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Old Component Equivalents

Discussion in 'General Electronics Discussion' started by Newtonium, Jun 20, 2013.

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  1. Newtonium


    Jun 20, 2013
    I recently got a book called 'The Radio Constructor' in which are a lot of radio-building projects. However, since this book was written in 1963 I can't find any of the parts online. Could anyone tell me the modern equivalents to:
    OC44 Transistor (PNP)
    OC45 Transistor (PNP)
    OC71 Transistor (PNP)
    Two OC72 Transistor which are a 'matched pair' :confused: (Both PNP)
    OA91 Diode
    Medium Wave Ferrite Frame
    Red Oscillator Coil
    Orange I.f. Transformer
    White I.f. Transformer
    Black I.f. Transformer
    Driver transformer type TR190/EIP
    Output transformer type TR190/EIE
    196+87pF sub-miniature twin-gang capacitor type PVC-2M :confused: :confused:
    Also, what is meant by 6V wkg after the capacitance of an electrolytic capacitor?
    Any websites where I could purchase these items would also be appreciated!
    Last question; when my book says 'Paxolin Board' does it mean one of those boards where there is copper arranged in rows on the obverse and you solder to the copper?
  2. duke37


    Jan 9, 2011
    These are the components for a single band superhet radio using germanium transistors (positive earth). The transformers colours do not mean anything without knowledge of the maker.

    You are not likely to find all the components at least at reasonable prices. You could however find an old tranny with all the components, it may even work. Try car boot sales, freecycle etc.

    The old transitors may cost pounds, modern silicon transistors will cost pence and will not need unilateralisation. It would be better to use npn transistors (negative earth).. The forum often has a thread considering replacing a germanium transistor with a silicon one.

    6V wkg means 6V working and is the maximum voltage that the electrolytic should be run at. A 10V capacitor would do.

    Paxolin board is reinforced plastic (paper, phenol formaldehyde?). The board that you want will be about 1.5mm thick but it was also made many times this thickness. It may have holes and may have copper islands or stripes. The stripy sort is often called matrix board and one of the first makers was Vero.
  3. shrtrnd


    Jan 15, 2010
    Back in '63 there just weren't that many component manufacturers.
    The numbers stump me. Does it have a page in your book that gives some kind of
    information about where you got those parts from when you built their circuits?
    Were the numbers from an electronics supply store of that era? Or might they be
    actual manufacturer's markings from some company that may have gone out of
    business long ago? My guess is, unless we've got some eighty year-old hobbyists
    on this website, those numbers aren't going to be easy to identify.
    The bright side is that there just weren't that many electronic DEVICES back then
    either, so modern-day equivalents (if you can cross them), would be ones that have
    been around for a long time.
    It doesn't look good, but good luck.
  4. Newtonium


    Jun 20, 2013

    Thank you Duke37 and shrtrnd! I was having a lot of trouble but you've helped me out a lot! I hope I'll be able to build this radio :) .
    Thanks again.
  5. BobK


    Jan 5, 2010
    Why? Why not build something using modern components?

  6. davenn

    davenn Moderator

    Sep 5, 2009
    Those OCxxx transistors will not be available any more, so you can pretty much forget about trying to buy them.
    Also the OC series transistors were Germanium, rather than silicon and just replacing them with silicon PNP's is not likely to work too well as Germanium devices had quite different operating conditions

    You really need to switch to a newer design, else you are going to end up with lots of frustrations

  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I had a couple of OC74's once (or was that OC71?)

    I should dig out a box of really old stuff I have somewhere and see if they're still there (they were salvaged from something)

    If you scraped the black paint from them they were very photo-sensitive.
  8. Newtonium


    Jun 20, 2013
    That's what I'm trying to do... I need to find modern equivalents...
  9. davenn

    davenn Moderator

    Sep 5, 2009
    But if you read what I said up the page, for the reasons I said, you cannot just put modern PNP transistors in there and expect it to work

  10. Number


    Jun 9, 2013

    Try going there for a more modern design using modern (safer?) products/components. Unless you are set on that design, I would just take a picture of the book/page and post it. We can help you find the equivalent parts. As there is still some confusion on the transformers, so or something... :rolleyes:
  11. daberbaber


    Feb 2, 2012
    If you are still interested in building your radio out of germanium equivalents, I have several older 2N types that might work. You can email me at [email protected]. Also, some have stated corrected that the silicon versions are different from the germanium types but you should at least get some reasons why they are different. In the early days (believe me when I say I was there in the 1950s) germ. devices were the only type made and they were point contact that had high noise but lower forward voltage junctions .3 to .7 for the BE junctions and a slightly smaller saturation for the CE junction. However in an analog circuit that included base biasing voltage resistors and emitter biasing resistors, these voltage differences didn't mean that much...the gain of the transistor however could and would often determine whether the next stage was forced into clipping or saturation so it was a determining value that had to be considered when cascading devices. Silicon devices were higher gain generally because of increased manufacturing techniques planar vs point contact. If you select transistors using a Hfe meter circuit you might be able to directly select devices that will function especially when you want a matched pair for the push pull output stage as I suspect these are used for. The design of early transistor radios directly followed tube designs except at lower voltages and the transistor was known as a current amplifying devices rather than a voltage amplifies devices that tubes were labeled. I hope this clears up some design concerns and please correct any of this if someone spots any errors.
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