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  • #10318

    Gerry O’Hara
    Keymaster

    I was recently working on a Rogers B7/30 battery set (Chassis Type 22) for a friend. The set was populated with a mix of Auto-Lite ‘Tiger’ brand and Micamold (Bakelite body) capacitors. The Micamold ones were the ‘domino’ type, so their values could be easily determined using the colour code. However, the Auto-Lite ‘Tiger’s had only part number identifiers and the schematic I have is a very poor scan with many of the values difficult to determine. Not having any information on the part numbers for this brand to hand, I was tempted to use ‘generic’ values, eg. 0.05uF for screen bypass, and using the physical size of the capacitor as a guide. However, a search on the Antique Radio Forum (ARF) turned up this posting (under a rather obscure title of ‘Purpose of 10mfd dry electrolytic positive ground’) that identified several Auto-Lite part numbers as follows, though the source of the information was not disclosed:
    Part No. Capacitance Voltage
    38102 = 0.05uF 200vw
    38105 = 0.05uF 400vw
    38106 = 0.1uF 200vw
    38107 = 0.25uF 400vw
    38108 = 0.5uF 400vw
    38121 = 0.1uF 400vw
    38128 = 0.003uF 200vw
    38133 = 0.005uF 200vw
    13533 = 10uF ?vw

    • This topic was modified 4 months, 2 weeks ago by  Gerry O'Hara.
    #10321

    Gerry O’Hara
    Keymaster

    If anyone has a more comprehensive list of the value corresponding to the Auto-Lite ‘Tiger’ capacitor part numbers it would be great if you could post it here and/or a link to a document with them in. Thanks!

    #10325

    John Greenland
    CVRS Member

    Gerry;

    Have a look here. http://pacifictv.ca/schematics/rogersb7-30data.pdf

    The chart is there for some of the values. It appears that the numbers are Roger actual part numbers.

    TTFN

    #10336

    Gerry O’Hara
    Keymaster

    Many thanks John – much better copy of the schematic.

    #10627

    Don Henschel
    CVRS Member

    I wouldn’t be too concerned with the Mica capacitors unless they are physically damaged. The exception to this is the brand or manufacturer in my British Philco 444 and I was warned that if it has a certain brand of British Mica test them all and be prepared to rip em out. Mine doesn’t have these but instead has British Philco Mica so perhaps they should be okay. Most of the Mica I have in my parts selection are the color coded Mica as well but are American or Canadian made and are usually very well made and probably a lot older than I am.

    #10842

    Gerry O’Hara
    CVRS Member

    Don, I am usually not too concerned over silvered mica capacitors (though I have come across several with ‘silvered mica disease’ which causes lightening-like loud crashes in the speaker!). However, ‘Micamold’ was an American company that produced a variety of capacitor types, including paper and silvered mica dielectric capacitors. Many of their ‘domino’ style capacitors looked like silvered mica capacitors, but were actually paper dielectric (and pretty lousy ones at that), and should always be replaced. See article here that mentions these and how to replace them (pages 8 and 9).

    #10843

    Don Henschel
    CVRS Member

    Apparently the bad ones were one particular British brand of mica made in that time period I was told by a British collector. I will have to dig through my emails and find the brand. They were not Philco which mine has. Mica and disk ceramic are the ones that usually survive unless molested or bad luck.
    These are simply “small potatoes” in my opinion to worry about including paper capacitors. A couple, yes a couple of Westinghouse 1931 WR-8 Columaire came up for sale nearby and being a sucker for punishment I tend to be, poked my nose into this area making me do some research into these socalled clock radios. OMG!! What a design using an RCA model 82 chassis with everything encased in tin boxes and cans and just for spite poured tar inside these containers as well!! Transformers and capacitors and in order to replace if required, get out the heat gun and face a stinky sticky mess. I’m still pondering to poke my nose into these radios hoping not to get burnt. One is fully functioning but at a higher price and the other has a non functional clock with a damaged face finish. The clock is bad enough but surprisingly a Repro face is available from the US for $29 plus shipping. A weird clock apparently made to work like a pendulum clock so the second hand pulses twice for every second even though it’s electric. We shall see what I’m Phoolish enough to do, a British Philco 444, a Volksempfanger, now perhaps a Columaire?

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