SE Electronics Z3300a

[Emmathom]

everything is connected at this moment except R10 / R8 and the Fet

 

[Emmathom]

R11 is in parallel with capacitor C7 22uF

no R11 nor R12 in this mic !

 

[micolas]

Ok, wait

 

[Emmathom]

see...

and the same in the good mic : no R11 / R12

 

[micolas]

replace R3 and R4 with 4.7...6.8k each, even though you don't have any pairs yet
connect all the components on the PCB
JFet and resistances
leave the RV 50k in the circuit

 

[Emmathom]

replace R3 and R4 with 4.7...6.8k each, even though you don't have any pairs yet
connect all the components on the PCB
JFet and resistances
leave the RV 50k in the circuit

4,7KΩ or 6,8KΩ ? I've a lot of 6,8KΩ...

R3 / R4 are 2,2KΩ on the board : what a big change !

 

[micolas]

6,8k

 

[Emmathom]

ok I measure and pair them...
I follow you but it's not "normal" we have to change constructor values, huh ?

 

[micolas]

ok I measure and pair them...
I follow you but it's not "normal" we have to change constructor values, huh ?

the dc resistance of the secondary has increased, so it no longer shunts the Phantom source so much, the voltage available to power the circuit has clearly increased

what voltage do you measure now at the junction between r3 r4!

 

[micolas]

I follow you but it's not "normal" we have to change constructor values, huh ?

that's why it's called
diygroup

 

[Emmathom]

ok everything is replaced and soldered (the 50K too) : what do I do ?

 

[Emmathom]

that's why it's called
diygroup

Tweaky Group

 

[micolas]

ok everything is replaced and soldered (the 50K too) : what do I do ?

power the microphone and measure the junction r3 with r4

 

[Emmathom]

power the microphone and measure the junction r3 with r4

43,33v

 

[Emmathom]

42,60v at R5 = 4,7KΩ + 50KΩ

 

[micolas]

After?

42,60v at R5 = 4,7KΩ + 50KΩ

 

[Emmathom]

400mV through R4 (6,8KΩ)

 

[Emmathom]

After?

yes after

 

[micolas]

on dc/dc how does it measure now compared to the good mic?

 

[Emmathom]

42v at drain !!! something's absolutly wrong