D-EF47 Tribute To Oliver Archut U47 Build Thread.

Thank you  Can't wait to hear it...

NEWB ALERT!

Sorry in advance, but I'm getting some weird things with my first fire up.
My H+ is showing the right voltage at 5.05V, and it is showing up at pin 5 of the tube.  My B+ is showing 105V at the mic pad, but is also showing 105V at pin 7, 8, and 9 of the tube.  Is that normal?  I'm also not seeing the tube lighting up at all!!  With the correct voltage at the heater, shouldn't I be seeing the the filament lighting up?  I've checked for for shorts in the cable, and checked for continuity where it should be, and it all looks correct. 

I should note, I have an EF800 tube, and a K67 capsule from an old Apex 460 (for testing purposes).

Anyone have any thoughts?

Thanks!

Took a couple readings today...

Voltages at each pin of the EF800

1 - 1.098V
2 - 23mV
3 - 1.108V
4 - 5.05
5 - 30mV
6 - 29.8mV
7 - 105V
8 - 105V
9 - 105V

B+ 105V
H+ 5.05V

Backplate Voltage - .54V

Clearly my BP isn't getting the correct voltage, and my tube filament is still not lighting up.  I've double checked and triple checked wiring, and can't figure anything out.  I've measured for continuity to ground at all of the appropriate spots, and it looks great. I've cleaned and resoldered each questionable solder joint.  But, I still can't get this to be right.  Does anyone have any ideas i can start exploring?  Thanks!

That's a dead tube. Try a new one before doing anything else, as the rest of your build is probably fine.

trans4funks1 said:

FWIW, I added a "load" in parallel to R7 in a simulation and see that the B+ does indeed drop right down town 105vDC.

:-S

This is the second time I  tried to help and goofed up  this thread. My apologies.

Click to expand...

I was confused by this a while ago but Indeed, when you put the plate resistance in parallel with R7, it all makes sense. I used Thevenin's theorem. I haven't had much luck simulating the circuit properly as i don't have good EF80 model in Multisim. What simulation software are you using? Perhaps I just need to estimate some resistances and capacitances and simulate using discrete components instead of a tube.

I was using Duncan PSU designer and an estimated load value.

Can I get a confirmation that when using an AMI BV08r:

1. Orange is p+
2. White is p-
3.  Green is s+
4. Black is s-

Thanks!

Yes, I believe that's correct.

So, this is what I have for the pin out of the mic. I can't figure out what pin 3 is for the life of me. If anyone can shed some light, I'd really appreciate it. I'm very much a beginner.

Pin 1: A-
Pin 2: A+
Pin 3: ??????
Pin 4: H+
Pin 5: B+
Pin 6: PTRN
Pin 7: GND

I believe pin 3 is another ground connection.

There is a jumper on the PSU PCB named 'SHLF' which you can use to ground lift the shield/ground on pin 3 if necessary. I guess so you can have separated 0V electronic ground and housing/chassis/XLR ground. It could also be possible to have adedicated heater ground on pin 3, which connects with the other grounds at the 7pin XLR socket on the PSU.

But inside the mic you can connect pins 3, 7 and the connector housing together to give you as much copper as possible for the ground path.

At least that's what I think is intended, someone please correct me if I'm wrong!

Thanks Banzai!  Turns out it was a bad tube.  I threw another one in there and it fired right up.

I am having a small problem with my B+....  The highest voltage I can get is 94 VDC.  Any thoughts or recommendations?

Thanks

wimmy7986 said:

Thanks Banzai!  Turns out it was a bad tube.  I threw another one in there and it fired right up.

I am having a small problem with my B+....  The highest voltage I can get is 94 VDC.  Any thoughts or recommendations?

Thanks

Click to expand...

PSU PCB
can you confirm this configuration ,
B+
R1 = 20K 2W
R3  = 20K 2W
R8 = 25K pot.

if so then you could reduce the value of R1 and R3 on PSU PCB respectively to allow some more voltage to show up at B+ asuuming all is correct ,
Best,
Dan,

new picture Added on page 1 for capsule connection ,

Picture Refers to dual tube version but the same Scheme applies to the D-EF47  just forget about the other tube except that all the same

Thanks Dan!

I checked those parts out, and they are correct in my PSU.

What would you recommend I replace them with value wise to get the voltage up?  18K?  I don't have any 2W resistors on hand so i will have to order some stuff.

Thanks

Can someone point me to the correct replacement for the following part:

Vishay/Sprague V-730P105X9250

It is not available on the Mouser BOM. Has anyone found a direct replacement?

Also, What are people using for labeling the polarity switch on the PSU? label maker? Anything with the actual polar patterns on them?

Thanks!

[email protected] said:

Can someone point me to the correct replacement for the following part:

Vishay/Sprague V-730P105X9250

It is not available on the Mouser BOM. Has anyone found a direct replacement?

Also, What are people using for labeling the polarity switch on the PSU? label maker? Anything with the actual polar patterns on them?

Thanks!

Click to expand...

what about this one ,

http://ca.mouser.com/ProductDetail/Vishay-Roederstein/MKT1813510255/?qs=sGAEpiMZZMv1cc3ydrPrF9YnoK4MhZ%252buq9jXZORPslk%3d

Best,
Dan,

Excellent! Thanks. This is my first mic build. Still waiting parts to come in.

I noticed that there weren't any mounting screws for any of the connetors that mount to the PSU chassis.

Is there a standard screws-bolts/size/head that is used for mounting everything? Special macine bolts or can I pick them up at the hardware store?

Sorry if these are simple/dumb questions.

Thanks

^Nevermind on the screw question. Figured it out.

I'm having a problem figuring out  which way an AMI T47 transformer mounts on the board.  The transformer itself has no indication of which pins are A-B or C-D.  I looked at AMI's website and they show a bottom pic of the transformer with A-B and C-D but there is nothing that indicates which pins are which.  How can I determine A-B and C-D on the T47?