[Penthode]

The 721TS is currently running and has reached 52 hours. Running some Popeye cartoons.

I grabbed a couple of electrolytics from a rusty old Fada 630TS chassis (cabinet dissolved into shards). Looks like it was stored in a wet shed outside. So the electrolytic will have suffered wide climatic changes.

I started reforming it at 4pm today. It is now 10:30pm and at 450 volts the 10uF and 40uF capacitors in the can connected in parallel show a leakage of 200uA. This shows the capacitor is good. The 40uF measures 45uF and the 10uF measures 15uF.

I have been told I am lucky. Maybe so but I never have won a contest or even a book at the local raffle. So this baffles me why I have so much success and everyone else has horror stories to relate.

With the reformed electrolytic with such low leakage at full capacitor rated voltage, before tearing it apart, I would like to leave it at the full 450 volts for a day to see what happens. I maybe will after over voltage by say 5% to see what happens. Fortunately the failure mode is predictable: when it starts to go, like the paper capacitors, there will be a thermal runaway where the leakage increases creatingvheat which further accelerates the leakage and so on. In a paper capacitor, there is little thermal lag so the paper capacitor thermal runaway is fairly fast. The larger electrolytic thermal runaway is slower and more manageable.

Here is a picture of the reformed 630TS capacitor. Notice the VTVM reads 450 Volts DC and the Sprague TO-6 reads 200uA on the 0.6 mA full scale range. And a picture off the 721TS on the weak 10BP4.