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


    Things to look for when a tube blows?

    Share

    polarflux

    Posts : 40
    Join date : 2010-02-12

    Things to look for when a tube blows?

    Post by polarflux on Thu Jan 30, 2014 7:52 pm

    Blew a power tube in my amp last night and was in the process of ordering another set when the dealer became concerned about the short lifespan I got from my current tubes. So, before I pull the trigger on a new set, what are some of the things I should look for to ensure that the failure was not simply due to a worn out tube? Noticed a bit of AC hum in the left channel before the tube went as well (same channel where the tube died).

    Jim McShane

    Posts : 154
    Join date : 2011-10-19
    Location : South Suburban Chicago

    Re: Things to look for when a tube blows?

    Post by Jim McShane on Thu Jan 30, 2014 8:52 pm

    polarflux wrote:Blew a power tube in my amp last night and was in the process of ordering another set when the dealer became concerned about the short lifespan I got from my current tubes.  So, before I pull the trigger on a new set, what are some of the things I should look for to ensure that the failure was not simply due to a worn out tube?  Noticed a bit of AC hum in the left channel before the tube went as well (same channel where the tube died).

    The tube may have been on the way out for some time. The hum could well have been from the really bad AC balance that would result from one tube being real weak while the other in that channel was fine. The farther out of AC balance an amp is, the less hum cancellation occurs.

    arledgsc

    Posts : 340
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: Things to look for when a tube blows?

    Post by arledgsc on Fri Jan 31, 2014 11:01 am

    Not sure what amp you have but on the Bob L. amps check the 10 ohm 2W power tube cathode resistors. I lost a power tube recently and smoked the resistor. It measured OK but smelled burnt. Also a good time to check all solder connections. And with an ohmmeter check the resistance of the output transformer primary. A good tool is just compare readings from the working channel against the suspect. Of course drain the caps first before probing. Not much else except perhaps a bad coupling cap. Assuming, of course, if there is an issue it is confined to the power section.

    zx

    Posts : 194
    Join date : 2011-08-05

    Re: Things to look for when a tube blows?

    Post by zx on Fri Jan 31, 2014 11:58 am

    What is the B+ on the output tubes plate.......over 500V??.........
    ....i have 6ea Dynaco MK3s an....
    have lost no output tubes in years....
    I run my B+ at 460-80.............good luck


    Thanks for the site Bob..............

    Sponsored content

    Re: Things to look for when a tube blows?

    Post by Sponsored content Today at 6:13 pm


      Current date/time is Wed Dec 07, 2016 6:13 pm