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Sansui G-4700 Burning Resistors

N

nicolas25

Active Member
Hello everyone, i have a problem with my Sansui G-4700. Left channel burns the RESISTORS 01 and 05. I already changed the transistors 01, 03, 05, 07, 09, 11, 13, 15, 17, 19, 21 and 23. i changed also the 470uf 50v capacitor for the left channel. also i changed the VR07 for the bias, capacitors 43, 45 and 47 also. resistors 01, 03, 05, 25 and 33 are all new. Planning to change FET1 amd FET2 but cant find replacements. all resistors i guess now are all ok, but upon switching the amp, resistor 05 start to smoke.any idea? i am lost now. sorry for my english im from spain.thanks
 
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Clearly you have a short of some sort.
This can be bridged solder joints, transistor with the wrong pin out ( NPN-PNP switched)
My guess would be, without having all info ( what replacements you used for the transistors) most likely the bias transistor tr05, this has to be a center collector, 2sc945C.
If you give more information it will be easier to advice, was the channel working before?, replacements used?
Do you use a DBT?
 
GrisPato said:
Clearly you have a short of some sort.
This can be bridged solder joints, transistor with the wrong pin out ( NPN-PNP switched)
My guess would be, without having all info ( what replacements you used for the transistors) most likely the bias transistor tr05, this has to be a center collector, 2sc945C.
If you give more information it will be easier to advice, was the channel working before?, replacements used?
Do you use a DBT?
Click to expand...

i replaced c945 for c1815. i bought this amp a week ago without the TR01, TR03, TR07 and R05 installed. at first i installed same replacements, TR01 A1102, TR03 C2577, TR07 i put 2sb528 and place of B527. R05 is 1/2 220 ohm. i dont have a DBT
upon installing the replacements, i powered the amp and R05 starts to smoke. i checked R01 and its also burned
 
Ok, the work you did looks to be good. And apparently the problem existed before, seeing they removed all the involved transistors.
DBT could may be give the opportunity to do some measurements?
 
ive never use a dbt but later i will try to find out how to make and use it. and one more thing, i've never change FET1 and FET2 because i cant find replacements
 
Do the resistors burn instantly or over time?
I do not think the differential FET will be the cause of your problem.
Are you sure the outputs did not short again? ( Oscillating?) And this caused the resistors to burn?
C01-C02 may be shorted?
 
around 3 seconds it starts to smoke. outputs are ok i guess, i test it on circuit.but i will try to pull out later and test
 
Last edited:
hello there, i installed new outputs, new TR01 and 03, new TR07 and 9, new R05 and 01, but still it burns R05 ad also it smokes on the power switch
 
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