SE Electronics Z3300a

[Emmathom]

good mic : 31,4v > R5 (4,7KΩ) > 19,40v
bad mic : 40v > R5 > 37v

 

[micolas]

but where ? Oh my God, we're back in this repair... (crying)

OK
let's make sure monacor transf is ok for sc1100.
1.
Take more pictures if needed, in both microphones.
2.
Put a Monacor transformer in the microphone that works, instead of the stock transformer.

 

[micolas]

good mic : 31,4v > R5 (4,7KΩ) > 19,40v
bad mic : 40v > R5 > 37v

it looks like the Audio PCB is not drawing any current at all
Did you put back all the resistors you desoldered before?

 

[Emmathom]

since the original Tr gives goods resistances (50Ω & 130Ω) maybe it's not the Tr... a Tr is hard to blow away with so little current, no ?

 

[micolas]

Just wanted you to know that Monacor is good for the sc1100

 

[Emmathom]

the good A105 reads 2,32v / 1,6v, while the "bad one" reads 36,70v / 25v !

micolas, I send you an email > please check

 

[micolas]

the good A105 reads 2,32v / 1,6v, while the "bad one" reads 36,70v / 25v !

micolas, I send you an email > please check

measure the voltages on the BJT A1015, on the base, collector and emitter, in both microphones
Ucollector=Ov
measures Udrain jFET

 

[Emmathom]

C1008 : e 34v / b 31v / c 31v
K105 : d 31v / s 0v / g 9,6v

 

[Emmathom]

SA1015 : e36,7v / c 0v / b 25v

 

[Emmathom]

K170 : d 23v / s 3,35v

 

[micolas]

Measure in both microphones and compare.
DC/DC you said it works.
Measure in Audio PCBs.
BJT all pins
jFET all pins

 

[micolas]

Did the microphone with the Monacor make any sounds at the output?

 

[Emmathom]

good mic
K170 : d 14,45v / s 1,62v
1015 : e 2,3v / c 0v / b 1,6v

bad mic is coming...

 

[Emmathom]

bad mic
K170 : d 23,26v / s 3,36v
1015 : e 36,70v / c 0v / b 25v

 

[Emmathom]

Did the microphone with the Monacor make any sounds at the output?

the mic made satured sound with the Tr bad wired... and no sound since I rewired it

 

[Emmathom]

good mic : 31,4v > R5 (4,7KΩ) > 19,40v
bad mic : 40v > R5 > 37v
!!!

 

[micolas]

Disconnect the microphones.
In the bad microphone check the resistors
R5 4.7k and
R6 1.5k
with one end unsoldered from the circuit

 

[Emmathom]

R5 = 4,7KΩ
r6 = 7,5KΩ (despite that this is not what the colors indicate ! (brown-green-black-brown)

 

[micolas]

remove A1015 from the circuit and measure it

 

[Emmathom]

remove A1015 from the circuit and measure it

ok but did you notice R6 is 7,5KΩ unsoldered ? not 1,6KΩ...