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Pioneer SX-780 FM tuner alignment - distorted sine wave

Oleg LED

Oleg LED

New Member
I am attempting to align the FM tuner section of a Pioneer SX-780, but I see a distorted sine wave on the scope at step 6. I have connected the test equipment exactly as specified in the service manual (SG at 106MHz with 100% modulation for 400Hz, output at 106dB). The distortions persist regardless of the input signal level. What could be the cause?
 

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Oleg LED said:
The distortions persist regardless of the input signal level.
Click to expand...

What happens if you nudge the Pioneer's tuning? What is the Pioneer's tuning meter showing?

I believe the point of the early parts of the alignment procedure is to make the local oscillator track what the tuning pointer indicates. You could do that using over-the-air signals from strong-ish stations. The OTA signals will be very accurate in frequency (which is not necessarily true of service-grade generators).
 
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