1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice
Dismiss Notice
This forum does not allow a single user to have more than one username. If anyone wants to change their username contact an admin and it will be done. Multiple accounts belonging to the same member will be deleted without warning.

Capacitors, a can of worms!

Discussion in 'Home Brew' started by mechanic, Sep 1, 2010.

  1. mechanic

    mechanic Well-Known Member

    Joined:
    Mar 4, 2009
    Messages:
    596
    Likes Received:
    122
    Doing replacement electrolytic capacitors in several older short wave radios and a few CBs I have come across some interesting things, mostly by accident. :pop:
    I am not fortunate to have a capacitor checker and if I suspect a rig with one or more bad caps, I replace them all. Most of the time the symptoms tell about bad caps. :headbang
    Tonight I restored a Cobra 148 GTL to working condition! No receive but good transmit with modulation.... I wanted to find out what electrolytic was causing the problem, so I replaced them one at a time and checked each new cap for the rig coming back to life. This time it was the fourth cap I replaced, a 220µf @ 10 volts. I replaced it with a smaller one in size but it is a 220µf @ 16 volts.... The radio came back to life! (y)
    Just wondering what happened I checked the cap with my Fluke DVM and compared it to another new cap. Here is what I found... Checking the new cap with the leads of the DVM in correct polarity and set in ohms scale charged up the cap, the bar meter showed a build up and then it went to about 2675 ohms and slowly fell about an ohm per second. I tried a different value new cap and it did about the same. The bad cap I pulled from the 148 did something different, not a short but the meter went to figures right away of about 60 or so ohms and slowly built up. :glare:
    So I was wondering if this is a good way of checking caps the cheap and dirty way? But the Cobra is alive!! (y)


     
  2. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    16,547
    Likes Received:
    10,201
    An analog meter is by far the better choice for checking electrolytic caps than a digital. You can see the meter swing much better than watching the numbers dance. You have the right idea about checking for good/bad but it will not give you value of course. A good cap should look like a near short for an instant and then the resistance should slowly increase as the meter is connected. A bad cap will not show a near short when the meter leads are first connected.
     

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!