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Old 19th March 2006, 09:33 PM   #1
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Smile Sansui AU-3900

Hello Everybody!!

I've got the Sansui AU-3900 amplifier, it's 2x22W...
I'm looking for the service manual, because something "strange" happend from my brother !!

Some people sell it on net, but i don't know if any mate got it and can post it please..

Thank a lot !!

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Old 20th March 2006, 12:26 AM   #2
Leolabs is offline Leolabs  Malaysia
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What's the "strange" thing???
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Old 20th March 2006, 05:19 AM   #3
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Goodmorning!!

I mean that he didn't take care and he propably sortcut the output of the amplifier!! Since then the loudspeakers "scratch" in low volume..

I wanted to measure the check points to see what's going on inside the amp, so i can change the damaged components

Thanx
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Old 28th March 2006, 04:22 PM   #4
Vidalgo is offline Vidalgo  Israel
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Default Sansui AU-3900

mot on/off,
Here you can find schematics for your amp. Not free, but cheap.
Hope it will help.
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Old 29th March 2006, 04:25 AM   #5
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Hello,

Thanks Vidalgo, i've got the schematics for the amplifier (schearching a lot at the net) for free.
I found out that if i connect a multimeter (in Volts) at the 2 possitive outputs of the amplifier, red - right & red - left i've got voltage!!

Something is wrong with the output transistors maybe..
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Old 29th March 2006, 07:19 AM   #6
Vidalgo is offline Vidalgo  Israel
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mot on/off ,
you noted:
Quote:
the loudspeakers "scratch" in low volume..
Probably, the only reason for it is defective volume control potentiometer, with loosing wiper contact.
You can check it with ohmmeter, connected between wiper pin and ground.
If readings momentary "jumps" while turning, the potentiometer must be replaced. Sometimes cleaning also helps.
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Old 30th March 2006, 02:13 AM   #7
anatech is offline anatech  Canada
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Hi mot on/off,
You are measuring from ground to the speaker output positive?

I don't have the schematic so here goes some general help.

If your unit has capacitor coupled outputs some DC voltage may be a little leakage that disappears when you hook up a speaker.

If your unit is standard direct coupled (no cap, no transformer), a DC voltage is very harmful to your speakers. Full range or woofers in particular. It doesn't take too many volts to kill a woofer. 4 VDC may be enough for some speakers.

-Chris
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Old 30th March 2006, 08:51 AM   #8
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Hello again!

If i connect the two possitive (red) outputs of the amplifier wih a multimeter, the volume ay 1~2/10 i've got AC voltage!!!
And disturtion at the tweeter!

Schematics
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Old 30th March 2006, 08:54 AM   #9
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The two "+" outputs only! without the ground..

+(Left) -----------> O ]----- multimeter

+ (Right) ---------> O ]---- multimeter
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Old 30th March 2006, 10:29 AM   #10
dudu is offline dudu  Israel
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Default Sansui AU-3900

Hi
write here u'r E-mail address and i'll send it to u.
Regards
Dudu
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