Official C12 Clone - Build and Support Thread

[TillM]

Do you measure in AC?
An measure between green and green and yellow wire with yellow wire ?


By the way.
I also build a second one.
My second mic has nearly 6db lower output then the other one.
But it sounds good like the other.
Is it normal and I can brief it as tolerance ?

Edit: Found the fault, one screw from the backplate was not tighten enough. Now they are nearly the same level.

 

[funkymonksf]

I'm building this microphone and have considered using a different PSU case. Using the PSU PCB from Chunger and a 200V & 9V (or possibly 12V) power transformer, how would you recommend connecting a classic pilot light (think ole' tube amp #43 bulbs) to the circuit?

 

[TillM]

I've connect it with the 9v output from the power transformer.
it's easier to get bulbs for it.

 

[plugged1]

I replaced the stock PS mic/out with Neutrik connectors and they are much more solid. I have 2 spare PSU of the OEM and the 7 pin connectors on all wiggle pretty freely which is pretty undesirable after a successful build of such a nice PS.

 

[Matador]

The stock connectors seem to be fine for most uses, however if you are plugging and unplugging the microphone often it's probably worth upgrading to Neutrik or other cable connections.  I tend to leave mine connected and only move the mikes around a handful of times per year.

 

[plugged1]

I get it. I just have different supplies that cannot be crossed with different mics. So I just use 1-7pin cable to help prevent any confusion and not fry something. So I’m unplugging/plugging regularly. Just something I felt to do myself. It’s a preference mod.

 

[doggy6812]

Hey Guys. I am reading 12v at the heater but when I touch the top of the 4700uf cap. It drops to 3 volts . I’ve done this with 3  different caps in the same spot. Any thoughts?

 

[doggy6812]

Hey guys, I have a little issue I have 12 V going to the heater. When I touch the 4700 µF capacitor related to that the voltage drops to 4v. I have changed out three capacitors. Any thoughts?

 

[rmburrow]

I assume the 6072 is wired for 12 volt heater.  Is the 4700 uF capacitor part of a timed circuit to bring the heater voltage slowly up to full value?  Did you leave the 4700 uF capacitor in circuit for any time, with the mic (or suitable resistor) connected to load the heater supply?

 

[doggy6812]

First of all, thank you so much for replying!!  I thought the voltage was supposed to be 6.3v . The voltage, It does creep up. I noticed that the trim pot does not even move the voltage when I turn it. I’ve changed those out too. Scratching my head

 

[Wilks978]

Hey everyone I just built the ELA M251 inspired version a few weeks ago and have been needing some help I'm getting 120v from psu to the pcb, the heater has 6.3 on pcb and tube I had checked ground and everything is well grounded, checked the transformer plenty of times and all seems to be great all my resistors are reading correctly only ones I'm having an issue with are the styroflex 5000pf and 1000pf 100pf caps I get a reading from one of the 5000pf and 100pf but not the 1000pf and the other 5000 I'm trying to be as thorough as possible please help when you can

 

[liquidfuzz]

Hi

I'm planing to build a c12ish microphone. Now I'm trying to source a donor in Europe. Does anyone have suggestions where to find some apex 460, Badaax t11a or similar?

Thanks!

 

[Wilks978]

You can find some bodies on the website studio 939 where they also sell the board for this build and all materials, hope so. Eone can respond to me with the build issue I haven't had any support so far

 

[Matador]

What is the build issue?  It sounds like perhaps you got a few bad caps?

 

[Delta Sigma]

.... Eone can respond to me with the build issue I haven't had any support so far

I read your post on the poctop thread and there is a lot to  process. I'm not sure I understand what your problem is. Is your DC good but there's no audio? What does no audio mean? Completely dead quiet or is there hiss, hum, etc? Do you have B+ at your mic? Is your cable good (continuity check)?

To be honest, most of the times I read the forums I'm at work looking for a quick escape and only have time for a quick read and a half thought out reply. I try my best - probably the same as most here - but it's a diffucult thing to remotely diagnose someone's problem. People here are extremely helpful but sometimes people can be very busy and not have time to troubleshoot others' projects. Please be patient and you'll have a working mic soon.

 

[Wilks978]

What is the build issue?  It sounds like perhaps you got a few bad caps?

I swapped out the styroflex caps with silver mica but still the same I crank the preamp to max and I get low audio coming through

 

[Wilks978]

I read your post on the poctop thread and there is a lot to  process. I'm not sure I understand what your problem is. Is your DC good but there's no audio? What does no audio mean? Completely dead quiet or is there hiss, hum, etc? Do you have B+ at your mic? Is your cable good (continuity check)?

To be honest, most of the times I read the forums I'm at work looking for a quick escape and only have time for a quick read and a half thought out reply. I try my best - probably the same as most here - but it's a diffucult thing to remotely diagnose someone's problem. People here are extremely helpful but sometimes people can be very busy and not have time to troubleshoot others' projects. Please be patient and you'll have a working mic soon.

thank you for your response, and taking time i know it can be difficult, but yeah I'm getting 124v on the b+ side of board, when I turn the preamp up all the way I get low audio and minimal his noise, that I know of my cable is good I just rewired the whole microphone but to no luck, I've been stuck for 3 months now with this build like this, I swapped out the tube twice, I have 3 spare capsules I tried, when I read across the tube I'm getting 6.3v it seems to be that I'm getting 61v polar a cross r13 r12 and c1 something like that, hope that answers these questions.. Could the pcb board be the issue? Also my microphone body was in really bad shape I had to glue one of the metal brackets back together not sure if that would effect anything

 

[Matador]

Did you confirm the primary and secondary of the output transformer are wired correctly?  What tools do you have access to?

 

[Wilks978]

Did you confirm the primary and secondary of the output transformer are wired correctly?  What tools do you have access to?

the red and Brown of the cinemag 13114  1.5k and yellow and orange 300ohm something like that David at cinemag said it was correct specs I wired red to ground and brown to TX correct? And yellow to 6 orange to 5 I swapped them as well  when I check the 1000pf cap to pin 7 on tube I don't get any reading that is supposed to be front capsule to grid correct? I'm using a multimeter all I got sadly

 

[Delta Sigma]

... I'm using a multimeter all I got sadly

You can get pretty far with a multimeter, schematics, ears, patience and willingness to learn.

What is the input impedance of your multimeter? If it's 10M, you cannot get an accurate voltage reading on ections fo the circuits where resistance to ground (or to wherever your lead is referencing) is greater than 1M.

Don't trust your meter's capacitance measurements, especially in the picofarad range. Maybe if you measure a known good cap of the same value, you could look to get a very similar measurement on a cap you're testing.