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Grundig YB500 World receiver fixup and panelbeat

Discussion in 'Troubleshooting and Repair' started by bushtech, Jan 1, 2020.

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  1. bushtech

    bushtech

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    Sep 13, 2016
    While I wait for my halogen light parts to arrive I decided to give this bad boy a go. It spent most of it's life down at the coast so the rust monster has started invading.

    It still works so I want to stop further damage and give it a freshen up, volume slider scratchy etc.

    This is what it looks like inside:

    Inside 1.jpg

    There is also some battery leakage that needs sorting.

    This is what I want to sort out:

    damage1.jpg

    What is the best way to clean this up? Gentle working over with some IPA? Soapy water? If some tracks give bad continuity I will replace with wire.

    Need some sage advice here please
     
  2. Tha fios agaibh

    Tha fios agaibh

    2,075
    686
    Aug 11, 2014
    Ipa is always good served chilled, (India pale ale).

    I have cleaned circuit boards by rubbing with a pencil eraser or using baking soda and a small fine scotch bright pad.
    You will probably have to remove some components to do a decent job.

    Also try electrical cleaner solvents like no-flash.
    I would avoid the soapy water. Best to use de-ionized water to avoid conductive minerals.
     
    bushtech likes this.
  3. bushtech

    bushtech

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    Sep 13, 2016
    That sort of IPA I know well:rolleyes:

    I tried all sorts of stuff, but was a bit leery of genuine rust remover. Eventually the careful use of a machinist's scribe is proving the most successful.

    Progress so far:
    close up 1.jpg

    Most of the blue stuff, which is some sort of rust, is gone
     
    Tha fios agaibh likes this.
  4. Tha fios agaibh

    Tha fios agaibh

    2,075
    686
    Aug 11, 2014
    Nice job bushtech. Your technique seems to be working well. Even if you accidentally break a trace, you do have pictures to reference.

    I'm guessing the bluish color is the copper oxidation?

    Probably wise to replace all the electrolytic caps. One of them looks like it might be leaking.
     
    bushtech likes this.
  5. bushtech

    bushtech

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    Sep 13, 2016
    Say Wha?! 46 caps at a quick count:eek::eek:

    Yeah, probably copper oxidisation.Some of it very persistent.
    I take continuity readings every now and then just to see that I don't get too enthusiastic

    The set was working before I started so I'll take cap replacement under review.:D
     
  6. Tha fios agaibh

    Tha fios agaibh

    2,075
    686
    Aug 11, 2014
    Wow, didn't realize there was that many.
    I just saw this portion Screenshot_2020-01-02-15-38-37-1.png
    which looks to me like the caps might have lost some juce.
     
  7. bushtech

    bushtech

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    Sep 13, 2016
    Heh! Look at first photo at start of thread
     
  8. Tha fios agaibh

    Tha fios agaibh

    2,075
    686
    Aug 11, 2014
    Right. I'd at least replace e caps in the nasty area. The others are probably not long for this world due to their age.
     
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  9. bushtech

    bushtech

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    Sep 13, 2016
    I am looking at the caps in that area.However that raises some questions. This is the first time I am fooling around with something that involves radio spectrum. Looking at the caps the voltages make me wonder.
    List of voltages on caps:
    6.3V
    10
    16
    25
    35
    50
    100V
    Why on earth would somebody use a 6.3V cap? Or use that spread of voltages? Do I need to stick with that because it's a radio or can I slap in a 10Volter for the 6.3V, Or a 50V for that matter.
    Is it a matter of cost or is there another reason?
    Most of the caps are Rubycon or Hitano?. Then they suddenly use a 100uf 6.3V yellow Elna cap. Presumably they have a reason and you should sub like for like

    WTH?
     
  10. Tha fios agaibh

    Tha fios agaibh

    2,075
    686
    Aug 11, 2014
    Standard voltage ratings. As long as you meet or exceed that rating your fine.
    Higher voltage ratings are better but that can mean a physically larger caps.
    Newer caps can have higher voltage ratings than were available (comparable physical size) than years ago.
    So if you have the room to install higher voltage caps.... go for it.
     
    Martaine2005 and bushtech like this.
  11. Tha fios agaibh

    Tha fios agaibh

    2,075
    686
    Aug 11, 2014
    73sdeEdd told me the odd ball 6.3v rating is because it's a decade from other standard voltage ratings. 6.3v, 63v, 630v....

    Something to do with the manufacture process I presume.
     
    bushtech likes this.
  12. bushtech

    bushtech

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    Sep 13, 2016
    Thanks John

    On the same topic. The caps I can't ID are these with the R logo

    R cap 1.jpg

    Anybody know the Manufacturer? Cant see it in our resources section
     
  13. Tha fios agaibh

    Tha fios agaibh

    2,075
    686
    Aug 11, 2014
    I don't know.
    That R may not be a logo but some product code?

    Any marks on the other side?

    If nothing comes up.... pull it and measure its capacitance.
     
    bushtech likes this.
  14. bushtech

    bushtech

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    Sep 13, 2016
    I now suspect that they are also Rubycon's as the Rubycon's carry the same 1M numbering you see below the R. Now need to figure out if there was anything special about the Rubycon 1M series caps. Must bediscontinued as I can't find anything about them on the Rubycon site
     
  15. bertus

    bertus

    248
    79
    Nov 8, 2019
    Hello,

    I would not worry to much about the brand of the capacitors, as long as they have a good reputation.
    Rubycon, nichicon and panasonic are often used.
    I often choose the high temp (105 C) types.
    This page will tell you more about electrolytic capacitors:
    http://www.iequalscdvdt.com/Aluminum.html
    On the left of the page there is a menu to other capacitor subjects.

    Bertus
     
    bushtech likes this.
  16. bushtech

    bushtech

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    Sep 13, 2016
    Thanks Bertus, all good advice. Just wondering if they are something special like the M might stand for multilayer or something
     
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