Accuphase E-303 repair

This classic high-end Accuphase came in with reported noise on the left channel. Noise was very intermittent and only evident from a cold start. Noise was caused by excess DC voltage on the problem channel, varying from 70-300mV and only for 10-15 seconds from cold start.

Perth is a small world and one of my  FB followers recognised the amp and gave me some background on it. It was initially purchased in a very unloved state and was brought back to life by one of the best audio technicians in Perth, who I have a great deal of respect for. I was able to see exactly what had been repaired previously, to a very high standard and thus reduced diagnosis significantly.  

The amp developed this current issue months after the initial repair. This is the nature of vintage Hi-Fi, unless a full restoration is commissioned by the customer, there is a risk that other components will fail over time. A shotgun approach to replace everything is not always economically viable and we always work to the customer’s requirements and advise the options as they become apparent.

Diagnosis of the issue singled out one the transistors on the left channel power amp. The transistor would partially fail and bleed DC when cold for about 10-15 seconds. These dual PNP transistors are obsolete so I had to make my own from modern equivalent units.

These transistors are basically 2 two PNP transistors bound together in the same package. When finding equivalent replacements, it is important that the gain of each ‘half’ is matched, to reduce noise.

Binding the emitters together.