A local fellow brought to the shop last weekend. He has owned the amp for a few years, used to play beautifully. Then recently it developed a bad AC hum in both channels. He had tried a few things to correct the problem, but then decided it best to bring it to me. The amp had a replacement driver board (VTA) new tubes and filter cap replacement. I do not know the age of the filter capacitor. Code printed on the label is 1116-01. After a bit of investigation I found that the installed CE manufacturing capacitor had 3 open sections. I replaced it with a F&T Authenicap, which eliminated the output hum. Then I thought it would be interesting to cut open the CE Filter & inspect the innerworkings to determine the failure. It appears that the terminals corroded and the sections failed. This is a strange failure, however if the cap is 20 years old, that could be caused by age. I routinely use CE manufacturing caps in many vintage tube amp repairs. Never had a bad one and no reports of failures from customers. This is the first I have seen fail, however with no idea of its age or possible misapplication in the past, I just consider it, another repair. I will continue to use their products.
NOTE: Follow up video showing the power supply power up sequence.    • Dynaco ST-70 Tube stereo audio amplif...