Sansui AU-3900

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M

mot on/off

Member
Joined 2006
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 :hot:

Thanx :)
 
M

mot on/off

Member
Joined 2006
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!!
:hot: :hot:
Something is wrong with the output transistors maybe..
 
V

Vidalgo

Member
Joined 2004
mot on/off ,
you noted:
the loudspeakers "scratch" in low volume..
Click to expand...
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

anatech

Administrator
Joined 2004
Paid Member
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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