R/E/P Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1] 2  All   Go Down

Author Topic: Neumann TLM170i dc-converter problems  (Read 11969 times)

Bo Hansén

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
  • Real Full Name: Bo Hansén
Neumann TLM170i dc-converter problems
« on: June 27, 2013, 04:16:17 PM »

I have a problem with a Neumann TLM170i, the oldest discreet built version. (not the R version with thick film circuits)
I have an fault on dc-converter board, where there is a short circuit in one winding of the small ferroxcube transformer.

I have spoken with the very helpful Martin Schneider on Neumann's forum, but there are no spare parts left to buy for this old TLM170i version.

Unfortunately I can not get hold of a schematic or winding data on ferroxcube transformer, and then it becomes difficult to make a new one.

Is there anyone here who have solved similar problems with dc-converter board, and figured out how this transformer is built in its winding structure.

Maybe someone even has a dc-converter card or transformer for sale as a spare.

Dare I ask if anyone has a schematic of the TLM170i version, maybe someone has re-drawn the electronics on their own.
(sorry, but I have to ask)

Best from
Bo
Logged
Hansén Audio
Gothenburg, Sweden
www.hansenaudio.se

klaus

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2210
Transformer Sources
« Reply #1 on: June 28, 2013, 03:00:31 AM »

Hello Bo,
 I am sure Neumann's Uwe Sattler will read this, and may have a suggestion. If worst comes to worst, I can also contact Oliver Archut (a renown transformer manufacturer) for his opinion.

Hang tight!
Logged
Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Bo Hansén

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
  • Real Full Name: Bo Hansén
Re: Neumann TLM170i dc-converter problems
« Reply #2 on: June 28, 2013, 06:33:15 AM »

Thanks Klaus,

I'll wait and see if something comes up suggestions here.

Better than this forum regarding similar problems are probably hard to find.

-- Bo
Logged
Hansén Audio
Gothenburg, Sweden
www.hansenaudio.se

Jim Williams

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 599
Re: Neumann TLM170i dc-converter problems
« Reply #3 on: June 28, 2013, 11:52:32 AM »

Cross the specs (if you find them) with the coils from AKG, readily available. Perhaps you can use a 414 or 460B transformer coil to do this. You may need to adjust a resistor or cap value but I'm pretty sure it can be worked out, it's only a DC converter. An examination of the surrounding circuit should make that achievable.
Logged

Uwe

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 68
Re: Neumann TLM170i dc-converter problems
« Reply #4 on: June 28, 2013, 12:25:49 PM »

Replacement transformers for the DC/DC converter of Neumann's TLM170 were never available, only the complete printed circuit board (part # 853400368x - with the last digit identifying one of at least 3 slightly different versions). By the way, I have never seen any of these transformers defective, occasionally I encountered faulty transistors, FETs, diodes, the CMOS quad-NOR gate or a capacitor. However, over 20 years after the original version of TLM170 was succeeded by the TLM170R, original replacement boards are no longer available. The 'old' version could be upgraded to the current TLM170R version, but for technical reasons of incompatibility, this would require replacement of all three boards: DC/DC converter, amplifier, and AF output with RF filters.

Please request a quote from:

Sennheiser Nordic (Sweden)
Vretenvägen 10
171 54 Solna
Sweden
Tel.: +46 (0) 8400 504 00
Fax.: +46 (0) 8400 504 01
E-mail: [email protected]
www.sennheisernordic.com

or from the Service Department at Neumann|Berlin.

There may be other ways to restore this microphone. The obvious solution, if you could find one, replacement of the DC/DC converter board (unlikely), or if indeed the transformer is defective, reverse engineering it by carefully documenting its dis-assembly and unwinding all six sections, some of which may be bifilar. That means keeping track of the wire diameter number and direction of turns, as well as the exact correlation of all 12 connections in their proper phase to their designation on the board. (Another good reason why replacement transformers were never made available.)

Good luck!
Logged

Bo Hansén

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
  • Real Full Name: Bo Hansén
Re: Neumann TLM170i dc-converter problems
« Reply #5 on: June 28, 2013, 05:57:34 PM »

Uwe,

Thanks for your reply.
Klaus was right, he thought you would read this and maybe have a few suggestions to my problem.

I'm also very grateful that you attached schematic, now I understand the design structure much better.

The problem is short to ground in the coil that is connected to 0.33 uF and BC550 collector.

Unfortunately, the attached schematic is so small and indistinct, so now I can only guess that the transistor BC550 as I have been tracking, is a form of a voltage regulator and the other end of the coil goes to a MOSFET transistor source leg to ground.

It is suspicious that there is a short circuit in this MOSFET transistor, when I look at the schematic.

However, among the first things I did was to measure all transistors, and I found nothing strange then.

But to not make a fool of myself here on the forum, I will go to the workshop tomorrow and double check this MOSFET transistor.

I should be more than happy to finally get a small glance into schematic for TLM170i as you so kindly enclosed here, but it is possible to tempt fate and ask for a PDF file, so I can more clearly read component values ​​and how the connection is made.

Btw,
I got a quote for TLM170R exchange cards from Neumann in Berlin, and all three cards together cost 1089 Euros.
This together with my cost of work will be a hefty penny for the customer in the end.
For that reason, I must give it a chance to find the fault on the original dc converter card.

Thanks Jim, that's a good thought.
I thought myself possibly looking at microphones that have other solutions to make many positive and negative polarization voltages, such U87Ai or U89.
But there is a lot of work and modifications to use U89 dc converter card in the TLM170, and it may not be possible.

--Bo
Logged
Hansén Audio
Gothenburg, Sweden
www.hansenaudio.se

Jim Williams

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 599
Re: Neumann TLM170i dc-converter problems
« Reply #6 on: June 29, 2013, 12:19:11 PM »

I would swap out those transistors, they are cheap. If the coil is still an open circuit, perhaps a careful re-soldering of the pins will re-connect that coil. Sometimes the coil wire insulation isn't completely removed and you might have an ittermitant connection to the pin. A meter should sort that out.

A last resort (besides completely changing the pcb's and mic sound with the re-designed newer surface mount cards) would be to suss out the available voltages and commit to one or two patterns.

I liked the original TLM170's, the later versions lost something. You can hear a 1980's model on Vannesa William's first release, "The Right Stuff".
Logged

Bo Hansén

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
  • Real Full Name: Bo Hansén
Re: Neumann TLM170i dc-converter problems
« Reply #7 on: June 29, 2013, 05:27:51 PM »

Life becomes much easier with a schematic.
Uwe, thanks for that.

I picked out and measured the MOSFET transistor more thoroughly this time.

It turned out that I at first measurement misled me on the built-in protective diode between drain and source, as I suspected was there.

But I found out now that the transistor has a bit conductivity in the other direction too.

Probably there is something more wrong that may have caused this, so I will not shout hurray yet.

The problem now is to find a suitable MOSFET.
This orginal transistor on the card is a Siliconix with an industry code: 6300 (8207)
It is a N-channel small signal in TO-237 case with a small metal tab.

I will try with BS107 in TO-92 case which is a standard small-signal N-channel MOSFET. (these I have in stock)
200V, 250mA, 350 mW.

I'm sure Uwe have a suggestions, but also Jim tends to be very clever to replace semiconductors.

Jim, Interesting observation regarding the difference between the old and new version.
I will ask my client if he reflected on the difference, he has some of each type.
Btw, you mention Vannesa William's, do you have any family connections ?

--Bo
Logged
Hansén Audio
Gothenburg, Sweden
www.hansenaudio.se

klaus

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2210
Re: Neumann TLM170i dc-converter problems
« Reply #8 on: June 29, 2013, 05:40:38 PM »

Boy, this is getting deep! Can we keep the discussion on a level that is comprehensible for the majority of readers?

Logged
Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Bo Hansén

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
  • Real Full Name: Bo Hansén
Re: Neumann TLM170i dc-converter problems
« Reply #9 on: June 29, 2013, 06:02:50 PM »

Sorry Klaus,

I was so excited when you kind people gave me help.

Shall calm me down a few kilohms.

--Bo
Logged
Hansén Audio
Gothenburg, Sweden
www.hansenaudio.se

Bo Hansén

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
  • Real Full Name: Bo Hansén
Re: Neumann TLM170i dc-converter problems
« Reply #10 on: July 03, 2013, 08:02:50 PM »

Just want to report the results after the change of the MOSFET transistor.

Sure, it worked brilliantly with BS170 transistor and the dc-converter started and worked as it should.
So there was nothing wrong with the small ferroxcube transformer as I first thought.

After this I changed all electrolytes and tantalum capacitors on both dc-converter and amplifier card, and also dry cleaned capsule diaphragm.

Now it sounds and works perfectly again.

Thanks for your help and a good conversiation.

Best from
Bo
Logged
Hansén Audio
Gothenburg, Sweden
www.hansenaudio.se

Jim Williams

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 599
Re: Neumann TLM170i dc-converter problems
« Reply #11 on: July 04, 2013, 12:55:24 PM »

Jim, Btw, you mention Vannesa William's, do you have any family connections ?

--Bo

Sorry, that gave me a laugh. If there are any familial connections, it would be one of my ancestral slave owning relatives, one of those 'Williams' we don't talk about much these days. Then there's that Cherokee "affair" that's also is hidden in mystery. Got to love your relatives!

Someone once wisely said, "You can pick your friends but you can't pick your family". Probably P.T Barnum or one of the Kardashians.
Logged

Bo Hansén

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
  • Real Full Name: Bo Hansén
Re: Neumann TLM170i dc-converter problems
« Reply #12 on: July 04, 2013, 03:25:34 PM »

Quote
Sorry Klaus,
I know you are thinking .....
Discuss NOT other irrelevant things than microphones here on the forum.
You must be a mind reader.
Logged
Hansén Audio
Gothenburg, Sweden
www.hansenaudio.se

Bo Hansén

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
  • Real Full Name: Bo Hansén
Re: Neumann TLM170i dc-converter problems
« Reply #13 on: July 04, 2013, 09:40:54 PM »

Klaus Heyne,

Although you are the moderator of this forum, so I do not appreciate that you visit my post in this thread and delete parts of my text.
Especially as it was addressed to Jim Williams and not to you.

Best regards
Bo Hansén
Logged
Hansén Audio
Gothenburg, Sweden
www.hansenaudio.se

klaus

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2210
Re: Neumann TLM170i dc-converter problems
« Reply #14 on: July 05, 2013, 03:07:12 AM »

Part of your off-topic post about "Vanessa Williams" was erased due to a software glitch that replaces poster's responses with those of the moderator- see  explanation on Page 2, a couple of posts below this one.

Next time, please send a PM when you want to chat about off-topic issues like familial relationships between posters and celebrities.

If getting you a quick response to your original question from a Neumann representative (and an up-to-now unpublished schematic!) does not meet your expectations, please try another venue.
Logged
Klaus Heyne
German Masterworks®
www.GermanMasterworks.com
Pages: [1] 2  All   Go Up
 



Site Hosted By Ashdown Technologies, Inc.

Page created in 0.133 seconds with 21 queries.