I do not get it. I have now changed out 12Q4, 12Q3, 12IC5 (MC10EL33). I have desoldered and tested 12Q5 and 12D2. All voltage rails measure ok (12 V, -12 V, 5 V, -5 V and -2.3 V)
The circuit does still not work. Scope at 12R71 and 12R72 shows a strong (1.7 V 125 MHz) clock signal with a negative offset of about 1.3 V. The signal is completely gone at 12R78. I do not understand. I mean i have changed out or checked all active devices. The resistors are also measuring ok, at least as far as it is possible to measure in circuit.
Measure point at the base of 12Q4B (pin 4) show -7 V as it is indicated in the schematic that it should be. I guess the next step would be to desolder all the passive components and replace them as well. At least the ones that are difficult to measure in circuit. Had hoped that i did not have to do this
Edit:
I measure 0 V on pin 2 and 6 of 12Q3. That surely cannot be correct ? Pin 1 and 3 measure 5 V. On pin 4 and 5 i measure the around -1.3 V signal with a strong 1V+ 125 MHz superimposed.
I also find it strange that i measure 12 V on pin 1 of 12Q4, i mean these are 11 V devices !? I could ofcource try to change out 12Q3, but i have already done it twice. However i might still try as sure does not look like it is working as it should...