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    ST 70 failed R.M. start up test


    Posts : 71
    Join date : 2010-09-03

    ST 70 failed R.M. start up test

    Post by Dingojazz on Sat Mar 31, 2018 11:48 am


    A while back posted regarding low bias for ST 70.  Since then trying to troubleshoot via various diagnostics.  Bob
    L. suggested likely quad cap issue, which turned out to be the case.  

    With new quad cap installed per VTA instructions (80uf to the rear), attempted start up per Roy's initial instructions: (left side power tubes and rectifier only.)
    Even with bias turned down, V3 voltage climbs over .6 and V2 appears to get nothing at all.

    Wondering what the indications are for these results..?



      Current date/time is Sat Mar 23, 2019 3:43 am