The Dynaco Tube Audio Forum

Would you like to react to this message? Create an account in a few clicks or log in to continue.
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


4 posters

    Rectifier and blown fuse

    jimmeq
    jimmeq
    jimmeq


    Posts : 60
    Join date : 2017-02-24
    Location : Six Miles West of Jiminy Peak Ski Resort
    • Post n°1

    Rectifier and blown fuse Empty Rectifier and blown fuse

    Post by jimmeq Sat Mar 14, 2020 7:45 am

    When a rectifier goes south, does the fuse usually blow too?


    Here's why I ask:

    Upon powering on my ST-120, I heard a slight crackle and the rectifier arced. The fuse was blown as well. I replaced the tube and fuse and again saw the rectifier arcing then the fuse blew. (It was not a known good rectifier used to replace the first one.)

    I re-flowed the solder on the cap*, replaced the fuse and inserted a new Sino 5AR4. The amp works fine now. Typical voltage at my house is 117 - 120V.


    * I had replaced this several months ago and it being the most recent change, thought it might be the problem.
    • Back to top
    peterh
    peterh
    peterh


    Posts : 1833
    Join date : 2012-12-25
    Location : gothenburg, sweden
    • Post n°2

    Rectifier and blown fuse Empty Re: Rectifier and blown fuse

    Post by peterh Sat Mar 14, 2020 8:05 am

    jimmeq wrote:When a rectifier goes south, does the fuse usually blow too?


    Here's why I ask:

    Upon powering on my ST-120, I heard a slight crackle and the rectifier arced. The fuse was blown as well. I replaced the tube and fuse and again saw the rectifier arcing then the fuse blew. (It was not a known good rectifier used to replace the first one.)

    I re-flowed the solder on the cap*, replaced the fuse and inserted a new Sino 5AR4. The amp works fine now. Typical voltage at my house is 117 - 120V.


    * I had replaced this several months ago and it being the most recent change, thought it might be the problem.
    The 5AR4 in VTA-120 and to a less extent VTA-70 is working hard.

    A rectifier that has arched is consumed and should be junked.

    The yellow sheet mod seems to make rectifiers last longer as flash-over will not
    lead to destruction. Recommended !
    • Back to top
    jimmeq
    jimmeq
    jimmeq


    Posts : 60
    Join date : 2017-02-24
    Location : Six Miles West of Jiminy Peak Ski Resort
    • Post n°3

    Rectifier and blown fuse Empty Re: Rectifier and blown fuse

    Post by jimmeq Tue Mar 17, 2020 7:04 am

    Thanks Peterh. I guess it's somewhat of a rhetorical question because it happened twice but I'm a tube amp beginner. I'm just curious about the fuse blowing when a rectifier goes south. I'll increase my fuse stock. I plan to upgrade to a Tung-Sol  5AR4 and keep the Sino as a spare.

    I do have a SS but just love the look of a tube rectifier. (I did do a search in the Basket but did not find any info on fuses blowing when a rectifier arc's.)


    *I'd have responded sooner but I had to get skiing before all the ski areas shut down because of covid-19.
    • Back to top
    peterh
    peterh
    peterh


    Posts : 1833
    Join date : 2012-12-25
    Location : gothenburg, sweden
    • Post n°4

    Rectifier and blown fuse Empty Re: Rectifier and blown fuse

    Post by peterh Tue Mar 17, 2020 9:33 am

    jimmeq wrote:Thanks Peterh. I guess it's somewhat of a rhetorical question because it happened twice but I'm a tube amp beginner. I'm just curious about the fuse blowing when a rectifier goes south. I'll increase my fuse stock. I plan to upgrade to a Tung-Sol  5AR4 and keep the Sino as a spare.

    I do have a SS but just love the look of a tube rectifier. (I did do a search in the Basket but did not find any info on fuses blowing when a rectifier arc's.)


    *I'd have responded sooner but I had to get skiing before all the ski areas shut down because of covid-19.

    Do install the "yellow sheet mod" where a pair of 1n4007 or un4007 is connected in series
    with the 5ar4 anodes. This prevents huge currents if the tube flashes thereby saving
    fuse and tube.

    • Back to top
    Mangaman80
    avatar
    Mangaman80


    Posts : 2
    Join date : 2017-03-01
    • Post n°5

    Rectifier and blown fuse Empty Re: Rectifier and blown fuse

    Post by Mangaman80 Tue Mar 17, 2020 11:09 am

    What’s the yellow sheet mod? I have the 120 and haven’t been on the forum in a while? I had rectifier issues early on but that has since slowed and I haven’t changed my rectifier out in a long time.

    Thanks!
    Mark
    • Back to top
    Bob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3262
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°6

    Rectifier and blown fuse Empty Re: Rectifier and blown fuse

    Post by Bob Latino Tue Mar 17, 2020 11:27 am

    Mangaman80 wrote:What’s the yellow sheet mod? I have the 120 and haven’t been on the forum in a while? I had rectifier issues early on but that has since slowed and I haven’t changed my rectifier out in a long time.

    Thanks!
    Mark

    Check the link below ..

    Tube rectifier yellow sheet diode mod

    Bob
    • Back to top
    Sponsored content

    Sponsored content


    • Post n°7

    Rectifier and blown fuse Empty Re: Rectifier and blown fuse

    Post by Sponsored content

    • Back to top
      Current date/time is Fri Apr 26, 2024 2:54 pm