Neumann U67 Clone : D-U67 Tube Microphone Build Thread.

[mickdundee63]

So you have the kk87 with the 4 wires? For the old 87? Or the kk870 with the 3 wires? ( current production 87ai and original/new u67)

It's the kk87. I actually bought an entire head assembly which I understand was from a 1980's u87.

 

[Purplenoise]

It's the kk87. I actually bought an entire head assembly which I understand was from a 1980's u87.

So 4 wires, back plates separated. I could ask and find out for sure but this capsule is not really recommended for newer 87s or 67s I believe, I could be wrong. ( even with the two backplate wires connected together I think people had issues if I remember correctly but again...I could be wrong)

 

[Purplenoise]

It's the kk87. I actually bought an entire head assembly which I understand was from a 1980's u87.

Ok I was wrong, if you connect the two backplate wires together you are good

 

[mickdundee63]

Thanks for checking! Back to the bench.

 

[Purplenoise]

So I building the second psu and although I made it exactly like the first one I am getting 10VAC at the 20VAC input. The H- is staying close to spec at -17vdc unloaded. I suspect a problematic toiroid trafo? I have an extra on order but do you guys think something else is the culprit? Thanks.

 

[poctop]

So I building the second psu and although I made it exactly like the first one I am getting 10VAC at the 20VAC input. The H- is staying close to spec at -17vdc unloaded. I suspect a problematic toiroid trafo? I have an extra on order but do you guys think something else is the culprit? Thanks.

the unloaded voltage of the heater in this psu is exactely -16V -----17V this is fine ,  as it is zener regulated and receive full zener breakdown when there is no load
please increase R2 power to 10W and move off board,
my 2 cents

 

[poctop]

Thank you. I just find it strange that on my first psu I am getting exactly 20VAC and now 10vac with the same parts. Thanks again

you should measure about 26-28V after the rectification bridge unloaded
so 10VAC after the bridge is not a good in this case .
check the wiring of the transformer and what transfomer have you been using ,
refer to page 1 of this thread for the notice about it ,
best,
Dan

 

[Purplenoise]

you should measure about 26-28V after the rectification bridge unloaded
so 10VAC after the bridge is not a good in this case .
check the wiring of the transformer and what transfomer have you been using ,
refer to page 1 of this thread for the notice about it ,
best,
Dan

The 20V transformer is fine since I had an extra one and it gave me same results. Same one I used on my first psu 186b20. The wiring on the toroid is the same as my first psu ( trafo from bom) and I resoldered connections just in case. That’s why I believe that the toroid is problematic. I’ll swap it when I get the replacement early next week. The other two parts in the chain are the power switch ( 2 pole) and socket which I don’t think can cause this issue. Thanks

 

[FarisElek]

Does anyone have any insight on wiring the BeesNeez BV12? It doesnt fit in the PCB, but it's probably close enough that I could wrig it in if I tried.

 

[Purplenoise]

Does anyone have any insight on wiring the BeesNeez BV12? It doesnt fit in the PCB, but it's probably close enough that I could wrig it in if I tried.

Did they give you a wiring diagram for the bv12? I could give you the original Neumann wiring with corresponding wire colors on the d67 pcb. Ask Beesneez for which wire color of their transformer corresponds to what wire color of the original and you’ll be set.

 

[FarisElek]

Did they give you a wiring diagram for the bv12? I could give you the original Neumann wiring with corresponding wire colors on the d67 pcb. Ask Beesneez for which wire color of their transformer corresponds to what wire color of the original and you’ll be set.

I’m going to see if I can get a diagram from them. The original schematic would be helpful. It doesn’t fit in the d67 transformer pcb, but it fits in the classic series aml mount I got just in case.

 

[Purplenoise]

I’m going to see if I can get a diagram from them. The original schematic would be helpful. It doesn’t fit in the d67 transformer pcb, but it fits in the classic series aml mount I got just in case.

I am trying to post the wiring here but somehow I can’t. PM me and I’ll send it to you if you want.

 

[Purplenoise]

Ok here is the wiring for Moby bv12 and haufe bv12 for those interested. Thanks again to Moby and Delta Sigma for taking he time to help me out with this.

 

[FarisElek]

BeezNees hasn't gotten back to me, which is fine. I'm practicing social distancing right now until the outbreak hits where I am and it's obvious who has it and who doesn't. In the meantime, the last thing I have to do is hook up this transformer. I'm fairly new to this so I don't want to make a mistake. I tested the ohms between the pins and maybe it can help y'all to give me some clarity.

Thank you,
Ryan


UPDATE: I wired it like the T67. It looks so similar and has 12 pins and with the ohm reading it just made sense. Anyway. Got it plugged in and it sounds AMAZING. Even with the cheap tube for reading it sounds so good.

THE BAD:
1) R2 is getting hot. It's not melt solder hot. Its more like hot coffee hot. Is that normal?
2) It smells. It smells like hot machine. It smells like an old heat kicking on. Like burning dust. It's not reassuring.
3) D1 zener is hot,  but nowhere close to R2. It's IMO fine.
4) More than 1ohm between body of mic and mic chasis ground. Its like 2-4ohm depending on where I put it.

Ryan

 

[TLRT]

Check back this topic, you have to possibly raise R2 to 40ohm/5W. Calculate the voltage drop on R2 and the Zener.

 

[FarisElek]

Ah jeez. Okay, thanks. I solved the grounding hum. The cable was bad. But R2 is still getting pretty hot, so I'll see if I can measure the drop and if I need a 40ohm.


Ryan

 

[Purplenoise]

Ah jeez. Okay, thanks. I solved the grounding hum. The cable was bad. But R2 is still getting pretty hot, so I'll see if I can measure the drop and if I need a 40ohm.


Ryan

R2 and zener do get hot...and yes the smell is normal. Just make sure your voltages check out in psu. 20vac and around 270vdc at input. Then check b+ and h- with mic plugged in

 

[FarisElek]

You're in USA, right? I'm using that 20v transformer and my R2 is the 5W 22 ohms. Is that what you're using? I'm getting 22VAC-ish split into ~11-VAC at the two inputs and about 268VAC at the AC in.

Ryan

 

[poctop]

1-Just to make sure all is fine ,  measure Voltage drops against R2 and calculate power.

2- As noted before in page 1 of this thread too high powered Trafo will be hard on R2 because of the extra power, then need to dissipate as this simple Zener Voltage Regulator ,  R2 sets the current and Voltage,  so  the( Total voltage -Zener Voltage)
Hits On R2.

3- In Other Situation you might need to adjust to get where it needs to be ,

Best,
Dan,

 

[FarisElek]

That's exactly what's happening to me!