Neumann M49 Clone : Build Thread Puck Style (TLM49 Conversion To M49 b-c)

[Murdock]

I’m not 100% sure but I think the way you mounted the torroid transformer is the culprit. I think you create a short when you have the screw which goes trough the transformer touching the case on both ends...
with Toroids you should never let the other end of the mounting screw touch the case or else the transformer shorts out and might melt.

 

[imo]

I’m not 100% sure but I think the way you mounted the torroid transformer is the culprit. I think you create a short when you have the screw which goes trough the transformer touching the case on both ends...
with Toroids you should never let the other end of the mounting screw touch the case or else the transformer shorts out and might melt.

you may be right. I tried the transformers before connecting to the board and they were fine, but possibly having a load of some sort is creating a different environment. I'll see if I can find a way to mount it on the floor of the case when i get some time

 

[Murdock]

you may be right. I tried the transformers before connecting to the board and they were fine, but possibly having a load of some sort is creating a different environment. I'll see if I can find a way to mount it on the floor of the case when i get some time

You can mount it sideways but just use an angle bracket. This is how I mount the toroids in my PSU.

 

[imo]

I’m not 100% sure but I think the way you mounted the torroid transformer is the culprit. I think you create a short when you have the screw which goes trough the transformer touching the case on both ends...
with Toroids you should never let the other end of the mounting screw touch the case or else the transformer shorts out and might melt.

Thanks for the tip. You were indeed right.
The toroid must have been shorting against the aluminum. I recut it, subbed in some 4004s and got the power supply sorted. Have B+ and H at 120 and 6. I’ll start on the mic tomorrow.

 

[imo]

Putting mic together. Thanks for the tip on the tab body! Really digging the point to point! Got Mobys transformer, had to unscrew to mount in the body, laminations fell out, and learned a quick lesson in lamination stacking.
Out of town for a couple of days and waiting on some wire, but should have her together by mid week next week.
I’m gonna build this similar to the Oliver schematic and then build a rev b with my other body down the line

 

[imo]

Curious as to how everyone is mounting tubes. The Tab guys said they use a heat resistant silicone foam that they screw down to the puck. Expensive by the sheet. Any affordable ways to get smaller amounts?

 

[Delta Sigma]

I cut some closed cell foam I use for canoe outfitting. Glued it to the PCB with E6000.

 

[egroys]

In case anyone is interested:
you can email her at [email protected]

 

[imo]

Well! I have a working mic!
I’ll post pics later.
Moby bv11, soliloqueen flat, 5840. Followed Oliver’s schematic.
Voltages spot on. Tube at 70mA
Sounds big, open, detailed but smooth on top end.

Burning in the tube.

Anybody have a reasonable source for shock mounts?

 

[terry setter]

70mA ?!?!?!?!?!?!?!?!?!?!?!?

 

[rmburrow]

70mA ?!?!?!?!?!?!?!?!?!?!?!?

Anode current through the triode connected 5840 should be like 0.7 mA...

 

[imo]

Yes. .7ma

 

[donivan]

just finished the 49c build
sounds good but having an issue with the polarity switch
8 sounds good ,card sounds good but, I get no output on omni
also if I remove the bridge on s2, I get no output
voltage at the mic
8= 116
card=57
omni=0

thanks for any help if possible

 

[dmp]

Do you have C1 connected across the capsule? Omni only works when a cap is connecting the rear to front. S2 made this an option, as it would lower the noise to disconnect this switch when in cardiod.

 

[donivan]

yes, and it reads good.
but here's one for you.
I noticed when I took the head basket off omni returned.
and as I am putting it back on, at a certain point omni goes out
it's a tight fit.
I'll look at any joints that maybe getting torqued.
I don't think it's a ground issue because the head basket shorts to the frame as soon as it touches.
it's only when it gets to a certain point on the frame rails that omni is gone.
might have to do a little metal work.
thanks for the suggestion.

 

[EarthTone]

Hey guys! I just finished my m49 and I am getting a lot of noise. Sounds good but I don't think it's usable like this. I used a Sylvania tube. Does this sound like a tube problem? Or if not, what does the problem sound like to you?

I used some NOS vintage output capacitor, Soliloqueen flat47, and Moby transformer. Here is sample around 40db of gain on the mic pre:

 

[rock soderstrom]

It is more the ocean beach sound than the frying pan, could actually be the tube. What do you have in use, 5840?
I would definitely clean the high impedance areas around the tube with 99.5% isopropanol first and if that doesn't help, then change the tube.

 

[EarthTone]

It is more the ocean beach sound than the frying pan, could actually be the tube. What do you have in use, 5840?
I would definitely clean the high impedance areas around the tube with 99.5% isopropanol first and if that doesn't help, then change the tube.

Thanks. It’s a different tube. To be honest my friend told me about these tubes, he really likes them, and asked me not to post which tube it is online. So I’m honoring his request not to share it publicly. I cleaned the board pretty well with alcohol but not the high impedance areas. Was worried about the polystyrene cap melting. I’ll try cleaning it there now. If that doesn’t help I’ll replace the tube. I have a couple more of these.

 

[donivan]

found it
rookie mistake
the assembly was too tall for the headbasket
backplate was shorting out

 

[EarthTone]

Thanks again @rock soderstrom - Just in case anyone was on pins and needles waiting for an update: I found the problem with mine! Bad tube... Switched it out and it fixed it- Extremely quiet now. And sounds great!!