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


short test for IC10
Check again whether the marking on the circuit shows the display (ok, already done 100 times)
Use a protective resistor Rp approx. 220 Ohm (against unwanted short circuit), do not connect voltages directly to the PINs.
Connect voltmeter to PIN7
+ 12V via Rp at PIN5 -> PIN7 high, about 12V
+ 12V via Rp at PIN6 -> PIN7 low, about 0V
0V via Rp at PIN6 -> PIN7 high, about 12V
0V via Rp at PIN5 -> PIN7 low, about 0V
Remove Rp

Connect PIN7 and PIN6 directly (analog IC10A) -> PIN7 5V +/- (approximately equal to PIN5); if 12V -> IC defective?
remove the wire PIN7 - PIN6
if no 5V +/- at PIN7:
remove R37
if 5V +/- at PIN7 -> C22 defective ???
if further 12V -> IC10 defective ???

The voltages at PIN7 and PIN1 should be approximately the same.

  • "10k resistors, R39&40. =    10k confirmed.  solder continuity good.
  • 12 volt side of R40, =       11.9v
  • the junction of R39&40 =   3.32v
  • ground side of R39. =      zero"
The voltage should be about 4.2V (Manual), 3.32V is little. If C24 is installed with the correct polarity, this can indicate a defective IC10 ??

vy 73 Reiner

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