now.  I've not had good luck with the webers and I'm only running two output tubes.

    Now it is time to begin the rebuild of the sister amp - till then I'll enjoy my Aegir and be in Solid State bliss.

    Note - hum is very slight - with the finished amp - no ground lifts - complete safety a priority- at about high 30's to low 40's dB at the woofer cone/dust cover.  The Aegir is in the 20's.  Anyhow - I can live with it as you only hear it as you stick your head into the woofer - from a seated position it can't be heard.

    Great to have both SS and Tube options.

    Thanks!
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    rebellovw


    Posts : 73
    Join date : 2022-01-23

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    Post by rebellovw Fri Jul 22, 2022 2:58 pm

    I spent some vacation time rebuilding the other amp - now both are completely rebuilt and finally back in service.   I replaced the bloated driver board cap and all new resistors on tube sockets etc.   So far so good - sounds awesome.  I have my Schitt Aegir unplugged at the moment - that is a great amp when these M125s are down.

    Rubli boards doing the job and the bucking transformer is working perfectly for both amps.

    Rebuilding my M125s - can I use this cap in the SCM module? - Page 3 XsfITSc

    Rebuilding my M125s - can I use this cap in the SCM module? - Page 3 3KbAjLd

    Rebuilding my M125s - can I use this cap in the SCM module? - Page 3 BYVfkmk

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    rebellovw


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    Post by rebellovw Sun Sep 04, 2022 1:00 pm

    Shortly after the post above - I dropped off the amp to my tech to have him completely go through it - like the last one to make sure it was good.   He found an issue with some high frequency oscillations so I gave him the contact info for tubes4hifi - and they were awesome - they got back with him right away:

    "Was able to Email them and actually already got a response! Going to try a mod as there
    is some high frequency oscillations at the output of the amp., there is a possible fix
    using some inductors."

    He has now modded both amps with the inductor and confirmed the issue is resolved.

    Thanks tubes4hifi!

    Rebuilding my M125s - can I use this cap in the SCM module? - Page 3 X8i0hco

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    Rec


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    Join date : 2020-03-11

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    Post by Rec Mon Sep 05, 2022 9:06 am

    Hey great info. Question: is this inductor fix the snubber based mod promoted on the ielogical site? Wrap magnet wire around a 47r resistor?
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    rebellovw


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    Post by rebellovw Wed Sep 07, 2022 3:10 pm

    Rec wrote:Hey great info. Question: is this inductor fix the snubber based mod promoted on the ielogical site? Wrap magnet wire around a 47r resistor?

    I'm not sure the specifics - fix was just one inductor. One of these days - I'll open up the amp to see what was done.

    Thanks.

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