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Thread: EE for Dummies: Basic electrical help with circuit repair?

  1. #1
    Senior Member BMWCCA's Avatar
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    EE for Dummies: Basic electrical help with circuit repair?

    With all the discussion concerning the lack of reliability in Harman electronics and concern for the environment related to recycling all these boat anchors, I decided to attempt to repair my ailing Harman/Kardon DVD22.

    A quick Google check shows similar complaints; when turning on, the power light changes color but nothing works. There's one fix involving adding a resistor but my serial number range is beyond those and supposedly has the update. Another suggests a repair to caps on the power-supply board that are listed in the repair documentation as causing other problems.

    The basic question I have, as an EE idiot is when the instructions say to measure the voltage at the pin connector . . . are we talking vDC? And does it matter what I use for the (-) for the meter? The board seems to have a common ground circuit. I assume I'm reading this with the power cord connected and the unit turned on? Carefully!

    Here's the repair manual text:

    "Complaint: Will Not Read Disc; Other Functions May Be Disabled
    See h/k service bulletins HK2004-03 and HK2005-02, as the issues covered there involve similar symptoms.

    Probable Cause: EC19 and EC20 (1000μf 16v capacitors) may be defective in the power supply. This can be checked by measuring the +3.3v and +5v voltages that are associated with EC19, 20 to see if they are low (more than 0.1v low). The SPMS output voltages are marked on the PCB adjacent to the large 13 pin header. While there is only one 3.3v pin, there are several +5v pins, and care should be taken to measure the correct one(s), which are either two +5v pins approximately in the center of the header.
    The repair performed by the owner found another blown-up cap. Mine actually has four or five that look "bulged". One writer said he used 24v caps to replace the 16v caps. Why is that an improvement if the originals are 16v?

    You can see photos of another person working on this same problem at this link: http://www.flickr.com/photos/hsp60/s...th/4353241193/

    Thanks for any assistance you can offer this capacitor novice. This a nice-sounding player for CDs using two-channel audio output. I'd be happy to see it working again.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

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    Senior Member brutal's Avatar
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    Quote Originally Posted by BMWCCA View Post
    With all the discussion concerning the lack of reliability in Harman electronics and concern for the environment related to recycling all these boat anchors, I decided to attempt to repair my ailing Harman/Kardon DVD22.

    A quick Google check shows similar complaints; when turning on, the power light changes color but nothing works. There's one fix involving adding a resistor but my serial number range is beyond those and supposedly has the update. Another suggests a repair to caps on the power-supply board that are listed in the repair documentation as causing other problems.

    The basic question I have, as an EE idiot is when the instructions say to measure the voltage at the pin connector . . . are we talking vDC? And does it matter what I use for the (-) for the meter? The board seems to have a common ground circuit. I assume I'm reading this with the power cord connected and the unit turned on? Carefully!

    Here's the repair manual text:

    The repair performed by the owner found another blown-up cap. Mine actually has four or five that look "bulged". One writer said he used 24v caps to replace the 16v caps. Why is that an improvement if the originals are 16v?

    You can see photos of another person working on this same problem at this link: http://www.flickr.com/photos/hsp60/s...th/4353241193/

    Thanks for any assistance you can offer this capacitor novice. This a nice-sounding player for CDs using two-channel audio output. I'd be happy to see it working again.
    Volts DC. Anything post rectifier is going to be DC. Either use chassis ground for the - lead, or find a black wire marked E. Use spring slip leads to prevent slippage and magic smoke release.

    I would just replace those caps regardless of the measurement if they're bulging. It appears to be a common cause of failure. If the caps voltages are under valued for the circuit or they were a bad/counterfeit batch when they get too hot from running out of spec, they'll start to vent. If they're power circuit and not in the audio path, either of these 1000uf/25V Nichicon PW or PM series power caps (105C) will work if they fit.

    PW's are a smaller physical version of the PM if available.

    http://www.mouser.com/ProductDetail/...252bceTn23Q%3d

    http://www.mouser.com/ProductDetail/...g91FDSaHutk%3d


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    Senior Member BMWCCA's Avatar
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    Thanks for clearing that up! Can't wait to get it up and running again.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

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    Senior Member DavidF's Avatar
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    Quote Originally Posted by BMWCCA View Post
    Thanks for clearing that up! Can't wait to get it up and running again.
    Take note of the polarity of the caps before removing them. They need to go back in the same way. Replacing with higher voltage spec is OK and sometimes that is what is on hand or in stock, all other specs having been addressed.
    David F
    San Jose

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    Senior Member BMWCCA's Avatar
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    Quote Originally Posted by DavidF View Post
    Take note of the polarity of the caps before removing them. They need to go back in the same way. Replacing with higher voltage spec is OK and sometimes that is what is on hand or in stock, all other specs having been addressed.
    Thanks for the help. Took me a while to come up with the caps. My local component supplier no longer handles small sales and instead told me they'd be happy to supply me with thousands, not two. So Rat Shack it was. They stocked 1000μf caps in 35v made by Lelon. Replaced two and plugged it back in leaving the 220μf cap replacement for later if needed. Everything now working like a champ. Amazing to be able to save this from the trash for $3.60 in parts and a bit of soldering.

    Thanks again! It's playing now flexing the L7s that haven't done anything important in months.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

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    Senior Member DavidF's Avatar
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    Quote Originally Posted by BMWCCA View Post
    Thanks for the help. Took me a while to come up with the caps. My local component supplier no longer handles small sales and instead told me they'd be happy to supply me with thousands, not two. So Rat Shack it was. They stocked 1000μf caps in 35v made by Lelon. Replaced two and plugged it back in leaving the 220μf cap replacement for later if needed. Everything now working like a champ. Amazing to be able to save this from the trash for $3.60 in parts and a bit of soldering.

    Thanks again! It's playing now flexing the L7s that haven't done anything important in months.
    Nice to hear. A good feeling, huh?

    For future reference I have been sourcing components from the likes of Newark, Digikey and Mouser, even for small lots.
    David F
    San Jose

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    Senior Member brutal's Avatar
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    Radio Shack is good for fuses in a pinch, and that's about it.

    The links I provided really would have been the best bet. Hell, I could have added them to my last big Mouser or Digikey order and re-shipped them out to you cheaply.

    Glad you got it running.


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    Quote Originally Posted by BMWCCA View Post
    The repair performed by the owner found another blown-up cap. Mine actually has four or five that look "bulged". One writer said he used 24v caps to replace the 16v caps. Why is that an improvement if the originals are 16v?

    It is not an improvement.

    So long as the voltage at the cap does not exceed 16 volts, raising the voltage capacity of the cap has no effect, except to make the cap physically larger (typically) requiring more space and making it harder to mount. If the voltage does exceed the 16 volt rating, the cap can explode, but then the original wouldn't have sourced a 16 volt cap here.

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    Senior Member BMWCCA's Avatar
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    Thanks, all.
    Yeah, I probably could have found better caps but then how can they possibly be worse than those used by Harman?

    I didn't "upgrade" the voltage intentionally—that was the only size RS had.

    We'll see how it fares in the next power surge from our lovely electric supplier.

    I'm kind of amazed it worked at all. Didn't really want to spend ten-bucks shipping four-dollars worth of parts only to have the repair fail. Now I know it works and I can handle it, so maybe I'll source better caps for my two-year-old-HD-TV cap repair, my next to-do-list item.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

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