Sansui AU-3900

mot on/off · 19th March 2006, 09:33 PM

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 !!

Leolabs · 20th March 2006, 12:26 AM

What's the "strange" thing???

mot on/off · 20th March 2006, 05:19 AM

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

Vidalgo · 28th March 2006, 04:22 PM

mot on/off,
Here you can find schematics for your amp. Not free, but cheap.
Hope it will help.

mot on/off · 29th March 2006, 04:25 AM

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..

Vidalgo · 29th March 2006, 07:19 AM

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.

anatech · 30th March 2006, 02:13 AM

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

mot on/off · 30th March 2006, 08:51 AM

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

mot on/off · 30th March 2006, 08:54 AM

The two "+" outputs only! without the ground..

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

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

dudu · 30th March 2006, 10:29 AM

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

19th March 2006, 09:33 PM	#1
mot on/off diyAudio Member Join Date: Mar 2006 Location: space	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 !!

28th March 2006, 04:22 PM	#4
Vidalgo diyAudio Member Join Date: Jun 2004 Location: Jerusalem	Sansui AU-3900 mot on/off, Here you can find schematics for your amp. Not free, but cheap. Hope it will help.

30th March 2006, 10:29 AM	#10
dudu diyAudio Member Join Date: Jul 2005 Location: Tal-el (galil)	Sansui AU-3900 Hi write here u'r E-mail address and i'll send it to u. Regards Dudu

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20th March 2006, 12:26 AM	#2
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	What's the "strange" thing???

20th March 2006, 05:19 AM	#3
mot on/off diyAudio Member Join Date: Mar 2006 Location: space	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

29th March 2006, 04:25 AM	#5
mot on/off diyAudio Member Join Date: Mar 2006 Location: space	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..

30th March 2006, 02:13 AM	#7
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	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

30th March 2006, 08:51 AM	#8
mot on/off diyAudio Member Join Date: Mar 2006 Location: space	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

30th March 2006, 08:54 AM	#9
mot on/off diyAudio Member Join Date: Mar 2006 Location: space	The two "+" outputs only! without the ground.. +(Left) -----------> O ]----- multimeter + (Right) ---------> O ]---- multimeter

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