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Antique radio repair

Discussion in 'Audio' started by Chuck Navajo1219, Mar 4, 2018.

  1. Chuck Navajo1219

    Chuck Navajo1219

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    Mar 3, 2018
    Trying to restore an American Bosch #505, as it has the best wood cabinet.
    Electronic questions regarding the Micamold capacitors.
    They appear to be electrolytic, but don't think they are, as the look like regular wax covered paper capacitors ?
    They are labeled like this ".05 .05 " mfd. Why numbered twice ?
    Also why are they metal strapped to the chassis ?
    Thank you, Chuck.
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    there are probably two .05 caps with a common lead in the package

    either for just mounting, it that is ALSO the common lead

    some photos would be really helpful so we done have to guess at what you are describing
     
    SOLARWIND likes this.
  3. Chuck Navajo1219

    Chuck Navajo1219

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    Mar 3, 2018
    Thank you. This restore is difficult for me because I have no schematic.
    If this is a double capacitor, then the common lead will be the metal mounting strap to the chassis ???
    This replacement should be easy, but there is another one in a very difficult area. Just one more question.
    Then the common lead is chassis negative ??? I ask this to retain the proper polarity when replacing.
    Thanks.
     
  4. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Micamold aren't electrolytic - as the name implies they are 'mica' and have a plastic-like casing.

    Pictures will help but specialist forums exist for these types of radio - not that I'm encouraging a loss of membership 'here' - but try over at www.vintage-radio.net/forum/index.php where they'll identify 'anything' and, most likely, either have or know where to obtain a full schematic.
     
    hevans1944 likes this.
  5. davenn

    davenn Moderator

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    Sep 5, 2009

    you didn't supply photos as I asked

    It's difficult playing the guessing game
     
  6. Chuck Navajo1219

    Chuck Navajo1219

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    Mar 3, 2018
    Sorry that I could not get a good picture to you, but you have been most helpful.
    Thank you , again.
     
  7. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Sir Chuck Navajo1219 . . . . .

    WOW ! . . . . . I just absolutely can't get any better referencing , than this, for you .
    Obtained from a Riders manual # 6 of circa 1935 vintage and being in pristine condition with these two pages never having been opened onto daylight in 83 yrs.
    Of course you'se got's to be initially somewhat Edd-ju-mucated, as you wont find a Bosch radio. You won't even find an American Bosch radio; instead, you have to fully know that they were known as United American Bosch at those early times.
    United American Bosch . . .Springfield Mass.
    https://www.bertibenis.it/images/American_Bosch/A_Bosch_1.jpg

    I done a rapid set up and shot a hi-def close up, with a Nikon D-750 . . .24meg . . .babycakes !
    That potential overkill lets me downgrade in density and definition later on .
    I used my own, one off a kind, custom made wire frame "tripod" that mounts to the front of the camera and extends out 4 tempered wires to meet at the 4 corners of a square wire frame.That end frame just rests on the opened page of a book / magazine and the weight of the frame will hold the page perfectly flattened and at a precise distance. An opaque ring flash then provides perfect, non reflective lighting.

    MICAMOLD caps . . . . .
    I have seen MICAMOLD caps in those past 83 years in almost every type possible.
    If one was molded into a .postage stamp profiled case using 6 dot color code layouts, and if the first dot was black, figure upon your having found a silver mica unit. If a silver dot, expect a paper cap in sheep's clothing.
    Also I have seen electrolytics and metal bathtub cases with mounting ground tabs and multi sections.
    Your provided info of dual 0.05 ufd units, is being a dual unit with one section providing AVC buss filtering and cathode bypassing of an IF amplifier stage.
    Since you no give pics . . .we bring pics to you:
    See which one is your unit(s) and report back, and we will fill you in.
    https://www.google.co.in/search?tbm=isch&slpassthru=1&q=" Micamold " Capacitors

    THE SCHEMATIC . . . . .


    [​IMG]

    73's de Edd
    .....
     
    kellys_eye likes this.
  8. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Your access to schematics never ceases to amaze me Edd - well done on that one especially ;)
     
  9. Chuck Navajo1219

    Chuck Navajo1219

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    Mar 3, 2018
    Thank you , 73's de Edd, for the very most information on the American Bosch. Now I have a schematic of the set and can continue with the quest to restore this antique, very good cabinet, and somewhat electrically bandaged up.
    Excellent coverage of the Micamold capacitors. I found a picture of the one that is faulty(I believe) that had puzzled me. It is a paper double .05 mfd, with a metal strap for the common lead which is soldered to the chassis.
    Best regards to a new friend in TEXAS.
     
  10. 73's de Edd

    73's de Edd

    2,726
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    Aug 21, 2015
    That image was just absolutely perfect . . .UNTIL I had to submit it to my Image hosting site and you now can see the DREADED J-peg "crusting " aberrations that were introduced upon it.
    But, had I submitted it as J-peg initially , they would STILL have to RE-J-peg it and the resultant double crusting.
    But this MUCH more quality than one would get from Nostalgia Airs schematic site.

    ASIDE . . . .
    Notice the DUDE in the factory pics frontal foreground . . . . . he's the one person that gets to operate the MEAN machine . . . the immediate others are mere nuts-bolts and rivet installers.
     
    Last edited: Mar 5, 2018
  11. Chuck Navajo1219

    Chuck Navajo1219

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    Mar 3, 2018
     
  12. Chuck Navajo1219

    Chuck Navajo1219

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    Mar 3, 2018
    Thank you for your reply and the reference to the antique radio site. I've been there and found pictures of the few old radios that I'm working on. Lots of pictures and information.
    I have four antique radios that I would like to get working again, mostly because of the various wood cabinet types( tombstone, cathedral, etc..) A Philco, Grunow, Bosch, and a Wings. The very old electronics are my most challenging job. When they do not have antennas, I'm at a loss to know what to do to get them sounding properly.
     
  13. kellys_eye

    kellys_eye

    4,281
    1,144
    Jun 25, 2010
    Most programs that generate the jpeg also allow you to set the level of compression therein - it's useful to lower the final image size (for transmission) but with a consequent loss of detail.

    If you check for this function you might have the ability to change it to a less lossy level.
     
    davenn likes this.
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