SX-950 Relay Bypassed and Burnt Resistors

[petehall347]

get all voltages on protection board pins . apart from 5 6 7 8 .
all DC apart from pin 12 which is AC

 

[Pageplayer]

Still plugged into 60w DBT, I get..

Pin #1 99mV
Pin #2 -14.3v
Pin #3 97mV
Pin #4 Ground
Pin #5 96mV
Pin #6 97mV
Pin #7 96mV
Pin #8 96mV
Pin #9 30.3v
Pin #10 30.3v
Pin #11 30.3v
Pin #12 5.78v AC

 

[petehall347]

q6 q7 bases voltages ? protect board

 

[Pageplayer]

Q5 Base .37v
Q7 Base 94.1mV

 

[petehall347]

i edited to q6 earlier ... doesn't matter right now though . best check r18 150k

 

[Pageplayer]

pulled a leg on R18, Holdin @ 149.6K

 

[petehall347]

looks ok .put it back and pull a leg up of d5 and see if relay clicks then

 

[Pageplayer]

nope.. pulled a leg on d5.. No relay clicky

 

[petehall347]

what voltage at q6 base ?
thinking about this it would be best to list all transistor voltages BCE in protect circuit to figure this out .

 

[Pageplayer]

Q1 B= .074v
C= 13.3v
E= .098v

Q2 B= .074v
C= 13.3v
E= .099v

Q3 B= -.011v
C= 13.0v
E= -.551v

Q4 B= .005v
C= 12.9v
E= -.546v

Q5 B= .13.2v
C= .343v
E= 13.8v

Q6 B= .331v
C= .125v
E= 0

Q7 B= .174v
C= 30.3v
E= 0

 

[petehall347]

ok q5 readings are mixed up but not important right now .
check r26 68k . if ok replace c6 . if no go pull q5 and see what happens . if no click then q7 is main suspect .

 

[petehall347]

i am under the impression all those transistors are in the correct way round yes ? like originals never been changed

 

[Pageplayer]

i am under the impression all those transistors are in the correct way round yes ? like originals never been changed

Yes.. I checked several times to insure I have BCE were installed correctly, both on P.S. and AWM-062..

 

[petehall347]

q6 should be off even with it not having -1v at its base so q7 should be on .

 

[Pageplayer]

r26 68k Good..
Replaced C6.. No click
Pulled Q5 WE HAVE CLICK!
Immediately shut down after relay clicked..

Replace Q7 ?

 

[petehall347]

test q5 .. could be short c to e .

 

[Pageplayer]

Everything seems to be ok with Q5 & Q7..
No continuity between c to e on Q5, and my two transistor checkers are identifying the BCM legs.

 

[petehall347]

what reading on diode test b to e .....b to c ?

300mv shouldn't be turning it on ..

 

[Pageplayer]

Q5 diode test
C to E or E to C = OL
B(+) to E(-) = OL
E(+) to B(-) = .663
B(-) to C(+) =.657

 

[LesE]

I recall a while back where we had a similar issue that was caused by Q5 with a b-c leakage. This may not show up on a diode test. I'd replace Q5 (2sa733) with a KSA992 if you have one.