haufe t14/1 in Apex 460

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tony666

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Nov 22, 2004
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I tried to mount a Haufe T14/1 transformer in my Apex 460 but it's not working. I soldered the green wires together like in Duka's Elam clone http://www.cankar.net/duka/Ela_M_Duka.GIF Then I replaced the standard transformer with the Haufe using the same routing and wires as in the original circuit. (apex shematic can be found here http://www.apexelectronics.com/index.php?tmp=13&id= )


One blue wire goes to ground, the other to C8 in Apex schematic. The red wires go to the output. After powering up nothing happens, even the tube isn't glowing. How can I troubleshoot this ?
 
Isn't that a wrong transformer for the Apex? It's made for anode-coupling iirc, but the apex is cathode-coupled..

Check your voltages - and watch where you put your hands!!

Jakob E.
 
Duka's schematic is not carefully documented

Where does the 9V of the power supply go to ? Is it AC or DC. no
attachment indicated on the mic connector schematic , arrhhh !!!!

then there's black arrows around the 6072 tube what is the author trying to convey here ?

Hate to be negative but this is why DIY is misleading. This is why I have not built a lot of projects off this forum. Information that circulates here is not always complete. I see it hurt the beginners most of all. Gives DIY a bad rap. Projects get built and thrown on the shelf after discovering they do not work or work very poorly. Then get listed on black market for sale because the project failed or just lazyness. Until the right information becomes available that parts investment is nothing but parts. Who has that kind of money to let good parts just sit around. DIY needs a lot of improvement. If I had the answers, I would gladly provide them , but I'm learning DIY the hard way too.

Not all projects here are like this , but a majority are. Errors in diagrams, schematics etc etc. damn frustrating to work thru. In fact, I'll only build tried a true designs or have the original near me to make sure nothing is overlooked.

I'll bet there are a dozen individuals who are stuck on this very same mic problem. Time to pull that Mic off the shelf again.

I hope Duka sees this and jumps in on this thread to help this guy out. I know Duka is a good DIY'er was very impressed with his Microphones. We need more Duka's here, but I have'nt seen him around lately , maybe he's busy like all of us.
 
You should check the wiring within the shielded cavity that houses the transformer to be sure that none of the wires leading from the connector to the boards above have been pinched or shorted to ground when you reassembled the body. This is very easy to do on this mike.
 
[quote author="maxwall"]
I hope Duka sees this and jumps in on this thread to help this guy out. I know Duka is a good DIY'er was very impressed with his Microphones. We need more Duka's here, but I have'nt seen him around lately , maybe he's busy like all of us.[/quote]

It's not Duka's project I'm building, I'm only using it as a sorta example for T14 wiring. But yeah he should fix that :green:

Also the Apex shematic has the wrong numbering. 1 at the bottom of the shematic to 7 to match te numbering of the PSU output voltages. Otherwise the filament voltage would be at a strange place ...

Is it true that the T14 can only be used with anode coupling like Jacob said? I could remove the cathode follower in the original circuit.

Thanks already!
 
With that transformer, I'd take out the CF. Here's the schematic for that:
http://www.angelfire.com/ky3/craigorris74/a460schemCFremoved.JPG

I would think you should still get sound through the T14 if it were wired correctly. Sounds like somethings messed up.

Craig
 
This transformer should work in the circuit with the cathode follower. It will just give you a little lower output (14:1 vs. 10:1).
 
It's working again!

I removed the CF and capacitors C9/C10 and R2 . It also has a Peluso CEK12 installed. My first working DIY :green:

I'm not sure but I think it did work in my first attempt, but because the PCB's weren't screwed to the microphone chassis (acting as ground), certain points on the PCB didn't have a ground.
 
tony666

Glad to see the mic is working.....

Could you post some pics of your work with this apex 460 , I'm sure there are others who are interested in turning their Apex 460 or Nady TCM1150 into a C12 or Elam 251 style mic ?

Also, whats is the difference between anode coupled and cathode coupled
would any one care to draw a simple schematic illustrating this ?
 
[quote author="maxwall"]tony666

Glad to see the mic is working.....

Could you post some pics of your work with this apex 460 , I'm sure there are others who are interested in turning their Apex 460 or Nady TCM1150 into a C12 or Elam 251 style mic ? [/quote]

I don't think you wanna see my mess :green: . The schematic Craig posted is what I did.

Also, whats is the difference between anode coupled and cathode coupled
would any one care to draw a simple schematic illustrating this ?

If you compare the original Apex tube circuit and that of Craig or DuKa's Elam clone you'll notice that the output is derived at different points from the tube. The Apex has it's cathode coupled via a cap to the output transformer while the Elam/C12 has it's anode coupled to the output transformer. http://en.wikipedia.org/wiki/12AT7

The next step would be to build the C12 circuit on veroboard. I think that would be easier as long as the power supply can handle those voltages.
 
T666

OK, maybe when you get the mic the way you want it , then post some pics. You've started a great thread on this mic.

Thanks for the anode cathode notes , I understand it completely now.

Which source for T14 did you choose ? Capsule - Peluso ( you stated )?

How does the mic's character compare with the old circuit /mic ?

Also, can the current layout benefit from changing the mics cathode coupling to anode coupling using the same transformer dual triode tube ?


2 versions of the T14
http://www.tab-funkenwerk.com/id2.html


I have noticed thru tube substitution that the factory tubes are very quiet and non microphonic. Surprisingly so for such a inexpensive mic. I have only tried a 12AY7/6072A (electro Harmonix tube) and it was too noisey compared with the factory tube that came with the mic. I'm going to try some others like 12AX7-7025 or 12AV7 .... Also, the electrolytics in this mic C8 (1uf/450V) are 105 degree SR types , not anything I've seen before as a audiophile graded lytic, maybe these can be changed to a known type with decent results, not sure.


Craig, you posted the much needed schematic I've been waiting to see. the Apex 460 and my Nady 1150 appear to be the same mic. I was not able to confirm it until now.

Mic now off the backburner DIY shelf for some new mods.

There have been some reports of using a Mullard 12AT7 and some other mod that is supposed to awaken the mic from its factory delivered state. Does anyone have info on this mod ?
 
http://www.groupdiy.com/index.php?topic=24100&highlight=6072

look at the links to Klaus's
 
Gus,

thanks for the links, good information on tubes and noise floor.

Makes you think hard when looking at the newly advertised gold pinned
tubes available ( ebay etc ) , seems there only good in guitar amps, not microphones.
 

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