Marantz 250 - Troubleshooting Common Issues; Troubleshooting Symptoms; Troubleshooting Procedures

TROUBLE ANALYSIS
The following section is designed to assist in locating troubles.
situations where problems may be difficult to isolate.
through service bulletins (supplementary to this manual) that will be issued to all service stations. It is
assumed that normal trouble-shooting techniques (i.e., point-to-point signal tracing, oscilloscope analysis,
etc.) will be used to isolate problems.
The information given is to help in
Any field problems that arise will be covered
NOTE: Performance verification is necessary following any repair.
SYMPTOM
1.
Excessive line consumption (100 watts or
more
PROCEDURE
Check for shorted rectifiers CR301 through
CR304, CR305, or CR306. Also check C1, C2.
Check for shorted transistors Q802 through
Q805, Q507, Q508, Q510 or Q511. Check
for open control R224, 215-1005-1 bias
assembly. Check T1 for short.
CAUTION: Because thedriver and output stages are direct coupled, components may fail as
a direct result of an initial component failure. If a shorted semiconductor is found, be sure
to check the remaining driver and output components for short or open circuits before
re-energizing the amplifier.
After replacement of any of these components, increase the
Variac voltage slowly while monitoring the wattmeter as described in paragraph C of
Performance Verification.
No line consumption or zero bias.
High DC voltage at loudspeaker terminais
before time delay circuit is deactivated.
High DC voltage at loudspeaker at all times.
No DC Balance.
High hum and noise level.
Parasitic Oscillation.
a.
Check line cord, fuse, transistors Q507, Q508,
Q510, Q511, Q802 through Q805, 215-1005-1
bias assembly.
Check for open rectifiers CR301 through ,
CR304, CR305, CR306 or open T1.
Check transistors Q301 through Q303 for teak-
age, shorted, or open.
Check R301 through R305 for open and Q301
through Q303 for leakage, shorted, or open.
Check Q501, Q502, R502, and Zener diodes
CR501 and CR502
Check R501, R503.
Check filter capacitors, C1, C2, C501 and
C504.
Check for defective C506, C509, C516, and
C505.
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