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Sansui G-5700 no sound

petehall347 said:
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 .
Click to expand...

You want 3.3mV........

There are test points for setting the bias, one is on the component side and the other is on the trace side.
Its pretty clearly marked in the SM but they say they are both on the component side which is wrong.
I will try to find the thread where this was discussed and there are also pictures.
 
If the Bias reading is taken across the emmiter resistor next to the NPN OP TR (per the schematic), you should be able to read it by placing the probes on the correct jumper wire connections on the 2980 board.
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ghazzer said:
If the Bias reading is taken across the emmiter resistor next to the NPN OP TR (per the schematic), you should be able to read it by placing the probes on the correct jumper wire connections on the 2980 board.
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Click to expand...

i am aware of that . i want to try and make it easier by quoting wire colours .i will look into later .
 
ok after a few pm.s . we now have new bias test points for the right channel .
note where vr4 is set .. it wont end up being much different don't go much higher than original setting .
ok . NO POWER FOR THIS . turn vr4 5 times fully left and right this it clean the track . turn it fully counter clockwise .
power on with dim bulb tester .
vol to minimum no inputs connected
meter set on 200mv dc.
one probe on the left wire of new resistor the other on right one . set to 4mv .if this isn't possible turn amp off and report back .
if that is ok then ...
let amp stabilise for a few minutes measure for 4mv again .
turn amp off .
turn vr4 back to fully counter clockwise
power on no dim bulb tester .
meter probes back on the resistor wires adjust vr4 to 4mv .
let amp warm up and stabilise for 1 minute with probes there .if it starts climbing over 20mv switch amp off
if ok recheck after 2 minutes to see if its still around 4mv .no more than 15mv -20mv .if its climbing turn amp off
if it is looking stable recheck ever few minutes until 20 mins have passed then set at 6.6mv ..
then check the left channel at the same points . don't adjust left channel before reporting back .
 
see the round blue things ? it looks like vr4 will be the one on the right nearest the large heat-sink . it should be marked vr4 on the board . turn it with a small screw driver . don't force it past its end stops .
 
ok we have a problem . NO MORE POWER until we have found the problem
did you put the mica insulators back from under the output transistors ? they are the ones on the heatsink .
vr4 turned fully counter clockwise ?
outputs in correct places ?
if all that is ok check with meter on 200 ohms setting each pin from new outputs to heatsink .
i am suspecting a short circuit .
 
ok I don't know what the mica insulators are so if that can cause a problem then that's probably it. I checked all my connections and it looks like none of them are touching... from what I can tell their is only one way you can out the transistors to make the backs go on the heat sink and line up with the wholes on the circuit board.
 
the metal backing on the transistors also connect to the collectors pins on the transistors ..the metal backing has to be electrically isolated from the heatsink . try your meter on 200 ohms and one lead on heatsink the other on metal backing . low reading is short . we then have to find out why .
if that checks ok then you may have the transistors mixed up . on is pnp the other npn .they have to be in correct places . i am pretty sure i mentioned which goes where in an earlier post .
 
No the relay did not click but the whole units lights aren't even on as if I didn't even press the power button, I turned it on the bias just kept climbing I turned it off when it was at 17 mv
 
something odd is going on here . fist pull all fuses and check with your meter that they are good . if you find any bad ones tell me which ones .
next check for shorts with your meter between pins on new output transistors .
 
on accident I broke one of the fuses and on of the wires somehow came if the diode on the back, it came off the circuit board so I don't know if I can just put that back on of will that hurt it? Also I don't know when that was off so that might have been the prob. I have continuity between all of the pins of the transistors. I broke a fuse as I mentioned before so now I don't know if that fuse was good or not it says 250v2a, I have a new 250v and 6a so I don't know if I can put that in for now or I should go get the right specs?
 
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