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8. Troubleshooting Block
4) Set the receiver for AFD or any Sound Field (e.g. Normal Surround), and select a Digital Input to set
up and test the following signal path:
Digital input
⇒
IC1005
⇒
IC1101
⇒
IC1301
⇒
IC1403
⇒
IC1401
⇒
Partial IC1503
⇒
IC1502
⇒
Audio
Amps
****ICs bypassed are IC304, IC1504, IC1554 and Partial IC1503 (Input Circuit)
5) The DSP/SRAM Self Test can be performed to check the operation of the DSP (IC1401), SRAM (IC1402)
and their interface. The DSP also outputs a 1KHz test tone (digital data on IC1404/pins 2, 3 and 4). To
enter the Self-Test mode from the POWER-OFF state, place the receiver in DSP test mode by pressing
and holding the MODE and DIMMER buttons simultaneously while powering the receiver ON. The DSP
outputs data to the SRAM and then reads it back. If the data does not match, an error will be displayed
(internal operation of DSP and SRAM, and the data and address buses are checked). The 1khz test tone
can be used to further section off the digital board. The following signal path is tested:
DSP IC1401
⇒
IC1503
⇒
IC1502
⇒
Audio Amps
****ICs bypassed are IC304, IC1504, IC1554, Partial IC1503 (Input Circuit), IC1301, IC1005, IC1101 and
IC1403
Example of a trouble analysis using above procedures:
Customer complaint: Experiences distortion when connected to the DVD/LD optical input jack. Technician
confirms complaint.
Procedure:
1) Performing the DSP/SRAM Self Test will quickly divide the digital signal path in half. If the self test
passes and there is no distortion in the 1KHz test tone, then the distortion is being caused by one of
four ICs: IC1403, IC1301, IC1101 or IC1005.
2) Now perform procedure number 3 above - the Analog Input test. If the distortion is still not present,
then the problem is with IC1005 or IC1101. If the distortion occurs on all digital inputs including the
coaxial input, then the Optical receiver ICs can be eliminated (not shown on this diagram). The data
on the output of IC1005 can be checked for any distortions (ref. S/P DIF signal waveform figure). If
no distortion is present, the defective component is IC1101.
With a little thought and creativity, most problems on the digital board can be troubleshot to component level
using these five procedures in various orders.
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