MK47 PCB tube mic kit - build thread

[zayance]

Yes it's normal for them to get hot, on the safety note i attached to the Etching file i was pointing that out,
by saying "...solder those Hot resistors over the PCB a little to allow some air flow, and save the PCB overtime..."
For some numbers, my 7W resistors were getting to about 90 to 95°C after a minute or two, and that's a point
were you can't touch for more than a sec. Mine were rated to max 275°C iirc, so all good.

 

[wave]

Thanks Zayance. I guess at some point I did read that note b/c I soldered the resistors a little above the board like you stated.

Next question:
I'm wiring my 7 pin connector to the MK47 board and while I was testing my connections, I found continuity between the A+ and A-.
I lifted the A+ off the board and there is still continuity between A+ and A- on the board. Is that correct?

Thanks,
Dave

 

[nashkato]

  I lifted the A+ off the board and there is still continuity between A+ and A- on the board.

depends on where you measure , and what connection you lifted .
but generally A+ and A- is the secondary of the audiotransformer and therefor you measure continuity.

 

[funkymonksf]

Have any of you had any luck with other mic bodies. Besides the t.bone sct-700, alctron, nady 1050, etc... Any mxl, or other cheap donors that work will work, even with a little work. I ordered a t.bone sct-700 and it may be the ugliest damn thing I've ever seen, plus had to return it because the headbasket was extremely crooked.

Any advice would help!

 

[wave]

Have any of you had any luck with other mic bodies. Besides the t.bone sct-700, alctron, nady 1050, etc... Any mxl, or other cheap donors that work will work, even with a little work. I ordered a t.bone sct-700 and it may be the ugliest damn thing I've ever seen, plus had to return it because the headbasket was extremely crooked.

Any advice would help!

Ugly in what way? I got a t-bone and after I filled in the engravings and threw some paint on it, it's a much better looking mic body.
My headbasket isn't crooked tho.

Dave

 

[micaddict]

A little "chrome" goes a long way.

 

[funkymonksf]

I love the look of those stellar bodies! Sexy. Pricey! Know of a good cheap source for them?

 

[Monoklang]

I've been looking at a lot of MK47 pictures in the Group DIY MK47 build thread. And when it comes to how to wire the capsule, it seems like there is a few differences.
I soldered my wires directly on the leads, "above the glass tubes", and front wire to "front", rear wire to "rear" and then this wire from the capsule side goes to the "backplate", is that correct?
I think I've seen people who put the rear to the backplate?

And some solder the wires to the leads under the glass tubes, and some don't, and some directly to the relay pins... Is there a right or wrong? I did my "glass tube leads" exactly a little bit too short to be able to solder anything on them... And I rather don't want to take that structure apart...

Best regards

John

 

[micaddict]

I love the look of those stellar bodies! Sexy. Pricey! Know of a good cheap source for them?

Actually, the Stellar CM-5 and CM-6 are pretty good value for pre-modded/upgraded multipattern tube mics.

But if the question is where to get the shells only but with the chrome, then.......um...................er...............ah.......... :
....... :-\............................good question!

 

[wave]

I've been looking at a lot of MK47 pictures in the Group DIY MK47 build thread. And when it comes to how to wire the capsule, it seems like there is a few differences.
I soldered my wires directly on the leads, "above the glass tubes", and front wire to "front", rear wire to "rear" and then this wire from the capsule side goes to the "backplate", is that correct?
I think I've seen people who put the rear to the backplate?

And some solder the wires to the leads under the glass tubes, and some don't, and some directly to the relay pins... Is there a right or wrong? I did my "glass tube leads" exactly a little bit too short to be able to solder anything on them... And I rather don't want to take that structure apart...

Best regards

John

John,
I was wondering what you think of your Q47-D Capsule?

Thanks,
Dave

 

[Monoklang]

Dave,

I'm waiting for a couple of missing parts for the Psu. Then I will built it, but then I will tell you how it sounds. So until then I have no clue how it sounds. But do you the answers to my questions above? The thing about soldering the capsule wires above the glass tubes?

Regars

John

 

[wave]

Dave,

I'm waiting for a couple of missing parts for the Psu. Then I will built it, but then I will tell you how it sounds. So until then I have no clue how it sounds. But do you the answers to my questions above? The thing about soldering the capsule wires above the glass tubes?

Regars

John

John,
Honestly I can't see why it would matter but if it does maybe Max will chime in. Maybe the glass isolators are just there to give stability to the ends of the pins and keep them from touching the board. I can't see what the difference is in soldering on the top or bottom.

Dave

 

[electrisizer]

unfortunately my mic still dosent work...

i put it on scope feeding the lead of the "front" input and there is no problem. the amplifier gives a clean amplified sinus.

the problem is in the capsule part. neither the beez neeez capsule nor the original behringer sct700 capsule seem to have the right voltage. i just get a very low signal with some distortion...

the last measuring i can take is before the 100M resistor. there is 53V. is this ok? dosent the 100M resistor followed by the 10nf cap reduce the voltage?

any help would be nice.

 

[david-p]

It should work with 53v, although 60 is more optimal.  There should be no voltage drop across the 100M resistor.

David

 

[electrisizer]

It should work with 53v, although 60 is more optimal.  There should be no voltage drop across the 100M resistor.

David

ok i can trim it to 60v (trimable voltage resitor in psu)...

AFTER the 100M i have exactly 5,1V - some say its impossible to measure because of the high impedance. but my meter seems to have no problem. when i trim the voltage bit up or down - this voltage also goes up and down...

and i think thats the way the mic/capsule behaves: 5v polarisation voltage - very low output/sensitivity  :'(

is there any clue for this problem?

 

[david-p]

is there any clue for this problem?

Yes.  What is the resistance of your meter?

David

 

[mrvision]

If you suspect low voltage at the node where backplate, 100M resistor and the 10nf capacitor meet, you may have some sort of short path to ground. Try checking building problems first, like wires, connections, removing flux residue, overflooded Soldering points, etc. if everything looks fine then try swapping the 10nf (0.01uF) cap.

 

[muffy1975]

Guys,

sorry for asking a stupid question but......

In the PSU, where do you connect the orange and red centre tap wires of the TRIAD Xformer to? Do you just connect them to one another and leave them floating and insulted? Or, do you connect them to 0V which is the star ground point?

Kind regards and thanks

michael

 

[electrisizer]

is there any clue for this problem?

Yes.  What is the resistance of your meter?

David

its > 7.8 Mohm

build looks clean. perhaps i have to change the caps. the 10nf seems to be ok if cap testing with the multimeter is trustable...

 

[wave]

Guys,

sorry for asking a stupid question but......

In the PSU, where do you connect the orange and red centre tap wires of the TRIAD Xformer to? Do you just connect them to one another and leave them floating and insulted? Or, do you connect them to 0V which is the star ground point?

Kind regards and thanks

michael

Hi Michael,

Yes you connect them to each other and insulate the end. Definitely DO NOT connect it to 0V

Dave