RuudNL

Telefunken M221 with defective transformer
« on: June 03, 2020, 03:46:21 PM »
I have a Telefunken M221 microphone with a defective transformer.
The problem is: how to get the old transformer out and the new transformer in...
The construction consists of a couple of plexiglass disks with the components (and the transformer) between them.
Unfortunately it is not possible to slide the transformer out sideways.
At the capsule side there are two screws, but whatever I tried, I couldn't remove them, or even turn them.
Are these very thin long screws that end at the connector side, or are there segments with both inner and outer thread that screw together?
The construction looks like: build once, service never...  ;D
Any suggestions?
There is a solution for every problem!

http://www.vansteenisaudio.nl


Gus

Re: Telefunken M221 with defective transformer
« Reply #1 on: June 03, 2020, 07:37:11 PM »
That looks like puzzle
Are the long rods the screws?
If so have you tried penetrating oil or heat at the connector end threads?

I am think you are correct about build once.
It looks like it might have been built starting from the transformer end and moving "up" soldering parts in place like cordwood construction.

EmRR

Re: Telefunken M221 with defective transformer
« Reply #2 on: June 03, 2020, 07:48:14 PM »
Paging Tim Campbell....
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

TLRT

Re: Telefunken M221 with defective transformer
« Reply #3 on: June 04, 2020, 05:47:23 AM »
I also had this mic recently, you have to start from the top and desolder ALL parts. then you can remove the disks and the transformer carefully. Then rebuild.:D Mine had a bad ac701, intermittent tuchel,and caramic disk filter cap there is no place at all to replace them(except the ac701) The hungarian m221 copies are even better as it has worse quality pcb and gefell parts.

panman

Re: Telefunken M221 with defective transformer
« Reply #4 on: June 04, 2020, 12:42:51 PM »
Those long rods are piece by piece screwed together. So, in order to get access to the trafo, you need to unscrew the two short screws on top and then as TLRT said, then unsolder everything. Wow, I never done that and I do not envy you. I wish you good luck! By the way, those are my mics on the pic. If your mic is M221 as you say, then it is the one lowest with that yellow trafo, which by the way is a Hiller T 14/1. Also marked C TM 14/1 in Hiller-mics M160 and M159. M221 was only made a very short time and a limited amount.

RuudNL

Re: Telefunken M221 with defective transformer
« Reply #5 on: June 04, 2020, 01:40:21 PM »
Thanks! I was especially interested in the mechanical construction.
I suppose this will be a time consuming (and nerve wracking) job!
There is a solution for every problem!

http://www.vansteenisaudio.nl

panman

Re: Telefunken M221 with defective transformer
« Reply #6 on: June 04, 2020, 01:59:57 PM »
I just checked out my M221 and the two top-screws are hopeless-looking rusty. Did not even dare to turn them. On M221B the screws came loose easily though.

TLRT

Re: Telefunken M221 with defective transformer
« Reply #7 on: June 04, 2020, 02:41:01 PM »
This was mine,telefunken badge m221b. it is the 120V polarization voltage version for M934b capsules.(as I know there were standard 60v versions,but never seen that). What was strange the mic is sensitive to lm317 heater regulation,it was noisy somehow,so I just build an unregulated PSU with choke.

TLRT

Re: Telefunken M221 with defective transformer
« Reply #8 on: June 04, 2020, 02:42:58 PM »
the schemo was bad in the background,there are at least 2 versions on the internet

panman

Re: Telefunken M221 with defective transformer
« Reply #9 on: June 04, 2020, 05:13:59 PM »
What was strange the mic is sensitive to lm317 heater regulation,it was noisy somehow,so I just build an unregulated PSU with choke.

Did you have a capasitor to ground before the LM317? That may be needed. My mics are M221, M221B and M155. I have three original Schoeps N20B PSUs dedicated to each. Heating in them is regulated with one zener and a choke in front of it. No noise problems. I cannot hear any difference between a PSU with or without zener, but I only ever made comparisons with Neumann PSUs. I remember at least one person say, he can hear the zener in the PSU.


TLRT

Re: Telefunken M221 with defective transformer
« Reply #10 on: June 04, 2020, 06:17:50 PM »
Did you have a capasitor to ground before the LM317? That may be needed. My mics are M221, M221B and M155. I have three original Schoeps N20B PSUs dedicated to each. Heating in them is regulated with one zener and a choke in front of it. No noise problems. I cannot hear any difference between a PSU with or without zener, but I only ever made comparisons with Neumann PSUs. I remember at least one person say, he can hear the zener in the PSU.

Yes sure it has capacitors before and after the IC regulator. Thanks for mentioning the proper type of the PSU(N20B) I'll review the schematics.

Rob Flinn

Re: Telefunken M221 with defective transformer
« Reply #11 on: June 04, 2020, 06:24:08 PM »
This may not be helpful, but when I have been servicing my old Nikon lenses if I have stuck screws I use acetone on them.  If there is any sort of thread lock used it softens it & the screws undo easily afterwards.
regards Rob

RuudNL

Re: Telefunken M221 with defective transformer
« Reply #12 on: June 05, 2020, 05:37:12 AM »
I have the impression that acetone and plexiglass might be a bad idea...
There is a solution for every problem!

http://www.vansteenisaudio.nl

panman

Re: Telefunken M221 with defective transformer
« Reply #13 on: June 05, 2020, 06:12:54 AM »
I have the impression that acetone and plexiglass might be a bad idea...

Correct.


 

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