Sansui AU G33X protector at higher volume - diyAudio
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Old 18th October 2010, 06:02 PM   #1
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Default Sansui AU G33X protector at higher volume


I have a problem with my Sansui AU-G33X amplifier. It works fine at lower sound levels, but as soon as I crank up the volume the protector circuit kicks in. After the normal blinking the amp starts working again. I tried and it is only related to the right channel. A few months ago I adjusted bias and checked for DC voltage, so all should still be fine.
Of course this unit is from 1983 and I did not yet replace the capacitors.
Any suggestions where to start looking?

Thanks for your advice,
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Old 18th October 2010, 10:42 PM   #2
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I would check you speakers and speaker wires, one little stray strand of speaker wire touching from + to - will cause this to happenas soon as a little power is added. Or if your speakers are 4 ohm and when you turn up the music it drops down to less ohm's as the the bass is a kick'n, bam, the speaker protection comes on. I have a Sansui and thats what I found would happen. If you have, or, can try a differance pair of speakers I would do that first before digging in to the amp.
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Old 18th October 2010, 10:54 PM   #3
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Originally Posted by Alfanijs View Post
Check otput impedance eg. speaker impedance!
Regards zeoN_Rider
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Old 19th October 2010, 09:54 AM   #4
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Thanks both of you for your replies. You were spot on Rapidroy - it was a stray strand of speaker wire! DC resistance was 1.4 Ohms... Of course I read your messages too late and I discovered this only after replacing all el. caps in the power amp circuitry. Worst thing is I made the speaker cables myself and they had been running without problems on my B2101 power amp, even at higher volume levels - shows again what a beast this is! So I did not suspect the cables or speakers at all.

Everything is fine now. Thanks again!
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Old 30th November 2014, 10:29 AM   #5
fonon is offline fonon  Poland
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I refresh this old thread with similar problem. My amplifier is AU-G50X with the same F-4702 board. The effect is the same as described above but without any load. The protection switches on when the volume knob is at 13 hour. The amplifier works with headphones. I checked the offset voltages. Initially they are close to 900mV! I reduced offsets in both channels to 1mV or below. Unfortunately the bias in one channel is invariant (kVR2 potentiometer doesn't change the bias). The voltage on proper resistor is equal to 5mV instead recommended 10mV. What to do?
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Last edited by fonon; 30th November 2014 at 10:42 AM.
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