Sanyo AVM-2550S Training Manual page 74

No MTS Function
1. While receiving known stereo and SAP signals, check for audio output
signals on pins 3, 4, 38 and 39 of IC 3401 with and oscilloscope.
A. If signal is not normal, problem is with MTS Processor (IC3401) and/or
associated circuitry.
2. Check Multi-Sound Section alignment per service manual.
No Caption
1. While receiving known Caption encoded signals, check CPU pins 39-42
for 5Vp-p pulses and recheck Captions Menu.
2. Check CPU pin 17 for 2 Vp-p composite video.
No AV
1. Check for proper Low to High switching when selecting AV mode on CPU
pins 7 and 8. (See page 24 for TV/AV Switching Circuits.)
A. If CPU pins 7 and 8 do not switch correctly, check IC801.
B. If pins 7 and 8 switch correctly, check IC101, IC1001, IC1002, IC1081
for video signal switching and IC3401 for audio signal switching.
No S-Video
1. Check for proper Low to High switching at IC1081 pins 9 and 10 when
connecting known S-Video signal to S-Video Input jack.
A. If pins 9-10 do not switch correctly, check IC801 and IC1081.
Color Enhancer
1. With an oscilloscope, check for R and B output signals on pins 28 and 30
of IC101 when selecting "Warm" mode.
A. If pins 28 and 30 do not change, check IC101 and IC801.
No PIP Picture
1. Check PIP 3.3 volt power supply (Q8000, emitter).
A. If no 3.3 volt power supply, check Q8000.
2. Check for clock pulses and PIP control data at IC8001, pins 24-25.
A. If signals are correct, check IC8001.
B. If signals are not correct, check IC801.
3. Check for vertical and horizontal sync pulses at IC8001, pins 32-33.
A. If pulses are correct, check IC8001.
B. If pulses are not correct, check Q881, Q882, Q8005 and Q8006 for
proper sync pulses.
4. Check for TV or AV video signal at IC8001, pin 13.
A. If signals are correct, check IC8001.
B. If TV video signal is not correct, check IC1002, Q162 and IC101 for
proper TV video signal.
C. If AV video signal is not correct, check IC1002, Q1093, Q1094 and
Q1096 for proper video input from external equipment.
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