Re: [help] Only noise being seen while IQ balance / phase lo / phase hi.

Jose Tent
 

So just to kind of gather my thoughts.......and summarize for the benefit of those trying to help me. 

Symptom: 
  • No tone for IQ balance / phase lo / phase hi even with volume pot turned to the right. 
  • value at IQ balance / phase lo / phase hi is zero with graph jumping up/down randomly.  (Assumed to be just noise)
  • While doing BPF adjustment, the volume of the tone goes up suddenly from near zero to almost 100% in a very small range around the middle. 

Things Checked and thought to be validated:
  • All torroids and its continuity.    (T1 has been checked at least 5 times thoroughly now) 
  • Proper install of Volume pot.  (value slides smoothly from 5k to zero as measured on the board)
Items found to be inconsistent with spec outlined in the manual:   Few items that are way out of spec in RED.  Input voltage is 12.36V.
  • IC6       Pin #3,5 measures around 2.5v  [manual = 1.5ish v) *within tolerance ??*
  • IC7       Pin #3,5 measures around 2.5v  [Manual = 2v]     *within tolerance ??*
  • IC8       Pin #5 measures around 2.37v  [Manual = 0.67v]
  • IC9       Pin #3,5 measures around 2.5v [Manual = 0.65v]
  • IC10     Pin #1,2,3,7 measures 12 volts [Manual = 5.83v]      ??!!??!! 
  • IC10      Pin #4,5 is measuring 3.02 and 2.31v  [manual = 4.21 and 3.94 ]     *within tolerance ??*

Summary: 
The excessive voltage in IC8, 9, 10 shows issues.  Just not sure how that is happening. Continuing to troubleshoot. 

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