MK47 PCB tube mic kit - build thread

The whole thing looks great!  I see you use the box the other way up from the Hammond pictures!

Thanks for the heads up on the transformer: I have ordered a couple for my PSUs.  Which choke are you using? What do you use for the pcb blanks?

Thanks for answers when you have time,

David

david-p said:

The whole thing looks great!  I see you use the box the other way up from the Hammond pictures!

Thanks for the heads up on the transformer: I have ordered a couple for my PSUs.  Which choke are you using? What do you use for the pcb blanks?

Thanks for answers when you have time,

David

Click to expand...

Hi David,
I am using the Triad 533-C-3X

This is the board that I used

http://www.mouser.com/Search/ProductDetail.aspx?R=603virtualkey59020000virtualkey590-603

Went to Staples and had them print a transparency. Exposed the board for about 9 min with a "25W" CFL bulb.
First time I ever did a photographic development style and only my second board etch!

I appreciate the compliments 

Dave

feels like i"m carpet bombing this thread.

Here you can see one of the tubes is pulled slightly. Just doing that at the mo to test for continuity and the like.

Doesn't my workjust look amazing. So clean...... :

So why doesn't it frickin wirk :-[

I heard the male equivalent pain wise, of giving birth to a baby is like passing a pineapple out your  urethra or whatever. can that be right? Surely the equivalent is actually to give birth yourself.

Well i feel like I'm doing this with the MK47.

Been up all night working on it. feeling grouchy, slightly tripping and feel really sleepy yet wired!

I've spent nearly £1000 and all i want to hear is this microphone. REALLY! :'(

Thanks for your help in advance

`Yes and the diode is around the right way.

Did you mention there was no voltage at the plate?

"that" would make it not-work. if that's the case I would start troubleshooting that problem.

Cheers,
jb

How can there be no voltage at the plate when my heater voltage is there? my B+ is rocking 105v!

Does the plate connect to the output cap? It's this voltage that's missing ie: 0V on the output cap.

Is the plate the 2/3 pin of the left hand tube when looking down on the pcb in my 1 or 2 photo?

Pin four has the 36V on the left hand tube?

Thanks 0DBFS

muffy1975 said:

Here's photo 3

Showing you from every angle this beautiful microphone that for no good reason will not work

Good gosh!

Click to expand...

There is always a reason. Remember that when you get frustrated. Believe me I'm sure everyone here feels your pain, or at least has been in your shoes. Sometimes its good to give it a break come back to it in a day or two, probably easier said then done when you have some much time/money invested.

But its always something.

I haven't built this microphone (yet) but I couldn't read all your posts without trying to offer some advice.

Check for shorts. Check your wiring. Check your soldering. Clean you PCB with High grade alcohol. And especially watch around the high impedance parts, even oil from your fingers in the wrong spot could cause bad performance/no performance. Switch out your tubes. Check the tube sockets, make sure all the pins are connecting.

Do these things till you find whats wrong. Its usually simpler than you think and it ALWAYS is something.

Oh PS probably not the caps going bad, unless you got the polystyrene cap with alcohol, then you might need to replace it. (the capsule coupling cap)

Good luck!

Well, there are two resistors (100k & 30k) between B+ and plate connection. Check all of those nodes/solder-points for voltage. While you're at it check every node and write your voltages on a printout of the schematic (good for your reference/documentation). Schematic is on page 1 of this thread. You could have a bad solder joint or perhaps either the 100k or 30k has failed or something.

Be careful poking around in there!

Best luck! These mic's are great and there are very few parts so should not be hard to troubleshoot and get going.

-jb

I would also download the datasheets for the tube so you have the pinout and other tube data to reference. Also good to have in your documentation for your mic along with any notes you might make. The schematic shows one tube but there are obviously two of them. I believe the Plates, Grids, Cathodes are in parallel while heaters are in series.

Cheers,
jb

hey muffy youre not alone...

my mic doesnt work too. everything soldered like supposed. volteges are right  :'(

does your mik produce any sound? even some wind noise or something else?

you can put it on a scope feeding the "front" input with a sinus and look if something coming trough...

PERHAPS the tubes (even if marked as nos tubes) are different from ioaudios tubes? i have tubes from an ebay seller because unfortuately one of ioaudios tubes broke? but i really dont know what else to do with this mik.

Without wanting to sound condescending, which I'm definitely not trying to do.

I find when I build something & it doesn't work it's better to not assume that "I've wired everything up right".  It normally works better for me to think on the lines that I have probably done something wrong.

Either way I either have done something wrong or I have a duff component.  In my experiences building stuff with new parts it's not too often the latter......

Anyway if you have no HT present it's extremely unlikely that you have blown every capacitor in the mic. 

One thing I have noticed on this thread is people saying they were supplied with a shorted polystyrene cap.    This is probably unlikely.  It is more likely that the short developed through overheating whilst soldering.  Polystyrene caps don't like a lot of heat.

Hi there gang,

thanks so much for your advice.

i've soldered tens of polystyrene caps before when building 1290's. I've replaced it, but that's not gonna be the problem.

I've switched tubes now quite a few times. The pins seem fine.

I've switched out all the caps now and the problem remains with the temporary replacements so i've switched back. Think they are all OK.



I've built Marshall Plexis from scratch with no pre made PCBS. I've built loads of PSUs including this one. Built 1176 reva revd, igors 2254 and pultec, built 10 silly G1176s. A few pultecs, a few eqs including igors Sontec, built Great River Mp2s, built all kinds of stuff but this problem has me scratching my head. I'm SO methodical with this stuff you know?

I'm gonna keep looking.

Thanks for your support.?

Michael

GOT IT.

it wasn't my fault.

This PCB is not the highest quality. The traces sometimes look cool but aren't.

My problem was the join between the 30K and 100K resistor .........of course. It looked like it was there but wasn't somehow.

Thanks team

Michael

FUCX

this microphone sounds gorgeous. Not having any valve warm up issues yet either.

Will post u47 v TLM103 v SE Gemini very very soon.

God love you all or is that just me  ;D

Michael 8)

Anyone know where I can get the 1uf oil capacitor.......mine has always leaked & stinks rotten horrible smell........thanks

here:

http://www.ebay.com/itm/1uF-300V-1-0uF-MBGO-2-CAPACITOR-LOT-OF-6-NEW-CAPACITORS-NOS-/330708284551?pt=Vintage_Electronics_R2&hash=item4cffbff487

Hi! I'm finally putting my PSU together. But now when I should connect the trafos sec. 6,3 V to the jewel lamp, I can't get any solder on those leads. What should I do instead of soldering them?

And one more thing: Everything but the xlr, binder and the pattern switch are connected and I have measured it. But the values are "walking" between
104,91-105,12 V. Is that a problem or is that what it's suppose to do? I'm using a choke.


Thanks!
John

Do you have any crimp terminals like people use for speaker wiring? That could work.

Dave

Yes, I can see if I find something... I already tried with some kind of "crimps things" (for IEC) but that didn't work. And now when I'm measuring between those two green sec. 6,3 V cables I only get like 0,18 V-0.00.
It should be DC right?

So is the trafos sec not working or am I doing something wrong here. A couple of hours ago, I put them on the lamp with "crocodiles", and the lamp worked. But now I don't get it to work.

The microphone is working and sounds incredible!!

So it's just the light left... If the trafos sec are faulty, is there another way to get 6,3v from that PSU?

What kind os transformer is it? The 6.3V secondary is AC not DC so measure accordingly.

Dave

This is the transformer I'm using:

http://www.tube-town.net/ttstore/product_info.php/info/p2192_Torodial-30VA.html

And the lamp is this one:

http://www.tube-town.net/ttstore/product_info.php/info/p465_Fender-Pilot-Light-Assemply---Lamp-Holder.html

I will measure it again tomorrow. (in AC...)
Thank you!