C1 is connected to the pin 9. 0.01mfd.
Neumann U67 Clone : D-U67 Tube Microphone Build Thread.
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egroys
Well-known member
Just built a pair and while one is working, I can only get signal when it’s set to figure 8 on the other. Only from the rear capsule. Omni and Cardioid give me nothing at all. Triple checked all of the capsule and switch PCB connections and everything appears copacetic. Is there anywhere else I should be looking?
Thank you!
Thank you!
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What is your voltage at the R12/R13 junction? R2/C2?
egroys
Well-known member
R12/13 is 49v and R2/C2 is 249mv.
Looks off. I checked continuity in that area and everything seems fine. Anything specific I should look for other than bad joints or no continuity? Is it possible it's a bad switch or something?
Looks off. I checked continuity in that area and everything seems fine. Anything specific I should look for other than bad joints or no continuity? Is it possible it's a bad switch or something?
egroys
Well-known member
Reversed my capsule wiring to the same, inverted result. I guess I just need to compare voltages from my working mic to try to zero in on what the issue may be. Any ideas of how I can narrow down my search would be greatly appreciated!
Edit: the culprit was C2!
Everything is working now. Thank you all!!
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Awesome! Glad you got it working. I should've mentioned that you may get incorrect voltage readings in the Hi-z section, which is why it's important to measure at the voltage divider first. If your voltmeter is loading the circuit you will see a low value (like 10V or so) but shouldn't see mV.
I built a du-67 but I can't get the darn thing to work. I double checked everything and I can't find anything wrong--at first I had forgotten to solder the "audio" trace between the tube socket and the main board but after rectifying this I still had issues. The transformer resistances match up with the ones listed in the documentation, so I don't think it's the issue. B+ and H- voltages both measure correct and are headed to the right places. When tapped with a pencil, the tube passes an audible amplified signal. the pattern and pad switches make loud popping noises when switched. I have tried several known good capsules. It amplifies EMI very well--it picks up the noise from the lights in the room, as well as the PSU. Any help would valued; I am very lost.
Measure DC at the places that have a value indicated on the schematic (ie junction of R9/R10/R11/R12) and post your measurements here. Any hi-z measurements will measure lower than they actually are.
Hello. I purchased the Cinemag 5701 and I can't figure out how to wire it up. Is anyone willing to share how please? There are literally 13 lead wires and I have no clue. I attached part of the spec sheet but I still can't figure it out. Your help is MUCH appreciated!
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The one for the AMI T67?
If you look closely at the transformer on Danny's schematic and the "test ciruit 1" of Cinemag spec sheet you will see, they look the same.
Ignore the resistors on the spec sheet.
But be sure to check the phase dots. That is important especially for the tertiary winding.
So Red with the dot is the same as P1 on Danny's schematic.
GRN is P2, next green is P3, RED without dot is P4 and so on.
If you look at the picture you posted of your cinemag transformer. The lower wires are the primaries (except the blue, white and black wires).
The blue and white wire on that side correspond to P8 and P9 on Danny's schematic. The black wire is the core shield and should be connected to ground.
All the wires on the upper side are the rest of the secondaries and the tertiary windings.
It starts with white which is the white with the dot I suppose. So it would correspond with P5 on Danny's schematic.
I hope it makes at least a little bit sense what I wrote
If you look closely at the transformer on Danny's schematic and the "test ciruit 1" of Cinemag spec sheet you will see, they look the same.
Ignore the resistors on the spec sheet.
But be sure to check the phase dots. That is important especially for the tertiary winding.
So Red with the dot is the same as P1 on Danny's schematic.
GRN is P2, next green is P3, RED without dot is P4 and so on.
If you look at the picture you posted of your cinemag transformer. The lower wires are the primaries (except the blue, white and black wires).
The blue and white wire on that side correspond to P8 and P9 on Danny's schematic. The black wire is the core shield and should be connected to ground.
All the wires on the upper side are the rest of the secondaries and the tertiary windings.
It starts with white which is the white with the dot I suppose. So it would correspond with P5 on Danny's schematic.
I hope it makes at least a little bit sense what I wrote
I have some spare ready psu's if anybody needs one
Hi Im looking for info on Max Kircher transformer, identifing the pins. Im building a point to point U67, I have the tranformer , not totally sure it works tho....From looking at original schematics & lovely pictures of contstructing this with the boards I think I have the info I need, But Im not sure, and maybe theres a diagram somewhere here I have missed....can anyone confirm this is correct or otherwise....One big question ?... on my crappy drawing connection 1 & 7 on the left side of my drawing should go to either side of R18, I should get a reading on my ohm meter here ?( when resistor not connected) As its the tertary winding ? Thanks for reading.
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Jim50hertz
Well-known member
Hi all
I’ve recently replaced my MaxIO transformers with Moby BV12s and am fine tuning C17.
I looked on page one but can’t seem to find a point in the circuit to inject my signal for calibration. Can anyone point me in the right direction? What value cap for replacing the capsule during this procedure?
Also, I noticed I have MKP capacitors for C9, Will replacing these with the originally specc’ed electrolytic make any sonic difference?
I’ve recently replaced my MaxIO transformers with Moby BV12s and am fine tuning C17.
I looked on page one but can’t seem to find a point in the circuit to inject my signal for calibration. Can anyone point me in the right direction? What value cap for replacing the capsule during this procedure?
Also, I noticed I have MKP capacitors for C9, Will replacing these with the originally specc’ed electrolytic make any sonic difference?
dmp
Well-known member
Between R19 and R20 at the 'calibration 6' input
The 1963mar.pdf U67 manual describes the calibration procedure. If I recall correctly there's a typo though 1500 Hz should be 15000 Hz (see my post 218)
I don't recall the capacitance for the capsule but if you can find info on the z58 dummy head or just use a small value, like 68pf.
Lots to read on C17 here with a search.
I think most would use a film cap for C9, you'd have to listen to see if you can tell a difference with different type - I haven't tried it
The 1963mar.pdf U67 manual describes the calibration procedure. If I recall correctly there's a typo though 1500 Hz should be 15000 Hz (see my post 218)
I don't recall the capacitance for the capsule but if you can find info on the z58 dummy head or just use a small value, like 68pf.
Lots to read on C17 here with a search.
I think most would use a film cap for C9, you'd have to listen to see if you can tell a difference with different type - I haven't tried it
Jim50hertz
Well-known member
Thanks Dan, I’ll give that a whirl and see if I can’t get it calibrated to Neumann specs rather than by ear. I’ll go ahead and use a small capacitance then.
Jim50hertz
Well-known member
Another question on C9, i have a 250v cap in there just now, can I get away with a 200v cap?
Studio Mollan
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I would think so. the schematic says "Approx. 75V" so you should be fine.
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