[drakelist] R4C repair tip

[carlobianconi]

Hallo, just few words on a new ( for me ) problem on an R4C PTO not working. Checked the + 11V supply, not present. Changed C165, tantalum cap. The supply goes OK, but the pto, now oscillating, is warbling up and down in frequency on a random basis. Dismounted and changed the 8 V zener diode. Absolutely perfect! At school, 30 years ago, I learned about the fact that zener diodes are noisy devices, but this has been the very first time I experienced this . I hope that this tip will be useful to the reders! Regards Carlo Bianconi  IK4ISQ