Gotham Audio Studer C37 60HZ 1960’s

[waltzingbear]

If you examine the schematics from Studer, they give you hints on what to adjust to tweak the EQ into better alignment.
That combined with making changes to adjust for today's modern tapes (they have more hf level) can give you a chance for precise EQ.

The amplitude of low freq head bumps is defined by the construction of the head. Only some of that can be compensated for before too much tweaking has been done. (think room eq) The low frequency flatness of Studer heads is a testament to the Studer design team.

The high frequency playback response of the heads is quite good stock. Later designs from Studer used head preamps close to the head to minimize high frequency losses due to wiring capacitance. Tim deParavichi chose to add a FET at the base of the head for his designs of the 1" 2tk to buffer those capacitance's on the C-37.

Cheers
Alan

 

[RogerD]

Hi Alan,
Glad to see you post here. Dan Zellman will have the motors from Audiohouse.ch next week. Dan has done much work on the EQ and will finish it soon. IIRC he told me yesterday he split the EQ circuit. I’ll will talk to him when he starts to finish the restoration. I’m excited that it will soon be in my listening room.Thanks

 

[sigitask]

The C37 was originally owned by RCA in NYC and they tinkered with a few things. The machine uses 4 relays for NAB and CCIR and specialized EQ. All the caps are German Roderstein / Vishay, resistors are all Low Noise metal film 2%.. I am trying to keep it as stock as possible. View attachment 44935

I see there Vishay Rodestein film capacitors probably MKT. This was originally or your technician put it? Vishay bought Rodestein in 1993, and recorder was made in 1960-1967. How can it be?

 

[sigitask]

Studer C37 coming along soon to be done. I am jumping for joy! View attachment 43386

Right side switch cleaned and repaired.

I like to have advice where to buy Capstan oil DTE-EH ? Or what oil is possible to use instead this one?

 

[waltzingbear]

https://www.mobil.com/en-US/Industrial/pds/GL-XX-Mobil-DTE-Named-Series
https://www.zoro.com/search?q=mobil dte
not hard to find.

you just need to decide which is EH. EH stands for extra heavy (ISO100). Be aware that depending on which manual you look at it can be noted as medium (IS0 48 or 68) as well. In other words its not so critical, more important to lube it annually with the same series (DTE) of oil.

Cheers
Alan

 

[sigitask]

Thank you Waltzingerbear!

 

[sigitask]

Some photos of the playback preamps View attachment 44927

My C37 has absolutely different amplifiers, they using printed boards. Probably my is latest version?

 

[sigitask]

Printed board. Also in my amp they using Mullard Mustard capacitors in your Roderstein. Interesting what numbers has your amplifier?

 

[sigitask]

Also record amplifier is different

 

[waltzingbear]

Roger's machine looks to be the "early C37" as denoted in the Studer document archive.

later machines had pots for NAB and CCIR built in, at both speeds. Roger's has only the 4 pots for one EQ.

As far as I know, most of the C37's are of the circuit board variety instead of the turret assembly style.

cheers
Alan

 

[sigitask]

Im on process to restore C37 capstan block. Lover bearing steel ball, gasket was changed, bering was filled with new Mobil DTE heavy oil. But motor alone is quite noisy. Maybe there is some ball bearings to change? What cause can be?

 

[andromedaaudio]

My 2 revised B 62 studers also make a bit of noise , the telefunken is even noisier .
I think alll machines make a bit of noise .
Place the machine further from the listening position / longer cable.
Turn the music up , lol

 

[waltzingbear]

write a large check to Audiohouse and ship it off. (I take it you are in Europe?)
DTE is for the sleeve bearings only, not the ball bearings.

 

[andromedaaudio]

Im on process to restore C37 capstan block. Lover bearing steel ball, gasket was changed, bering was filled with new Mobil DTE heavy oil. But motor alone is quite noisy. Maybe there is some ball bearings to change? What cause can be?

I will listen later at the office to the noise , if you can hear a defect bearing you almost certain also have play somewhere does it turn nicely without play anywhere?.
Are the motor bearings 2 radial bearings or is there also a cup and and cone bearing which can take axial loads in the design which needs preload /and washers?
If to many washers are placed the bearing shaft doesnt turn nicely anymore..

Abec ..... is simply the american quality standard .
It doesnt make SKF or NTN bearings of less quality , those companies european /japanese only use a different standard to grade their bearings.

In my view SKF/ NTN is very good .
If you have a abec standard bearing im sure SKF can give you the correct equivalent of that .
You just need to take the housing / shaft dimensions into account off course

 

[andromedaaudio]

Lower bearing steel ball, gasket ???? I dont know what you mean, i dont hear any noise when your motor is standing nicely vertical (which will be the mounting position i assume ) , apart from you touching the housing
You mean you have noise when you place the motor horizontal ?
Bearings in appilications such as a small electric motor like in the studer usually are closed self lubricating bearings, preventing dust / moist from entering
Picture :1 bearing has a black nylon / plastic cover the other has a thin steel ring to close the bearing , self lubricating simply means grease has been put in from the factory to last a lifetime, bearings without grease or oil make noise but that speaks for itself




May be roger has a picture of what came out of his recorder so we can determine what studer put into the recorder as off factory .
I can check may be in the manual what the B62 originally had in the motor

Ps If you have no other choice you can peel off the black bearing cover and put some grease or oil manually ( clean first with degreaser ) and put the cover back , better is to change for a new bearing, the ZZ bearing with the steel closing ring you cant open , try to spray some WD 40 inside if you dont have a new one .

 

[waltzingbear]

just replacing bearings in this motor assembly will probably NOT get you a motor within spec, and may give you serious flutter problems.
This motor assembly is not a "simple" motor with just two bearings like most direct drive motors. It is an assembly of the motor, flexible coupling, and upper capstan shaft. They are all critical adjustments, that were done at the factory. The upper capstan shaft was a drop in replacement piece, but of course is long gone off the shelf.

The C37 capstan motor falls into the category of "do not try this at home"

Cheers
Alan

 

[waltzingbear]

couple photos of C37 capstan motor

 

[andromedaaudio]

Whats the lower bearing type in this design ?
Some kind of spindle trust ball bearing ?
The gentle man seems to wanna do it himself lol .
Bringing it to a good technician who is familiar with these older machines and who has all the tools is always a good idea off course.
Besides the bearing i assume coils etc need to be checked housing cleaned ....

But i must also say not all service centers do a good job im talking from expirience.

Ps if its a spindle thrust ball bearing that would explain him mentioning changing the ball and filling it with oil .
In that case i dont think its a good idea to run it in a horizontal position like he
does.
If thats the case the shaftweight is not on the ball anymore but rotates in the housing/bushing material

 

[andromedaaudio]

Capstan motor B 62 .

2 different designs for a B62 machine taken from my original B62 manual .
Not sure which is in mine
One is a ballbearing design , the other is kamm lager (german ).
.cam bearing

 

[RogerD]

My C37 is a rare bird of sorts as I have said before I think Gotham Imported only 6 U.S models. But it still has the early 1962 electronics record preamp is a C-37-C and uses mustard caps and Beyer transformers. Mine was converted by RCA for 2 EQ's NAB and CCIR.
I would defineatly send the motors off to AudioHouse. If you're in Europe it is a no brainer. Good luck.