How to get the mic running without switches?

[npc00]

So...

How  do I get my U87 DIY clone to run without the switches. The  mic is calibrated to 11.5 volts.

Anything Helps

Thanks !

 

[Khron]

Well, just don't use the switches

Backplate goes into the feedback network, which is connected to the bias voltage (coming from those 330k resistors), and the front diaphragm to the 470p coupling cap (going to the JFET gate) and the first of the two 1G resistors.

You will, of course, be stuck with cardioid only.

See attached schematic.

 

[npc00]

How can I translate this schematic to Danny Bouchards PCB?

http://vintagemicrophonepcbkit.com/DU87.html

Thanks!

 

[Khron]

http://groupdiy.com/index.php?topic=48030.0

 

[npc00]

I am getting no sound on the microphone and I do not know what to do... I followed everything based on the link you sent me.

Much help would be appreciated.

Thank you

 

[Phrazemaster]

I believe Krohn was trying to point you to the main thread for your project  - there are literally 157 pages of posts. Sometimes someone can help you troubleshoot things here, but there’s an attitude that you need to do all you can yourself. I’m not saying you didn’t.

But did you read through all 157 pages of that thread? When I do DIY stuff here I make it a point to read the entire thread (especially if I’m having problems.)

Also have you considered posting to that thread? You’ll probably have better luck there.

Also you can use the search function to zero in on posts that might offer solutions...have you done that?

Welcome to DIY! I hope you can get this sorted. I don't know enough to help or I would.

Mike

 

[iampoor1]

It's also a good idea to post what steps you have taken to troubleshoot the issue. 

 

[camarada78]

One thing that I would like to understand that i could not clearly find on the 157 pages of that thread:

If you are using a single backplate unidirectional k87 type (cardioid only) capsule, should one eliminate:

- R1 because the switch is not connected to anything, so R1 leg is "lifted".
- R3 because it comes straight from the second diaphragm that is non existant.
- R4, R5, C1, C2 and C3 because they look like a balance to the "figure of 8" and "omni" patterns.

Or do they have a function on a cardiod pattern configuration that is not clear to me?

 

[Khron]

Well, the idea is, this is a project to clone the older version of the U87, the one without a DC-DC converter that creates the positive (for cardioid and omni) AND negative capsule bias voltages (for fig-8). That requires a K87-type capsule with isolated backplates.

Regardless, assuming the rest of the circuitry is ok, not using any of the switches, and even with a non-isolated-dual-backplate capsule, one should still be able to use the cardioid response.

As the OP's measurements revealed in the other thread he started on this topic, there's no bias voltage getting to the capsule => no sound.

https://groupdiy.com/index.php?topic=72610.0