geekmacdaddy

Re: Official C12 Clone - Build and Support Thread
« Reply #2560 on: December 23, 2020, 11:59:37 AM »
I don’t resemble the “smarter” claim, but I’m pretty sure you have the common filth issue, get some alcohol and while being super careful to avoid and not melt your polystyrene caps, clean the living heck out of the PCB, Especially where your capsule connects to the PCB, that might help, the cord grounding scheme is exactly as you’d expect, I did nothing out of the normal on mine and it’s noise free👍

Thanks Tony. I have done multiple alcohol cleanings...I'll keep at it. Can you be more specific about the 7pin Jacks? Is there is or is there ain't grounding to the jack bodies?


tonycamp

Re: Official C12 Clone - Build and Support Thread
« Reply #2561 on: December 23, 2020, 04:23:45 PM »
Thanks Tony. I have done multiple alcohol cleanings...I'll keep at it. Can you be more specific about the 7pin Jacks? Is there is or is there ain't grounding to the jack bodies?

Yes there is grounding to body with testing, I get continuity on my mic pin 7 to the outside of the mic body, unfortunately no visual on the inside, I have the bell shield cover on the tranny which covers the 7 pin jack from the backside and it’s a pita to pull that off, Hope this helps

Delta Sigma

Re: Official C12 Clone - Build and Support Thread
« Reply #2562 on: December 23, 2020, 04:45:47 PM »
Did you burn in your tube? Is the noise constant? If you disconnect your capsule and replace it with a 80pF or so cap, does the noise persist? Could it be hum (low f noise, 120Hz or so)?

Did you wear gloves when you worked in the hi-z section of the mic?
Neil Fitzpatrick

geekmacdaddy

Re: Official C12 Clone - Build and Support Thread
« Reply #2563 on: December 23, 2020, 06:56:02 PM »
Did you burn in your tube? Is the noise constant? If you disconnect your capsule and replace it with a 80pF or so cap, does the noise persist? Could it be hum (low f noise, 120Hz or so)?

Did you wear gloves when you worked in the hi-z section of the mic?

Thanks for the response, Delta Sigma. The tube is just vintage. A 12ay7 that could very well be the culprit. I have an NOS 6072 on the way. Suckers are expensive. I wore gloves with the capsule, only. I'll try the 80pf test. Not low hum, a white noise. Here's a sample; https://www.dropbox.com/s/0po1gzyj891ork8/C12%20test%208.m4a?dl=0

Tim Campbell

Re: Official C12 Clone - Build and Support Thread
« Reply #2564 on: December 23, 2020, 08:04:24 PM »
geekmacdaddy what capsule? You should keep alcohol away from any CK12 type capsule.

geekmacdaddy

Re: Official C12 Clone - Build and Support Thread
« Reply #2565 on: December 24, 2020, 07:45:09 AM »
geekmacdaddy what capsule? You should keep alcohol away from any CK12 type capsule.
Of course, Tim. Capsules that touch alcohol shall never touch my mic :D  No alcohol went near the Capsule. It's a Heiserman. I did physically make ground connections in the body of each jack (pin 7 to the body) and am wondering about them. I'll disconnect and see what it does.

Delta Sigma

Re: Official C12 Clone - Build and Support Thread
« Reply #2566 on: December 24, 2020, 11:17:00 AM »
Make sure you do not disconnect your shield. Your mic body should always have a good ground connection.
Neil Fitzpatrick

Tim Campbell

Re: Official C12 Clone - Build and Support Thread
« Reply #2567 on: December 24, 2020, 08:31:01 PM »
as was said earlier. Try substituting the capsule with a  capacitor so you can hear the amplifier and see if it still hisses.

geekmacdaddy

Re: Official C12 Clone - Build and Support Thread
« Reply #2568 on: December 26, 2020, 02:20:55 PM »
as was said earlier. Try substituting the capsule with a  capacitor so you can hear the amplifier and see if it still hisses.

I shall. Had to order that value. I'm assuming disconnect all connections to the capsule and connect the cap at Front Diaphram and BackPlate 1.

Tim Campbell

Re: Official C12 Clone - Build and Support Thread
« Reply #2569 on: December 26, 2020, 04:45:40 PM »
well you can use any available value from 50pf up to 100pf. Capsule values vary a lot. Connect 2 of them, one for each half.

When you talk about hiss, how high is your preamp gain? Could you have the transformer wired wrong and so need more preamp gain to get a decent signal?

« Last Edit: December 26, 2020, 04:51:21 PM by Tim Campbell »


geekmacdaddy

Re: Official C12 Clone - Build and Support Thread
« Reply #2570 on: December 26, 2020, 09:27:06 PM »
well you can use any available value from 50pf up to 100pf. Capsule values vary a lot. Connect 2 of them, one for each half.

When you talk about hiss, how high is your preamp gain? Could you have the transformer wired wrong and so need more preamp gain to get a decent signal?

Good info thanks. Triple checked the wiring, which is correct, and plenty of output.

Re: Official C12 Clone - Build and Support Thread
« Reply #2571 on: January 13, 2021, 09:59:45 PM »
I just built 2 power supplies using pre-owned apex 460 donor enclosures/transformers.  I can set B+ and Bias voltages no problem, but when I try to measure the heater voltage my meter just blinks some values on and off.  Same behavior on both units.
I noticed the resistance was very very low between the 2 yellow transformer wires feeding 9.5v.  1 ohm on one, and 1.2 ohms on the other.  So my meter reads it as continuity.  Is that normal, or could I have ended up with 2 bum transformers?
Does a mic need to be connected for me to get a heater reading?

Delta Sigma

Re: Official C12 Clone - Build and Support Thread
« Reply #2572 on: January 14, 2021, 09:07:21 AM »
Heater is regulated, so probably not. A resistive load would work, need a higher power resistor.

Edited my post because I stupidly left the "not" off of probably not. Changes the meaning slightly...
« Last Edit: January 14, 2021, 01:13:46 PM by Delta Sigma »
Neil Fitzpatrick

Matador

Re: Official C12 Clone - Build and Support Thread
« Reply #2573 on: January 14, 2021, 12:01:34 PM »
I just built 2 power supplies using pre-owned apex 460 donor enclosures/transformers.  I can set B+ and Bias voltages no problem, but when I try to measure the heater voltage my meter just blinks some values on and off.  Same behavior on both units.
I noticed the resistance was very very low between the 2 yellow transformer wires feeding 9.5v.  1 ohm on one, and 1.2 ohms on the other.  So my meter reads it as continuity.  Is that normal, or could I have ended up with 2 bum transformers?
Does a mic need to be connected for me to get a heater reading?
The PSU has a terminal block for heater-.  It's used to reference the output heater- to ground (for +6.3V operation), or heater+ to ground (for -6.3V heater operation).

For C12 you need to place a jumper between heater- and ground, like is shown here (heater- is the left-most terminal block, if the PSU is facing you, with the outputs and polarization knob pointing towards you, as is shown in the picture).

https://groupdiy.com/index.php?topic=51377.msg760350#msg760350

Re: Official C12 Clone - Build and Support Thread
« Reply #2574 on: January 14, 2021, 01:32:39 PM »
Thanks for the help, guys.

Ah yes, thanks Matador.  I completely whiffed on that post.  I swear I've read this entire thread twice!

geekmacdaddy

Re: Official C12 Clone - Build and Support Thread
« Reply #2575 on: January 19, 2021, 12:04:20 PM »
as was said earlier. Try substituting the capsule with a  capacitor so you can hear the amplifier and see if it still hisses.
I rebuilt the power supply (dialed in), rebuilt the mic board, all new. redid the cable, same problem. disconnected the capsule, replaced with 2 47pf caps. Big ground hum, no more hiss.
Is the capsule the problem?
thank you
Jeff

Delta Sigma

Re: Official C12 Clone - Build and Support Thread
« Reply #2576 on: January 19, 2021, 06:16:34 PM »
I rebuilt the power supply (dialed in), rebuilt the mic board, all new. redid the cable, same problem. disconnected the capsule, replaced with 2 47pf caps. Big ground hum, no more hiss.
Is the capsule the problem?
thank you
Jeff

Big hum: is your headbasket removed? That would cause a big hum.
Neil Fitzpatrick

geekmacdaddy

Re: Official C12 Clone - Build and Support Thread
« Reply #2577 on: January 19, 2021, 08:29:05 PM »
Big hum: is your headbasket removed? That would cause a big hum.

Not removed. that loud ground hum isn't there with capsule connected.
« Last Edit: January 19, 2021, 08:34:01 PM by geekmacdaddy »

geekmacdaddy

Re: Official C12 Clone - Build and Support Thread
« Reply #2578 on: January 21, 2021, 01:25:44 PM »
I have found that screwing the body in takes care of the huge ground hum. With the capsule disconnected, getting that white noise with volume on the pre up, and a low volume ground hum with volume all the way down.

any thoughts appreciated
thanks
« Last Edit: January 21, 2021, 01:42:52 PM by geekmacdaddy »

Delta Sigma

Re: Official C12 Clone - Build and Support Thread
« Reply #2579 on: January 21, 2021, 01:46:34 PM »
Can you summarize your troubleshooting? Tube: burn-in and swapping, hiss with capsule and without, etc. It makes it easier for someone quickly browsing the forums to help.

Did you try a new tube? Can you grab one out of a guitar amp? Even if the noise increases with a 12AY7 from a guitar amp it may help you decide the tube is the issue.

When does your 6072a arrive? Is it a Five Star from a reputable source?
Neil Fitzpatrick


 

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