DIY Studer A80 oscillator - problems with bias sine

Gentlemen, nice to meet you all.
It's my first post.
I have new but uncomplete A80 LAYBACK recorder.
With help from my friends and e-bay I found all parts - channel modules, move sensor and other.
Now machine work really fine.
But I can't find 1.080.399 Master Oscillator.
So, I made it by myself, one-side pcb from A80 manual. Other side has point-to-point wiring. It's my first "big" DIY work. I use original A101 opamps from my spare Studer boards.
It's working. But BIAS make HF noise, over 11dB higher then demagnetized tape make. It's very sad.
With oscilloscope I detect problem - after 240kHz band-pass filter sine is very good. After A101 sine have some deviations at tops and bottoms.
My friend, really good engineer, suggest: this A101 is slow for 240kHz. After replacement result was slightly different, but diviations still shown and noise still here.
Maybe Studer use special version of A101 for they oscillators? Or maybe something else? Any suggestions?
Thank you in advance,
Kirill
Sun Flower Sound studio, RU

I don't think the BW of the opamp is a problem.
Very often oscillators distort because they have too much positive feedback.
I don't have the schemo so I can't tell you what components ned to be altered.

Hi! Thanks for reply

A101 opamp - http://recordist.com/studer/A101%20latest%20version-4.pdf
Oscillator's in attachment.
Regards,
Kirill

The signal delivered by the frequency divider IC1 is a square wave. In order to turn it in a quasi sinewave, it passes through the filter constituted of L2, C9, C11 & C13. This filter produces a notch at 720kHz (the third harmonic of 240kHz) and attenuates the higher-order harmonics by ca. 40 dB.
If the notch frequency is not properly tuned, the amount of H3 will be higher than expected.
A simulation using the indicated values puts the notch frequency at 768kHz instead of 720; that seems to indicate that the actual value of the inductor may not be 2.4mH, but closer to 2.7mH.

abbey road d enfer said:

A simulation using the indicated values puts the notch frequency at 768kHz instead of 720; that seems to indicate that the actual value of the inductor may not be 2.4mH, but closer to 2.7mH.

Click to expand...

Thank you so much! Tomorrow I make new, tunable, inductor and try it...

You right, problem point is L2. It's not 2.4mH, but 2.2. Also I add 8.2mH inductor in parallel with R15, now output sine is perfect and noise come to norm.
PS: In addition I replace A101 with OPA134 and remove Q3 & Q4 - good stable result.
Thank you once again,
Kirill