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Sansui G-5700 no sound

ok, I desoldier everything and I got some news.
the transistor all the way to the right (TR16) tested exactly what the thread said, its all good.
now TR18 is not right and same with the TR20, the neg and pos are mixed up...
 
looks like time to build a d.b.t ."dim bulb tester " to limit the current for further testing .
in the meantime if you have diode test function on your meter it would be good to test the diodes on the heat-sink . your meter might not measure them correctly but you could compare one against the other . these diodes control the bias current on the output transistors .something blew the outputs and its possible the right side is bad .
 
how do I build a d.b.t? why did it break now any not other times? I do have a diode setting but it cant get a reading on the diodes, it comes up OL. Should I just solider the other transistor I took out back in?
 
did you try reading the diodes both ways ?
i don't know what broke it that's what i am trying to figure out .
if you do a google search for "dim bulb tester " you will find plenty of info ..
DimbulbSketch.jpg
 
I tried both ways on the diode and nothing different... I did the d.b.t and it got bright when I turned it on but then went down to really dim. I used a 60 watt bulb
 
relay click is good news for left channel then .
parts list is in order then ..
1off 2sa1105 (o,y)
1off 2sc2580(o,y)
thermal paste ..(NOT pc stuff)
1off resistor . 1.2k ohms 1/2watt
i don't know if mouser has the transistors or not .i know my supplier has them and they are pretty cheap
 
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You wont find those transistors.

Use these, I believe they are available from Mouser

NJW3281G (NPN)
NJW1302G (PNP)
 
petehall347 said:
relay click is good news for left channel then .
parts list is in order then ..
1off 2sa1105 (o,y)
1off 2sc2580(o,y)
thermal paste ..(NOT pc stuff)
1off resistor . 1.2k ohms 1/2watt
i don't know if mouser has the transistors or not .i know my supplier has them and they are pretty cheap
Click to expand...

ok I found the 2a1105 & 2sc2580 from your supplier. what does (o,y) mean? or what does 1off mean? does your guy have the thermal paste and where is this resistor that I need located on the receiver? I only took off transistors...
 
lambord said:
ok I found the 2a1105 & 2sc2580 from your supplier. what does (o,y) mean? or what does 1off mean? does your guy have the thermal paste and where is this resistor that I need located on the receiver? I only took off transistors...
Click to expand...

i think its best to take kev zeps advice and go for the subs from mouser .. the resistor is the one that was smoking to begin with . r58
1off means 1 of that part .maybe its just a uk thing ?
 
just been looking on mouser .thing is i don't know what everyone uses over there .too many choices .. we only get one choice i know about . and that's made by servisol .
 
be sure to put the replacement transistors in the correct places . NPN for NPN .. PNP for PNP .
also it would be a good idea to turn the bias down before powering it up first on dim bulb tester .
i will post instructions on setting the bias soon..
 
there seems to be a very bad error in the manual ..it would end up having 15 amps on the outputs setting the bias the way they are saying in the manual .it should be 10ma . i will start a thread about it . maybe this has been corrected in the past .
 
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