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Thread: Yaqin MC10l

  1. #1

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    Default Yaqin MC10l

    This is my first journey into tubes. Purchased off Audiogon from a highly rated seller. But when I hooked it up this morning it blew the 5 amp fuse after
    about 20 seconds. It started a faint popping in the speakers that gradually
    became louder then one last pop blowing the fuse. I checked all my wiring
    and all good. Then I notice that in my haste I had tubes V4 and V1 [EL34's] reversed according to their labeling so I fixed that. I then replaced the fuse and it blew again. Watching the tubes as it warms up, the popping seems to coincide with a flashing or arcing in tube V4 at the last moment before
    blowing again. The amp came with a spare set of tubes so I have them to try out when I get more fuses.
    The speakers are 1.2TL's and were hooked up both times the fuse blew.
    Most of the popping seemed to come from the right speaker.
    Since this is my first tube amp, any recommendations would sure help.
    Thanks.
    SDA 2.3/RDO's... xovers by Ben
    SDA 2.3TL/Stock..
    SDA 1C/Solens/RDO's [gave to my Uncle]
    SDA 2B RDO's
    Snell Type CV
    SDA 1.2TL's
    GFA7700 Adcom
    GFP750 Adcom
    TFM55X Carver
    M90 Pioneer/C90 Pre
    M91 x 2 Pioneers/C91 Pre
    Yaqin MC10l
    DCD-1520/1560/2560 Denon
    Marantz DVD-8400
    Carver m1.5T
    DV-79avi Pioneer
    TFM35X x 2

  2. #2

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    What brand of tube are you using? Is the V4 tube seated all the way into the socket or just partially seated? Some of the Russian tubes have a shorter base? (not sure if that's the right term) so they don't fit all the way into the socket. In my situation with my MC10-L, the glass portion of the Russian tube was hitting the amp case and didn't allow it to seat all the way into the socket..that bothered me so I never powered the amp on because I was afraid it would arc. Instead, I reinstalled the Shuguang tubes which have a taller (longer?) base and they seated all the way into the socket. Not sure if this info helps.
    Last edited by michaeljhsda2; 09-25-2010 at 03:37 PM.

  3. #3

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    The tubes say Electron Tube, EL34B, made in China. The other set I have is labeled
    JJ E34L. Pins look the same length and appear to seat below the case. The arcing that I
    saw was inside the tube. When tubes are warming up, is it a smooth transition to a glow, or should I see any arcing? I am beginning to suspect a bad tube.
    By the way. This is the Yaqin you linked to here on the forum. It was a indeed a good deal. My wife did not know until it arrived and asked how much it cost. I told her
    it cost 4...... big ones. She sat there for a minute and saw how pretty it was and
    thought, 4 thousand? Had her goin for a good laugh.
    SDA 2.3/RDO's... xovers by Ben
    SDA 2.3TL/Stock..
    SDA 1C/Solens/RDO's [gave to my Uncle]
    SDA 2B RDO's
    Snell Type CV
    SDA 1.2TL's
    GFA7700 Adcom
    GFP750 Adcom
    TFM55X Carver
    M90 Pioneer/C90 Pre
    M91 x 2 Pioneers/C91 Pre
    Yaqin MC10l
    DCD-1520/1560/2560 Denon
    Marantz DVD-8400
    Carver m1.5T
    DV-79avi Pioneer
    TFM35X x 2

  4. #4

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    One more thing. The Chinese tubes have 8 pins and the JJ tubes have 7.
    SDA 2.3/RDO's... xovers by Ben
    SDA 2.3TL/Stock..
    SDA 1C/Solens/RDO's [gave to my Uncle]
    SDA 2B RDO's
    Snell Type CV
    SDA 1.2TL's
    GFA7700 Adcom
    GFP750 Adcom
    TFM55X Carver
    M90 Pioneer/C90 Pre
    M91 x 2 Pioneers/C91 Pre
    Yaqin MC10l
    DCD-1520/1560/2560 Denon
    Marantz DVD-8400
    Carver m1.5T
    DV-79avi Pioneer
    TFM35X x 2

  5. #5

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    Check the bias with a multi meter and report your readings

    Make sure the powers down and the speakers are hooked up when checking with the multi meter. You should be reading between 350 and 400 mv's

    Try using a circuit that has nothing else hooked up to it and make sure your speaker wires aint touching as these amp dont have an auto shutdown feature like most mordern day avr's etc...

    How much money did you pay for this because you can buy them brand new from ebay shipped for like $500

  6. #6

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    Never should arc. Was it the chinese tube that blew? If not, I would install the chinese tubes and then check the bias. Make sure it's between 350 400 mV.

  7. #7

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    I am using the electron made in china tubes

  8. #8

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    Sounds like the Shuguang EL-34B's that came stock with the amp. They work great but you're right, could just be a bad tube or the bias was set too high (perhaps it was biased with the JJ's in it but you reinstalled the Chinese tubes instead...just thinking out loud).

  9. #9

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    I'll have the Fluke meter hooked up the next time I power up and watch the bias.
    Speaker wires are ok. I use bananas.
    It was 4 hundred big ones, with an extra set of tubes, interconnects, no freight, and no
    paypal fees. Cheapest way I have found to try out a tube amp. Just a little bad luck
    at this time.
    SDA 2.3/RDO's... xovers by Ben
    SDA 2.3TL/Stock..
    SDA 1C/Solens/RDO's [gave to my Uncle]
    SDA 2B RDO's
    Snell Type CV
    SDA 1.2TL's
    GFA7700 Adcom
    GFP750 Adcom
    TFM55X Carver
    M90 Pioneer/C90 Pre
    M91 x 2 Pioneers/C91 Pre
    Yaqin MC10l
    DCD-1520/1560/2560 Denon
    Marantz DVD-8400
    Carver m1.5T
    DV-79avi Pioneer
    TFM35X x 2

  10. #10

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    It was in fact the Chinese tube that seemed to arc or flash.

  11. #11

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    Since the amp is manual bias, I'm wondering if having the 2 tubes installed in the wrong sockets made V4 arc and then blow.

  12. #12

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    Sounds like a poor tube.............I hate Chinese tubes in general for this reason.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  13. #13

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    Swapped tubes today and it works fine. Bias all at around 340mv.
    It's a little early to say but my first impression is that the 1.2TL's
    may be a little too much for this Yaqin. Going to try the 2.3's that
    Ben did my xover's next. Thanks.

  14. #14

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    Quote Originally Posted by Neskahi View Post
    Swapped tubes today and it works fine. Bias all at around 340mv.
    It's a little early to say but my first impression is that the 1.2TL's
    may be a little too much for this Yaqin. Going to try the 2.3's that
    Ben did my xover's next. Thanks.
    How does it sound on the 2.3's? Was it not able to drive the 1.2TL's loud enough? It drives my 1.2 TL's to about 116 db in my 13 x 18 ft room with great sound quality.

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