Hi, thank you for your advice.
I’ve already measured the IC3, got following measurements:
- leg 1 = 6.06V
- leg 2 = 5.4V
- leg3 = 1.27V
- leg 4 = 5V
- leg 5 = 7.75V
- leg 6 = 6.77V
- leg 7 = 7.35V
- leg 8 = 8.56V
so quite close to the service manual.
I did replace most of the tantalum capacitors as well (all but 2.2µF 35V, they were not in stock unfortunately)
Unfortunately I don’t have a frequency meter, just a multimeter (also not the best one)
I will check the transistor voltage tomorrow.
What I did as a temporary fix – I installed 50kOhm potentiometers, so I have wider adjustment range for the speed. With this I was able to drop the speed to correct values, but the W/F is still around 1% (measured with RPM app on iOS) which is of course not great.
And also I don’t like using not spec parts and would love to find the actual reason for this behavior and not just apply bandaid on it.
