When using an very old lens, all pictures are overexposed.
Maybe the aperture mechanism is sticky and the diaphragm blade can not close down for the metered exposure.
Test the function of the aperture by moving slightly the aperture lever on the back of the lens mount (use a small screwdriver).
If the aperture does not open and close smoothly and rapidly the there is some oily film on the diaphragms the lens has to be sent to a repair facility.
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