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allync
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PostPosted: Tue Jul 14, 2009 2:38 am    Post subject: no audio Reply with quote

sylvania rxf169 19c7-16 chassis

adjusted t219 and l221 in audio ckt
touching y223 caused a radio station to come in loud and clear
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jts1957



Joined: 24 Nov 2008
Posts: 2472
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PostPosted: Tue Jul 14, 2009 5:49 am    Post subject: Reply with quote

I'm assuming HAS picture.
from SAMS #2639-2: AUDIO: Inject an audio signal at pin 12 of IF/Sound/Sync IC (IC200) and check for audio at the speaker. If there is no audio at the speaker, check the voltages, waveforms and components associated with pin 12 and Audio Transistors (Q200, Q201 and Q202). If audio is present at the speaker with an audio signal injected at pin 12 of IC200, check the voltages, waveforms and components associated with pins 11, 13, 14 and 15 of IC200. Chack the voltage at pin 11 of IC200, it should measure .97V at MINIMUM volume and 2.4V at Maximum volume.

SOUND IF Alignment:
Tune in a station and adjust L221 for maximum sound. Reduce signal strength at the antenna terminals until distortion appears. Continue to reduce the signal while aligning for undistorted output by adjusting T219.

11=.9V | 12=2.7V | 13=2.7V | 14=1.4V | 15=2.1V
One coil, one transformer, one LC trap, 4 caps plus volume buffer circuitry and , of course IC200 TDA4505A (Is NOT same as TDA4505 no "A").
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