SE Electronics Z3300a

[Emmathom]

A1015 = hFE 206 / Ic 1,9mA / Vbe 624mV

 

[micolas]

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

that's how it should be
R6=7.5k

 

[Emmathom]

that's how it should be
R6=7.5k

ah... you said fist 1,5KΩ

 

[micolas]

remove the jFET from the circuit and measure it
and
R8
R10

 

[micolas]

ah... you said fist 1,5KΩ

I saw wrong, you are pressuring me to think, translate, write, etc

 

[Emmathom]

IDSS 5,0mA / Id 0,41mA / Vg 281mV / Id(2) 0,00mA / Vg(2) 545mV

 

[micolas]

do not solder jFEt back in the circuit, solder only A1015 and resistor R6 (7.5k).
put in series with R5 (4.7k) a potentiometer (semi-adjustable resistor) of 25...50kohm, adjusted to maximum value.
Power the microphone and adjust the potentiometer to get the same readings on the BJT as in the good microphone,
and after R5 (4,7KΩ) - 19,40v

 

[Emmathom]

I think you won't believe me but even with 50KΩ + 4,7KΩ I still have +43v after R5...

 

[micolas]

I think you won't believe me but even with 50KΩ + 4,7KΩ I still have +43v after R5...

with A1015 connected?

this means A1015 is faulty
Do you have another similar PNP BJT?

 

[Emmathom]

this means A1015 is faulty
Do you have another similar PNP BJT?

I have 1015 spare...

 

[micolas]

put the good A1015 in the circuit, but also measure it before, although I don't trust that tester of yours at all
With the potentiometer set to 50k

 

[Emmathom]

SA1015 changed for a new one and RV 50KΩ desoldered so 4,7KΩ only = 43v still...
re-put the 50KΩ in serie : same 43v

new SA1015 : hFE 137 / Ic 1,3mA / Vbe 624mV

 

[micolas]

hope you have connected R6 7.5k back
don't desolder 50k!

 

[micolas]

Are R8 R10 R11 good?

 

[Emmathom]

original 1015 of the board

 

[Emmathom]

Are R8 R10 R11 good?

not tested > I do it ...

 

[Emmathom]

R10 3KΩ / R8 20KΩ (there's no R11)

R8 must be drain R and R9 source R

 

[micolas]

R6 7.5k is connected???

 

[Emmathom]

R6 7.5k is connected???

yes

 

[micolas]

R10 3KΩ / R8 20KΩ (there's no R11)

R8 must be drain R and R9 source R

R11 is in parallel with capacitor C7 22uF