Troubleshooting simpel transistor circuit

[JOlesen]

I have an old Hohner analog synthesizer from 1969 which has a very simple analog circuit.
Never the less, it's causing me trouble.
So I hope there is someone with better electronic knowledge who can help me.
The problem is the output circuit which you can see on the attached image.
On measure point M1 there is a perfect sine wave with an amplitude of 1.8V and on M2 there is absolut nothing (a few mV, and no sine wave).
My first thought was that the transistor was shorted, so I replaced it with a new BC548, but no change.
Then I replaced the two capacitors (0,22 uF and 4uF) - but same problem.
I have measured all the resistors and they are ok.
On the collector there is 2V.
If I'm shorting the coil, the output is (offcourse) ok when the switch is in sine wave mode.
But if I switch to sawtooth mode there are no outout.
Im really frustrated that such a simple circuit is causing me trouble.
Could it be the coil? My problem is how to find a new one, because I dont know value of it.

 

[Audioguru]

The coil and the 0.22uF capacitor to ground block high frequencies but pass low frequencies. If you know the cutoff frequency then the value of the coil can be calculated but instead maybe you should simply try different values and select the one that does what you want.