Fixing old Sansui 5000a, fuse keeps blowing....

Destroyer OS. · 19th December 2006, 09:15 PM

I replaced all the transistors to make sure they will be working. However if I even try to plug it in one of the fuses goes out (left channel). I have nothing plugged in, no speakers, no RCAs, nothing. The speaker position knob is turned to OFF and it still blows any fuse I put in.

Any ideas? I wish I had a schematic :/ There is an endless sea of wires and parts in it.

I realize this means a short somewhere but I am not sure were to start looking as this thing probably has a few miles worth of wiring in it.

Netlist · 19th December 2006, 09:25 PM

Just a quick response, it's bedtime here.
Schematic: Have a look at Audiokarma.com , maybe they have it.
Fuse: If the power supply is a separate one for each channel, check the rectifiers and caps of that side.

/Hugo

Destroyer OS. · 19th December 2006, 10:08 PM

I will take a picture.

The fuses are interesting and appear to be connected to both amplifier boards.

Destroyer OS. · 19th December 2006, 11:18 PM

Destroyer OS. · 19th December 2006, 11:21 PM

There is a small board on the underside as well, not sure what it is doing.

Destroyer OS. · 20th December 2006, 08:09 AM

Well this is going to make a lame Christmas present... Here some decent speakers, a DAC with USB input and a reciever that does not work!

Netlist · 20th December 2006, 11:17 AM

This one shouldn't be too difficult.
First check for shorts between the metal case of the output transistors and the heat sink.
Check every semiconductor on the driver board, diodes included.
Check for burned resistors, replace the caps on that board.
Suspect the bias pot and replace if needed.
This is the best schematic I have so far.

/Hugo

bikehorn · 20th December 2006, 03:14 PM

how about checking for dead electro caps?

Destroyer OS. · 20th December 2006, 08:02 PM

I can not physically see any blow capacitors. I will check for ground shorts, that sounds like a likely problem. How do I know if a diode is bad? That also sounds like a likely problem. Whatever is wrong was most likely caused by over heating.

Thank you so much for helping me!

Netlist · 20th December 2006, 08:08 PM

First, report back on the possible shorts of the output transistors.
What did you replace them with?
Ohh...I just read your first post that says you replaced all transistors. How did you manage to get the originals? Or if you didn't, what are the replacements #’s?

/Hugo

19th December 2006, 09:15 PM	#1
Destroyer OS. diyAudio Member Join Date: Nov 2005	Fixing old Sansui 5000a, fuse keeps blowing.... I replaced all the transistors to make sure they will be working. However if I even try to plug it in one of the fuses goes out (left channel). I have nothing plugged in, no speakers, no RCAs, nothing. The speaker position knob is turned to OFF and it still blows any fuse I put in. Any ideas? I wish I had a schematic :/ There is an endless sea of wires and parts in it. I realize this means a short somewhere but I am not sure were to start looking as this thing probably has a few miles worth of wiring in it.

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19th December 2006, 09:25 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Just a quick response, it's bedtime here. Schematic: Have a look at Audiokarma.com , maybe they have it. Fuse: If the power supply is a separate one for each channel, check the rectifiers and caps of that side. /Hugo

19th December 2006, 10:08 PM	#3
Destroyer OS. diyAudio Member Join Date: Nov 2005	I will take a picture. The fuses are interesting and appear to be connected to both amplifier boards.

19th December 2006, 11:18 PM	#4
Destroyer OS. diyAudio Member Join Date: Nov 2005

19th December 2006, 11:21 PM	#5
Destroyer OS. diyAudio Member Join Date: Nov 2005	There is a small board on the underside as well, not sure what it is doing.

20th December 2006, 08:09 AM	#6
Destroyer OS. diyAudio Member Join Date: Nov 2005	Well this is going to make a lame Christmas present... Here some decent speakers, a DAC with USB input and a reciever that does not work!

20th December 2006, 03:14 PM	#8
bikehorn diyAudio Member Join Date: Aug 2004 Location: toronto	how about checking for dead electro caps?

20th December 2006, 08:02 PM	#9
Destroyer OS. diyAudio Member Join Date: Nov 2005	I can not physically see any blow capacitors. I will check for ground shorts, that sounds like a likely problem. How do I know if a diode is bad? That also sounds like a likely problem. Whatever is wrong was most likely caused by over heating. Thank you so much for helping me!

20th December 2006, 08:08 PM	#10
Netlist diyAudio Moderator Join Date: Jan 2003	First, report back on the possible shorts of the output transistors. What did you replace them with? Ohh...I just read your first post that says you replaced all transistors. How did you manage to get the originals? Or if you didn't, what are the replacements #’s? /Hugo

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