Telefunken M15 schematics and info needed

[Kingston]

Hi,

I can't seem to find schematics for this massive workshorse 1/4" two track unit. I found a brochure from http://www.audiosharing.com/archive/german_audio/telefunken/telefunken.htm with some basic info.

The problem is this. It seems to be impossible to drive the tape into any kind of audible saturation (configured to 15 ips now). It's very transparent - originally a broadcast recorder - and no matter what I do, the internal gain staging doesn't seem to provide enough input level to tape. I could drive it externally with some line amps, but then I would be just saturating the input transformers, when it's tape saturation I want.

Maybe schemas will tell me what can be done.

Disclaimer,
the only point for using a clunky machine like this at this day and age is to use it as a saturation effect, and I'd like it to be a bit more pronounced.

 

[peterh]

Hi Kingston,

no, no, do not modify the Amps of the M15. It would be a sin The machine is designed to produce the best recording that was possible those days (and even now). Saturation and distortion is something that had to be avoided and the circuits are designed to do so. The designer never even dreamed that the M15 would be used as a effect device. I guess you better take a software plugin or a semipro unit to get the saturated sound effect, but leave the M15 as it is.
I am pretty sure, that M15 (as well as Studers, et. al) will become as sought-after as Neumann/Schoeps/etc Tube mics are today, prices will increase.... My M15a (even without dolby) makes far better recordings, than any digital device i have ever heard.
There is one hint i can give you: try to get a tube version of the Telefunken M5.

If you really want to go ahead, pls let me know, for which Amp you need documents for.  The complete Docs are several folders with a lot of A3 drawings..

Cheers,
          Peter

 

[Kingston]

I'm not really looking to do any major destructive mods. But something like 6-12dB more level from the input to tape. I'm not familiar with this machines input amp topology and gain staging at all. Maybe it already has some trimmers to achieve this? Maybe I can already do this externally somehow, without over-driving the input?

This is the kind of info I'm interested in.


PS. I highly doubt these will ever become collectors items. They are as big as washing machines, with difficult calibration procedures and quality tape media itself is becoming increasingly difficult to find. This stuff will simply die away sooner or later, which is a shame.

 

[audiox]

I have worked with Telefunken M15/M15A machines long time ago. A few warnings: The documentation is not very illustrative and many schematics are drawn idiotically (the way that it is very difficult to get an overview). There is a huge difference when compared with Studer docs (with Studer you need 10 minutes of reading the manual and then you know exactly what to do).

M15 basic adjustments are relatively easy to do but if you need to repair something, days or even weeks of studying of the manuals is required.

By the way, spare parts are still available:
http://www.hilpert-audio.de/

 

[living sounds]

I've got an M15 and I can easily drive it into saturation. The preamps won't mind, they have lots of headroom, but the tape saturates very well (driven by a +4db converter via balanced connections), no need for any modifications, you just need to calibrate it properly. I'm using SM911 tape if that's any help. I

 

[Junction]

I have an M15A 24 track machine and manual with schematics, if there is any info you need from the manual let me know.

Michael

 

[RayBlack]

Hi guys,

as there are some folks here knowing quite a lot about tape machines, perhaps you can help me out here.

I was originally looking to buy a M15A Recorder, cause I heard about the high headroom of the Input stages
and the ability to drive the tape saturation like that. I'm looking for that slightly compressed sound of the 50ies,
they got through driving the tape hard. I know that there was a lot going on in those NFB Tube Amps, but that will be the second step.

Now a guy offered me a M21 and a M21R machine, from which the M21 is complete. The M21R is missing an input stage, which
was built in the M21, but the motor and psu of the M21 is totally fine. The M21 has slight speed fluctuation, which I'm
hoping to get fixed with the parts of the M21R or replacing dried out caps. (any clue where to start?)
The price for all this stuff, including M21,M21R and two wagons shall be 200€, which is a nice price I think.

Now the 64$ question: Is the M21 going to give me a similar sound to the M15A, when driven with high volume ? (Input stages have the same headroom of +24dBm)

It's full of ICs and thats why I'm quite unsure about it. But otherwise its the last tape recorder built by telefunken/aeg
so it's highly developed in many ways.

Perhaps it could be easily checked, by recording something on it, with high volume and replaying it to check the saturation.


What do you guys think ? Ever used one like that ?

Pics can be seen here:
M21

M21R

Greets
Ray

 

[abbey road d enfer]

I'm not really looking to do any major destructive mods. But something like 6-12dB more level from the input to tape. I'm not familiar with this machines input amp topology and gain staging at all. Maybe it already has some trimmers to achieve this? Maybe I can already do this externally somehow, without over-driving the input?

What source are you using to drive it? I reckon you need at least +10 dBu input to make this machine grit. In my experience it was easy to induce tape saturation without a hint of electronic saturation. Is the machine performing up to specs?

 

[jensenmann]

If OP bought his machine from german broadcast chances are high, that the inputs are padded 4dB down. They´ve been using external NR for gainmakeup at that time to avoid tape saturation.

 

[Kingston]

Is the machine performing up to specs?

I don't know, and I suspect there indeed was a broadcast standard type pad as suggested by jensenmann, knowing where the machine came from. I passed the opportunity to acquire the unit due to the fact there was no schematic or calibration tape available. Pretty mandatory stuff since I didn't intend to run the machine by luck alone.

 

[audiox]

I passed the opportunity to acquire the unit due to the fact there was no schematic ...

I am quite sure that I have the M15A service manual in my garage. It is more than thousand pages, so please don't ask me to scan it and e-mail to you.

But if you need schematic for one or two cards, I can borrow digital camera from my friend and take some photos.

 

[tmuikku]

I passed the opportunity to acquire the unit due to the fact there was no schematic ...

I am quite sure that I have the M15A service manual in my garage. It is more than thousand pages, so please don't ask me to scan it and e-mail to you.

But if you need schematic for one or two cards, I can borrow digital camera from my friend and take some photos.

Ugh, thousand pages :-[ I've got m15a waiting for refurbishing, too. I requested service manual from Hilpert audio 6 months ago and they said it is being digitized. Page count may be the reason it is still not available

 

[Kingston]

It is more than thousand pages

damn! How complicated can a tape machine be?

Is it one of those thorough military type manuals where they not only teach you electronics theory, but also how to properly dispense a working unit with explosives in case of quick retreat?  

 

[audiox]

Is it one of those thorough military type manuals where they not only teach you electronics theory, but also how to properly dispense a working unit with explosives in case of quick retreat? 

No. You must be an expert in electronics and tape recorders to understand it. Nothing explained. It is just made by people who love to document every little detail they can. Not very user friendly approach.

There are actually two binders (two thousand pages). I think this is some kind of factory master manual.

 

[EEMO1]

I got 2 of these babies in my studio. no manual though...

Im willing to chip in for some euros if I can get a copy. I got an impression that you can still service these by AEG?

 

[audiox]

I got an impression that you can still service these by AEG?

AEG Telefunken has not been in the tape recorder business for a long time. As I said a few posts earlier, check this:
http://www.hilpert-audio.de

 

[tmuikku]

I finally cleaned one and it seems to work fine without a tape (I don't have any tape yet ). Does anyone happen to have notes for m15a adjustment? I've got no clue what each trimmer does on each amp / logic card... Also I'm about to order some tape, calibration tape and a demagnetizer. Is there any source where I could get em all? Canford sells MRL calibration tapes in EU, but I'm not sure if they carry any fresh tape or demagnetizers.

 

[andre tchmil]

I know someone who has two M15 stocked.
He wants to part with them but has no clue how much they are worth.
any idea of an average price?
They come in the big trolley.

 

[andre tchmil]

I know someone who has two M15 stocked.
He wants to part with them but has no clue how much they are worth.
any idea of an average price?
They come in the big trolley.

anyone ?

 

[tmuikku]

I know someone who has two M15 stocked.
He wants to part with them but has no clue how much they are worth.
any idea of an average price?
They come in the big trolley.

anyone ?

Hi there!

Hilpert has repaired units with new heads on sale. ~1700e 1/4", and ~4000e 1/2" with 30ips
http://www.hilpert-audio.de/audio/index_e.php?site=geraete&inhalt=geraete/e_geraete_aeg_m15.htm

These cost from zero to couple hundred in questionable shape in Finland. Most often they are salvaged units with poor maintenance history since YLE ( Finnish broadcasting company ) got rid of them some ten years ago.


Hope this helps! Try to see if there is any sold on eBay to get some questimate!