Capacitor identification–old PIO?


2007-08-08 12:12 am
I have been taking apart a large old radio which was built, but never deployed, by the navy in '43 (It is a pile of rust and wishes now, got it at the scrap yard). Aside from some thordarsen transformers and chokes, good sockets and a mean looking chassis, I also found many *bolt-on* capacitors, used for coupling etc. They are mounted in a small metal rectangle with curved edges, and have large ancient solder lugs. They are labelled: "Industrial Cond. Corp. Chicago, Ill., U.S.A. CIE48703A. 600 Working Volts DC. 2x.1MFD. DO4"
Some are single caps, some are double. These are not the electrolytics for the amp, which are large cans sitting upright on the chassis. The circuit uses these for coupling, radio tuning, etc. They measure fairly well, but have around 25% drift from what was written on the "blocks". Has anyone heard of these? The values range from .01 to .1 µF. Any info would help. I'd like to know the dielectric, although I already dropped one in a guitar and it seemed to give it a much nicer tone.
I hate to say it but I am somewhat familiar with these. It gives away my age. :D These are hermetically sealed mil. spec. capacitors, and they are most likely PIO since that's about all they had back then. This type of cap doesn't age when not in use, and as long as they're not rusted and leaking, should still be good. They were an expensive part in their day too. I don't know what the tolerance was though.