Dany Bouchard D-12 Build - Pattern select not working and draining voltage.

[Wordsushi]

Ugh. Unfortunately, C11 is showing resistance. I checked each of the caps afterwards and they're all showing resistance, too.

 

[RuudNL]

The only thing between the rotary contact of the swicth and the 'pol' connection, is a 1 M. resistor and a 2.2 uF capacitor.
So if you have a voltage coming from the switch and no voltage on the 'pol', there is not very much that can be wrong! 

 

[Wordsushi]

Yeah, it's extremely frustrating. I don't know why this isn't working and I can't figure it out. It's a shame there's no dedicated support thread like with Matador's C12 build. This is such a simple build, too. I have to figure out what my options are at this point, but this is really stressing me out.

 

[Wordsushi]

Okay, new observation. Perhaps this can shed more light on the situation on the cause (or maybe it's a separate issue). I just noticed that when I turn the dial to full figure 8 and measure B+, the voltage drops from 120 and keeps dropping.

 

[RuudNL]

It looks like the +120V is shorted with the switch in figure-8 position.
Check the wiring to the switch.
On one end of the 8-resistors series circuit there should be +120 V (or so, Figure-8 position), at the other end 0 V. (Omni position)
It might be that the wires to the switch are reversed! (+120 V on the rotary contact of the switch maybe?)

 

[Wordsushi]

You've gotta be right about the short. I did check the wiring and it's right, according to the build guide. I also checked the first and last points of the rotary switch and do have 0 at Omni and 120 at Fig 8.

However, I noticed that the voltage drain (measured from Ground and B+) actually happens one click to the right from straight-up cardioid (switch position 6), it's just slow and drains faster and faster with each click to the right.

Also, just in case this info helps to solve this riddle. Here are the voltage readings (measured from Ground and Pol Mic) for each rotary position:

1 (full omni) - 0v
2 - 11.1v
3 - 18.5v
4 - 25.3v
5 - (Cardioid) - 32.6v
6 - 41.6v
7 - 54.5v
8 - 75.0v
9 (fig 8 ) - 116.2 (not 120, probably because of fast drain starting at position 6)

I have another rotary switch on hand. I'm contemplating installing a clean batch of new 392k ohm resistors chained across it and replacing the stock rotary. Not sure if it will help fix the overall issue, but as you said, there's obviously some kind of short beginning at position 6.

 

[RuudNL]

Another quick test:
Don't go from the rotary contact of the switch to the PCB, and from the 'pol' to the XLR connector, but connect the rotary contact of the switch directly to the XLR connector (where the wire to the 'pol' connection was).
There will be loud 'thumps' when you turn the switch (because the voltage is not filtered anymore) and eventually there will be a little hum, but the different directional patterns should work now. (I don't have the impression that there is something wrong with the switch!)
If this doesn't work, I don't know...

 

[Wordsushi]

Okay, this seems really odd. I did as you suggested. I took the green wire coming from the rotary that goes to "Mic Pol" in the 3 block terminal out of the terminal and also did the same for the white POL wire (that comes out of the 5 block terminal) which goes to pin 4 of the 7 pin out. But when I turned on the PS, I got 0v on the green wire whereas when it was in the terminal block I would get voltage (measured on the terminal block screw above it) based upon the rotary position. But unattached from the rotary, there was no voltage at all on the end of the green wire. I measured at the wire's end and at the spot where the wire comes from the bottom of the rotary and both were 0v.

I then reconnected the wires to their respective terminal strips and, again, found the corresponding voltage. I don't understand why that voltage was not there when the wire was taken out of the terminal block, but there when placed back in.

Ugh. This build has been so stressful.

So here are the questions in my head right now:

1) What to try next to fix this?
2) Would it make sense to re-install the original, stock Alctron PS board and try that? Would it even work with this mic?
3) Perhaps try another power supply build, like the one for Matador's C12, which appears, at first glance, to be nearly identical in design .

 

[RuudNL]

I think that when I would have had the power supply in front of me, I would have traced the problem within 5 minutes.
Unfortunately I can't look through an internet connection, and I am also not a voodoo doctor, who can cure a problem from a distance. 
But I am sure that it is something very simple you just may overlook!

 

[Wordsushi]

I have no doubt you could, Ruud. No doubt. Unfortunately, my lack of experience in such matters has extremely limited my ability to troubleshoot and solve this issue. I'm sure it's all due to "user error" somewhere in the PSU build, but I don't have the knowledge to fix it. It's a real bummer because I think this could be a fantastic mic.

Thank you for trying though, Ruud. Its a shame we couldn't get it fixed.

 

[KrIVIUM2323]

Hi,
Have you checked your wiring? Most of the time this is were errors are in diy mics.

 

[RuudNL]

Yes, that is what I suggested before.
The fact that the +120  V. (or something in that order) drops when the pattern switch is in the figure-8 position, almost confirms this.
Let me put is like this: the switch with the 8 resistors is nothing else than a voltage divider, almost like a potentiometer.
Look at the drawing: in the left drawing, the output voltage can be varied between 0 and 120 V.
In the right drawing two wires have changed position.
The result: There is always 0 V on the pattern wire, resulting in an omni directional pattern in all positions of the switch.
When the switch is in the figure-8 position, the incoming voltage is shorted to ground!

 

[Wordsushi]

Hi,
Have you checked your wiring? Most of the time this is were errors are in diy mics.

Yeah, I hear you. I actually have. The wiring inside the mic checks out and I have continuity from pin 4 to the rear diaphragm connection point. I have clean signal coming from the capsule, but with both diaphragms attached, all I get is omni and there is zero voltage hitting pin 4 on the mic, so as far as I can tell, the problem is happening before the mic. I also tried 2 different 7-pin cables, so it's not the cable.

The wiring inside the PSU all goes to a pair of terminal blocks and I've double, triple checked and more that I have the correct wires going into the correct terminal points.

 

[Wordsushi]

Yes, that is what I suggested before.
The fact that the +120  V. (or something in that order) drops when the pattern switch is in the figure-8 position, almost confirms this.
Let me put is like this: the switch with the 8 resistors is nothing else than a voltage divider, almost like a potentiometer.
Look at the drawing: in the left drawing, the output voltage can be varied between 0 and 120 V.
In the right drawing two wires have changed position.
The result: There is always 0 V on the pattern wire, resulting in an omni directional pattern in all positions of the switch.
When the switch is in the figure-8 position, the incoming voltage is shorted to ground!

So, something is shorting the pattern switch starting on position 6, one click past cardioid, which is where the voltage drain starts. It's hard to understand what that could be since there are no other connections on the rotary at this point other than the chain of resistors... unless one of the resistors is bad.

And here's a new observation. I pre-calibrated the voltage coming out of the power supply (using a 180k resistor in pins 1 and 7 to simulate mic load, as described in the build guide) and set B+ to 120 but I noticed that now, when I plug in the mic and measure B+ from inside the mic, I'm getting just over 140v.

I have no idea what this means or how this is related to the other 2 issues.

 

[KrIVIUM2323]

So, something is shorting the pattern switch starting on position 6, one click past cardioid,

So you have omni to cardio ok AT THE MIC? Put different your mic is working and switch work ok from omni to cardio then from cardio to Bi you have omni?


You mentionned earlier that you changed some resistors on switch yes?Are you sure you did not create a bridge when (if) you soldered/desoldered resistors?

Do you have pictures of the build?

 

[Wordsushi]

Actually, I only have omni inside the mic. The polarization voltage doesn't reach the POL terminal point that goes to pin 4 of the 7 pin output from the PSU.

What I have is variable current at POL MIC on the rotary output (though it's not the right voltage, you can see my POL MIC voltage readings for each rotary position in an earlier post), but for some reason I can't figure, that voltage from POL MIC, doesn't make it to POL.

I did swap out the resistors on the stock rotary to the 392k ohm ones in Dany's BOM and you're probably right that there's a bridge somewhere in that resistor chain. The polarization issue was there before I swapped out the resistors. I should have left the stock resistors in.

I do not have pictures of the build, but I can take some if there are certain things and angles you'd like to see.

 

[KrIVIUM2323]

Ok.
Maybe the rotary switch is faulty.
This should be easy to test,
you have a dmm at hand with continuity tester?
If yes take out from the terminal block the 3 wires (according to build guide/ manual page 70) white, red and green.

From the picture in the build manual i would say that the red one is the "wiper" (same as pattern in Ruud's sketch)  the green or the white one is the ground, the other is b+ in.
So for now turn rotary fully cw (or ccw) and test for continuity between the red one on both the white and the green. Depending on physical position you'll know which one is ground, which one is b+.

Once you have identified the ground, position the rotary the opposite side and check for resistance between "wiper" and ground.

Repeat for each step and then you'll know if there is an issue with the resistors... and the rotary switch.

(If your resistance are 390k you should have  around 3meg at bi position, 1.5meg at cardio, etc,etc...)

 

[trans4funks1]

In the build picture:

Red #1 is the +120vDC that the switch network sees.

Green #2 is the variable vDC return from the switch (which equates to the "wiper" position on a potentiometer) that is used to tune the polarity.

White #3 is ground.


Another quick test will be to bypass the switch and directly connect the turret pin #1 and pin #2 directly to see if a figure 8 polarity pattern occurs.

 

[Wordsushi]

Cool. I will try this. Probably tomorrow morning. I have a second rotary switch and batch of 392k resistors so I'm also going to wire up that switch and do the same test on it as well. Originally, I was going to replace the switch but saw it mentioned (I think) on Chungers C12 build that you can just replace the resistors on the stock switch and I didn't feel like destroying the knob just to get the switch off, but if I can get this second switch working, I might just tear out the original and put it in there.

Can you clarify which turret pins you mean?

 

[Wordsushi]

Okay, hold the presses. What you guys were just talking about, and Ruud's diagram with the voltage divider shorted to ground inspired me to check something. I unscrewed the 7 pin jack on the power supply and, I'll be darned... it appears that the center pin, pin 7, which is attached to the ground, is also attached to pin 4! Now, I'm not 100 percent certain because the wires only have a little play and I can only pull the jack out a little bit and turn it to see pin 4 on the bottom, but I'm either seeing or hallucinating, in between the shrink wrap of the other wires, a tiny glint of a thin wire connecting pin 7 to 4... which, I have to assume, is not supposed to be there. Perhaps for an Apex 460, which this ps is designed for... but it can't be right for this build...

Stay tuned, gents... More info tomorrow when I have some time to properly check this.