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Old 25th March 2009, 02:13 PM   #1
jblmar is offline jblmar  United States
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Default Distorted left channel - Marantz 2385

Greetings,
I'm in the process of repairing a Marantz 2385 (European version). The amp arrived with both channels blown. Repaired both channels. The remaining problem is that the left channel is distorted.
Looking at a 1K sine wave signal, the top half of the signal is missing.
Looking at the base line on the o'scope, the wave is present below the line but not above. Unusual!
Any suggestions?
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Old 25th March 2009, 02:50 PM   #2
h_a is offline h_a  Europe
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Quote:
the top half of the signal is missing
Complementary amp with one half shot?

Have fun, Hannes
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Old 27th March 2009, 05:04 PM   #3
jblmar is offline jblmar  United States
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I measured the voltage at J723 & J725, the base bias of the output transistors. Both measure negitave. J723 should be positive. Reverse biased.
Now's the difficult part. Locating the defect.
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