Rode K2/NTK 1 R resistor value

[Jakub W]

Hey everyone. I am fixing my broker Rode NTK and found 2 faults. The high voltage capacitors were dead and the R1 resistor in the mic, right after the capsule blew up. I found 2 schematics. In one there is a given value of 3 G (gigaohms?!) and the other is just statung „high value”. Any advice on determining the correct value will be much appreciated.

 

[kingkorg]

Hey everyone. I am fixing my broker Rode NTK and found 2 faults. The high voltage capacitors were dead and the R1 resistor in the mic, right after the capsule blew up. I found 2 schematics. In one there is a given value of 3 G (gigaohms?!) and the other is just statung „high value”. Any advice on determining the correct value will be much appreciated.

3Gig sounds right

 

[Jakub W]

3Gig sounds right

Wow.. Ok thanks a lot. So far I had no luck finding one in online stores. Any hints on that?

 

[kingkorg]

Wow.. Ok thanks a lot. So far I had no luck finding one in online stores. Any hints on that?

Not really, but 1Gig is traditionally used there, i don't think it would make much difference if you used 1Gig.

 

[Jakub W]

I have a really tight budget, so I am also considering a lower value, like 500 M. Anyone has a spare SMD 1 G or similar I could buy and have shipped to Poland?

 

[Khron]

I have a really tight budget, so I am also considering a lower value, like 500 M. Anyone has a spare SMD 1 G or similar I could buy and have shipped to Poland?

Got any cheap chinese Schoeps-circuit mics around?

 

[Jakub W]

Will see, I bough a reeally cheap one to see what its got inside. If this fails, I'll at least have a donor, similar to Newerr to build something OPA based for cheap.

 

[Khron]

Will see, I bough a reeally cheap one to see what its got inside.

Those usually have two 1G resistors inside. With a bit of rewiring, one of them can be removed / "scavenged", leaving the donor circuit still fully functional (and removing the need for the input capacitor).

 

[Jakub W]

Will see, I bough a reeally cheap one to see what its got inside. If this fails, I'll at least have a donor, similar to Newerr to build something OPA based for cheap.

Looks similar to this one, so seems promising:

 

[Jakub W]

Those usually have two 1G resistors inside. With a bit of rewiring, one of them can be removed / "scavenged", leaving the donor circuit still fully functional (and removing the need for the input capacitor).

Thanks a lot for the suggestion Khron

 

[Khron]

Those usually have two 1G resistors inside. With a bit of rewiring, one of them can be removed / "scavenged", leaving the donor circuit still fully functional (and removing the need for the input capacitor).

https://medias.audiofanzine.com/files/genchinamod-472635.pdf

 

[Jakub W]

https://medias.audiofanzine.com/files/genchinamod-472635.pdf

Yep, I missunderstood the instructable. It is a BM 800 - like mic.

 

[Papa Tango Charly]

https://medias.audiofanzine.com/files/genchinamod-472635.pdf

Hello Khron do you have the pdf that explain how to determine the exact R7 and R10 values please? i must be the biasing process.

Here is what It's what it say in the pdf you have posted
pdf to determine exact R7 and R10 values? J305 D and S leads are interchangeable


NOTES: See GenChinaMic.pdf file for original schematic* See file BiasingFETs.

i know a very good video on that topic on youtube but it's an other circuit...


ON the SPA SP1 it's seems like there is 2 resistors R7 and R10 to change?

Thank you best

 

[Khron]

Hello Khron do you have the pdf that explain how to determine the exact R7 and R10 values please?

You can replace them with a 100k-1meg trimpot.

PS. Google is your friend...
https://www.google.com/search?q=GenChinaMic

 

[Papa Tango Charly]

Thank you

 

[Jakub W]

As I found out, the circuit will do me no good, as they use a specific FET instead of the GOhm resistor, but in the meantime I found a supplier, that ships retail quantities to the EU for free https://www.te.com/en/home.html. Will let you know how it goes.

 

[Khron]

As I found out, the circuit will do me no good, as they use a specific FET instead of the GOhm resistor,

I am fixing my broker Rode NTK

FET? Wasn't the NTK a tube mic???

 

[RuudNL]

NTK

 

[Jakub W]

FET? Wasn't the NTK a tube mic???

Yes, I mean the BM 800 that I bought as a donor uses a FET instead of the GOhm resistor, so I can't scavange the resistor from it. I will need to buy the resistor separately in this case.

 

[Jakub W]

NTK

Thanks Ruud, I found the schematic before starting this thread