Folderol wrote: ↑Thu Feb 02, 2023 3:54 pmef37a wrote: ↑Thu Feb 02, 2023 3:41 pm Back in the bad old days of 'domestic' valve gear caps were often just rated for the 'working voltage' and not the peak that a fast heating rectifier slammed on them (got even worse with Selenium rects!) Nonetheless, capacitors lasted decades in most bits of kit, the exception being TVs when Silicon diodes arrived and caps blew about every 3 or 4 years.
Dave.
I have grim memories of the weird multi cap assemblies - often festooned with an unholy array of add-on ones, with some of the original terminals cut off (S/C cap) while others were just hanging across dried out ones. Then there were the copper oxide, or selenium rectifiers bodged with a silicon one bypassing them (so just one tag retained as a support, sometimes with a 10W resistor in series in an attempt to limit the surge.
Yes, there were a lot of 'cowboys' about then Will. The old B&W TVs were a special case. The main caps were rated at 275V when peak mains is nearer 340V, the cheap buggers discovered that if you stress an electrolytic several tens of volts over its rating it draws a much greater leakage current and acts as a 'free' surge limiter. The caps did not take kindly to this and failed after just a few years. Then you could get an O/C heater chain so the set never drew any HT current...BIG bang and a big mess.
Dave.