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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

    Left channel sounds deminished, lower volume. ST-120

    Mr C
    Mr C


    Posts : 99
    Join date : 2019-07-11
    Age : 69
    Location : Visalia CA.

    Left channel sounds deminished, lower volume.  ST-120 Empty Left channel sounds deminished, lower volume. ST-120

    Post by Mr C Fri Oct 18, 2019 6:25 pm

    I couple of days ago I noticed my left channel had a drop in volume. I swapped the input cables and it stayed on the left channel. I swapped the speaker cables and and it moved over to the right speaker. I swapped the power tubes side to side and it stayed on the left. I swapped the outer driver tubes and it stayed on the left. I haven't put it on the bench yet. What should I be looking for, or at, once I get it on the bench?
    peterh
    peterh


    Posts : 1823
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Left channel sounds deminished, lower volume.  ST-120 Empty Re: Left channel sounds deminished, lower volume. ST-120

    Post by peterh Fri Oct 18, 2019 9:01 pm

    Mr C wrote:I couple of days ago I noticed my left channel had a drop in volume.  I swapped the input cables and it stayed on the left channel.  I swapped the speaker cables and and it moved over to the right speaker.  I swapped the power tubes side to side and it stayed on the left.  I swapped the outer driver tubes and it stayed on the left.  I haven't put it on the bench yet.  What should I be looking for, or at, once I get it on the bench?

    Look for a repair man !
    cci1492
    cci1492


    Posts : 331
    Join date : 2016-05-09
    Age : 63
    Location : NJ

    Left channel sounds deminished, lower volume.  ST-120 Empty Re: Left channel sounds deminished, lower volume. ST-120

    Post by cci1492 Sat Oct 19, 2019 10:27 am

    peterh wrote:
    Mr C wrote:I couple of days ago I noticed my left channel had a drop in volume.  I swapped the input cables and it stayed on the left channel.  I swapped the speaker cables and and it moved over to the right speaker.  I swapped the power tubes side to side and it stayed on the left.  I swapped the outer driver tubes and it stayed on the left.  I haven't put it on the bench yet.  What should I be looking for, or at, once I get it on the bench?

    Look for a repair man !

    Ouch! I would check for cold solder joints, try a new phase inverter, check caps in place with cap checker (unlikely as this is a new build).
    LeGrace
    LeGrace


    Posts : 388
    Join date : 2016-08-07
    Location : Ontario, Canada

    Left channel sounds deminished, lower volume.  ST-120 Empty Re: Left channel sounds deminished, lower volume. ST-120

    Post by LeGrace Sat Oct 19, 2019 1:53 pm

    Double check PIO coupling caps, values should be a close match within pairings.
    avatar
    rjpjnk


    Posts : 262
    Join date : 2018-07-18

    Left channel sounds deminished, lower volume.  ST-120 Empty Re: Left channel sounds deminished, lower volume. ST-120

    Post by rjpjnk Sun Oct 20, 2019 12:14 pm

    Mr C wrote:I couple of days ago I noticed my left channel had a drop in volume.  I swapped the input cables and it stayed on the left channel.  I swapped the speaker cables and and it moved over to the right speaker.  I swapped the power tubes side to side and it stayed on the left.  I swapped the outer driver tubes and it stayed on the left.  I haven't put it on the bench yet.  What should I be looking for, or at, once I get it on the bench?

    Swap the center tube with one or both of the PI (side) tubes to see if anything changes. The center tube has two triodes in it: one for left and one for right. After that it's off to the bench.

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    Left channel sounds deminished, lower volume.  ST-120 Empty Re: Left channel sounds deminished, lower volume. ST-120

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