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    VTA ST-70 rectifier issues - solved !

    Brap
    Brap

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    VTA ST-70 rectifier issues - solved ! Empty VTA ST-70 rectifier issues - solved !

    Post by Brap on Sat Feb 23, 2019 1:54 pm

    Rectifier arced last week when I got home after bringing the amp in to a local shop to audition speakers. Fuse blew, replaced that and the tube, all good after that. Last night fuse blew again. Rectifier check out OK at local shop on their tube tester. Did the "yellow sheet" mod this morning and getting another rectifier ( non JJ) and will try again.  Interestingly enough was driving some Paradigm Studio V10 listening to Ray Brown both times this happened. (great low bass)  Maybe the quad cap is reaching it's useable life?  Amp build was 7 years ago. Thoughts appreciated.
    peterh
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    Post by peterh on Sat Feb 23, 2019 2:23 pm

    Brap wrote:Rectifier arced last week when I got home after bringing the amp in to a local shop to audition speakers. Fuse blew, replaced that and the tube, all good after that. Last night fuse blew again. Rectifier check out OK at local shop on their tube tester. Did the "yellow sheet" mod this morning and getting another rectifier ( non JJ) and will try again.  Interestingly enough was driving some Paradigm Studio V10 listening to Ray Brown both times this happened. (great low bass)  Maybe the quad cap is reaching it's useable life?  Amp build was 7 years ago. Thoughts appreciated.
    The 5ar4 will have a hard time if the amp is running at full power, when full power
    is needed i would use Si rectifier.
    Also power off/on within 30s is troublesome.

    Any rectifier that has flashed should be replaced ! ( don't trust tube testers on this !!)
    Also, when auditing speakers, note that a tubeamp should never have the
    speakers disconnected while at power.
    Bob Latino
    Bob Latino
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    Post by Bob Latino on Sat Feb 23, 2019 5:34 pm

    Brap wrote:Rectifier arced last week when I got home after bringing the amp in to a local shop to audition speakers. Fuse blew, replaced that and the tube, all good after that. Last night fuse blew again. Rectifier check out OK at local shop on their tube tester. Did the "yellow sheet" mod this morning and getting another rectifier ( non JJ) and will try again.  Interestingly enough was driving some Paradigm Studio V10 listening to Ray Brown both times this happened. (great low bass)  Maybe the quad cap is reaching it's useable life?  Amp build was 7 years ago. Thoughts appreciated.

    Neither the JJ or the Sovtek 5AR4's are long lasting rectifiers. Even the generic Chinese Shuguang is better than either the JJ or the Sovtek. I have found the new Tung-Sol 5AR4 to be very good and it appears to be more "robust" (longer lasting) than either the JJ or Sovtek. It is a little more expensive but is better built.

    Bob
    Brap
    Brap

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    Post by Brap on Mon Feb 25, 2019 5:54 pm

    Problem solved and thanks. Swapped out with a Sovtek I had in my stash, but ordered up a Tung-sol. Thanks much Bob!!
    As an FYI, I went to a local shop to audition the new Paradigm Persona 7F with beryllium mid / upper's. 89-92dB. Brought in my VTA ST-70 for fun. Listened to their Anthem STR 400W amp and then my ST-70 -- same song. Boy were they impressed and I just smiled! GREAT JOB BOB!!
    corndog71
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    Post by corndog71 on Mon Feb 25, 2019 6:33 pm

    Brap wrote:Problem solved and thanks. Swapped out with a Sovtek I had in my stash, but ordered up a Tung-sol.  Thanks much Bob!!
    As an FYI, I went to a local shop to audition the new Paradigm Persona 7F with beryllium mid / upper's. 89-92dB. Brought in my VTA ST-70 for fun. Listened to their Anthem STR 400W amp and then my ST-70 -- same song. Boy were they impressed and I just smiled!  GREAT JOB BOB!!

    Those new Paradigm speakers are pretty swanky but too damn expensive! Paradigm used to be the budget speaker kings but even the little Atoms are $300/pr. And I know plenty of people who think that's too much for speakers with hardly any bass. Maybe I'm cranky with age.
    Brap
    Brap

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    Post by Brap on Mon Feb 25, 2019 7:08 pm

    No you are not! I'm in process of auditioning amp and speakers for a friend without a budget. Mcintosh 1.2 Kw mono blocks and Sonus Faber Aida's seem to be the flavor of choice for me right now. (He already bought a C-1100 Mac preamp) Nice to have friends with cash!
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    Drummerboy2

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    Post by Drummerboy2 on Sun Apr 28, 2019 3:50 pm

    Brap wrote:Rectifier arced last week when I got home after bringing the amp in to a local shop to audition speakers. Fuse blew, replaced that and the tube, all good after that. Last night fuse blew again. Rectifier check out OK at local shop on their tube tester. Did the "yellow sheet" mod this morning and getting another rectifier ( non JJ) and will try again.  Interestingly enough was driving some Paradigm Studio V10 listening to Ray Brown both times this happened. (great low bass)  Maybe the quad cap is reaching it's useable life?  Amp build was 7 years ago. Thoughts appreciated.

    I had a JJ GZ34 in my VTA-120 are it flashed. I then put that JJ into my Woo Audio WA6 and it flashed in there too. So when I pulled the tube and looked at it closely, there was some metal particles moving around in the tube. The JJ Rectifier is the best sounding to date I had but this was not durable at all. I replaced it with a Mullard GZ37 on the recommendation of SkiZo and all has been great ever since. I'm gonna pick up another one as a spare.
    corndog71
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    Post by corndog71 on Tue Apr 30, 2019 11:17 pm

    Drummerboy2 wrote:
    Brap wrote:Rectifier arced last week when I got home after bringing the amp in to a local shop to audition speakers. Fuse blew, replaced that and the tube, all good after that. Last night fuse blew again. Rectifier check out OK at local shop on their tube tester. Did the "yellow sheet" mod this morning and getting another rectifier ( non JJ) and will try again.  Interestingly enough was driving some Paradigm Studio V10 listening to Ray Brown both times this happened. (great low bass)  Maybe the quad cap is reaching it's useable life?  Amp build was 7 years ago. Thoughts appreciated.

    I had a JJ GZ34 in my VTA-120 are it flashed. I then put that JJ into my Woo Audio WA6 and it flashed in there too. So when I pulled the tube and looked at it closely, there was some metal particles moving around in the tube. The JJ Rectifier is the best sounding to date I had but this was not durable at all. I replaced it with a Mullard GZ37 on the recommendation of SkiZo and all has been great ever since. I'm gonna pick up another one as a spare.

    Tubes are not built in clean rooms. Debris happens. Tube shorts happen.
    Pillo69
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    Post by Pillo69 on Wed May 01, 2019 5:38 pm

    I think that with new tubes influences luck and good utilization.
    I bought a GZ34 RUBI in January 2011, in March it broke.
    I bought a 5AR4 SOVTEK, I placed the diodes 1N4007 and adjusted the input voltage. It's working in perfect condition.
    He's been with a daily use for eight years.
    Although sometimes I want to break to use one of the GZ34 MULLARD (NOS) I bought.

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