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Old 31st January 2011, 02:46 PM   #1
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Default Proton AT-200 tuner problem

Hi there,
I've just bought a nice little Proton kit: AM-200 and AT-200. Quite nice litttle pieces of audio. I like Proton, specially the "bass EQ" switch that crank up the sub bass by 12db... I like it !

But ... when I tried the tuner, went into a big problem. SIgnal strenght meter works correctly. I can get full range. But the tuner never show "tuned" neither "stereo" and never stop when in auto tuning. Always muted in FM mode also. I can ear far in the background the audio signal picked from the station.

I tried replacing the MPX IC ( LA3400 ) without success... Still exact same problem.

Anybody would have the service manual or the schematics for this tuner ? Or any help would be appreciated.

Thanks
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Old 1st February 2011, 01:16 PM   #2
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Hi all, now replaced the IF AF amp still with no success; still muted and no stereo neither "tuned" LED on.

Any idea ? Found NAD4150 and NAD 4155 ALMOST the same but not... Using different ICs.

Service manual ? schematics ?
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Old 2nd February 2011, 02:36 AM   #3
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Quote:
Originally Posted by electrochap View Post
Hi all, now replaced the IF AF amp still with no success; still muted and no stereo neither "tuned" LED on.

Any idea ? Found NAD4150 and NAD 4155 ALMOST the same but not... Using different ICs.

Service manual ? schematics ?
look for dry caps with an ESR meter.
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