Traynor YBA300 Questions

Discussion in 'Amps and Cabs [BG]' started by Clark Mement, May 8, 2019.

  1. Clark Mement

    Clark Mement

    May 8, 2019
    I picked up a non-working YBA300, told it has no power and by that I think it meant it does not turn on. It is waiting its turn on my repair bench.

    I am curious about the 12 output tubes. Docs say the amp can shut down bad tube pairs and still operate. Is it possible to test and use the amp with less than 12 tubes installed, say just one pair of output tubes?

    Thank you.
     
  2. Thornton Davis

    Thornton Davis

    Dec 11, 1999
    Canada
    The amp will continue to operate if a pair of power output tubes fail but you should reach out to Yorkville/Traynor through their website to ask them for guidance on this The YBA-300 is a great amp. Good luck with this.

    TD
     
  3. Wasnex

    Wasnex

    Dec 25, 2011
    Per the schematic, the tubes are tied to together in pairs at the cathodes. A relay is placed between the cathodes and ground. I don't see exactly how the relays are controlled, but the owners manual indicates overcurrent in a pair of tubes will cause the relay to lock the tubes out, and engaging the standby switch will reset the relays. If the lockout conditions persists the tubes should be replaced.


    So yes the amp is designed to continue working if some of the tubes go bad. But something to consider is removing tubes from the circuit changes the expected impedance. Basically if half the tubes stop operating, the expected impedance doubles. Given this, running the amp on one pair of tubes would create a pretty severe impedance mismatch which could potentially result in instability or the development of flyback voltages that could punch through the transformer.

    What I would do is pull all of the tubes and bring the amp up on a variac, so I could check all operating voltages on all of the tube sockets. Explanation: The high voltage supply on some of my vintage amps will rise above the filter capacitor voltage ratings if I run the amp without tubes. I suspect this will not occur with the YBA300, but using a variac would allow me to check the amp using a lower line voltage.

    Before doing anything, I would probably open up the amp and do a visual inspection for burned parts.
     
  4. Wasnex

    Wasnex

    Dec 25, 2011
  5. Clark Mement

    Clark Mement

    May 8, 2019
    Thanks everyone. Will keep you posted.
     
  6. Roland GR 88

    Roland GR 88 Commercial User

    Sep 16, 2013
    Ontario Canada
    Retail store manager
    If you call Traynor you'll be put through to the guy that built it.
     
    Fishheadjoe likes this.