My 8050 frequently gets an error 75, Format speed error

[Blacklord]

If you have already tried to readjust the RPM speed and it will not stay set or varies with temperature then this could be due to a known design problem in the 8050 circuit in that the speed determination logic diode does not meet specification. It was fairly common in the mid-80s but after 20 years these parts are no doubt much worse about leaking. There was a CBUG member fix published to field correct the problem. It involves switching CR25 and CR21 from a 1N5235 6.8v zener diode to a ECG 5014A (1N5235B) one. Follow service manual instructions for re-adjusting RPM speed.