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


5 posters

    Driver tube flashing! ST-35

    avatar
    hrudu90


    Posts : 27
    Join date : 2011-01-01

    Driver tube flashing! ST-35 Empty Driver tube flashing! ST-35

    Post by hrudu90 Wed May 02, 2012 4:25 pm

    My driver tube on my ST-35 is flashing (only one channel)when turning on!
    The sound is still good as usual!
    Any idea? Time to replace the driver tubes?

    I would appreciate your inputs.

    Thanks

    Bob Latino
    Bob Latino
    Admin


    Posts : 3259
    Join date : 2008-11-26
    Location : Massachusetts

    Driver tube flashing! ST-35 Empty Re: Driver tube flashing! ST-35

    Post by Bob Latino Thu May 03, 2012 4:15 am

    Hi,

    The fact that the tube flashes on start up is probably an indication that that tube is "on the way out" ... You should replace the tube because when it does die it could take out a component (resistor, capacitor etc.) on the driver board for that channel. Personally if it were my ST-35, what I would do is pick up TWO NEW 7247/12DW7 driver tubes and use the one GOOD 7247/12DW7 driver tube you have as a spare.

    Bob
    plexus
    plexus


    Posts : 94
    Join date : 2012-02-17
    Location : Toronto, Canada

    Driver tube flashing! ST-35 Empty Re: Driver tube flashing! ST-35

    Post by plexus Thu May 03, 2012 6:04 am

    Bob's suggestion is a good one. I always have spare tubes around and also a set of "junkers" for testing and burn-in purposes. its a pain because you have to buy the extra tubes and store them but when a tube dies you can instantly replace it instead of waiting for one to be shipped.
    avatar
    scott6058


    Posts : 37
    Join date : 2009-01-21

    Driver tube flashing! ST-35 Empty Re: Driver tube flashing! ST-35

    Post by scott6058 Thu May 03, 2012 7:49 am

    I thought there was a post about the Mullard flash as being normal.
    avatar
    hrudu90


    Posts : 27
    Join date : 2011-01-01

    Driver tube flashing! ST-35 Empty Re: Driver tube flashing! ST-35

    Post by hrudu90 Thu May 03, 2012 12:02 pm

    Thank you, Bob, for your suggestion!
    I did swap the driver tubes and the same tube is now flashing on the other board.
    So it is certainly the tube is 'on the way out'.

    Thank you.
    avatar
    GP49


    Posts : 792
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Driver tube flashing! ST-35 Empty Re: Driver tube flashing! ST-35

    Post by GP49 Thu May 03, 2012 5:21 pm

    But...is it a Mullard? MANY Mullards "flash" brightly at turn on and do so for their whole lives. There may be nothing wrong with the tube.

    I don't know who made the 12DW7s in my dad's old EICO ST-40 but they "flashed" like that the whole time he used it. Still might, but it's been in storage for more than thirty years and I would not want to just plug it in and turn it on!
    Bob Latino
    Bob Latino
    Admin


    Posts : 3259
    Join date : 2008-11-26
    Location : Massachusetts

    Driver tube flashing! ST-35 Empty Re: Driver tube flashing! ST-35

    Post by Bob Latino Fri May 04, 2012 12:25 am

    I guess I read something into the poster's text and thought of the tube "flickering" rather than "flashing" when first turned on. What some of the other's have said is quite true. Mullard 12**7 and other manufacturers who had their small signal 12**7 tubes made by Mullard do exhibit a flashing when first turned on when the tube is cold. If the tube has been on for a period of time and then the amp is shut off and then turned on again while the tube is warm - then the tube WON'T FLASH. If your tube exhibits the symptoms mentioned in the previous sentence, then the tube was most likely made by Mullard and is OK. Sorry for any confusion I may have cause by my post above ...

    Bob

    Sponsored content


    Driver tube flashing! ST-35 Empty Re: Driver tube flashing! ST-35

    Post by Sponsored content


      Current date/time is Thu Mar 28, 2024 12:01 am