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Thread: Hello! I got a machine that was sold for parts! May need assistance?

  1. #51

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    I found a ruler. I took some measurements. Are these numbers possible, or am I missing something? the Caps appear to be 5mm diameter by 15mm tall? The space between the pins on the back of the board looks really close, maybe 2mm? Do these numbers seem like they could be accurate? I really need to get myself a set of digital calipers.

  2. #52

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    Okay.. I am getting ready to put in an order for some parts from Mouser, and I have come across suggestions for Caps from several places, and I am uncertain of which type to get. They have Nichicon 22uf25V UKT line that matches the values of the caps on the board and then there is Rubycon 22uf25V caps as well. They are both 5mmx10mm with 2mm spacing for the pins. I have heard that the Nichicon ones are suggested for Audio systems, and the Rubycon were recommended by a place that repairs motherboards. Is there any difference really between the two? They both match in the specs listed on the details section, but is there a reason why I should buy one over the other? Also, I have some Dallas RTC modules I need to replace. Aside from the difference in the built in storage between the A and C models, is there a difference between getting the 12887+ and the 12887A+ Thank you for the assistance and advice. I appreciate it.

    Regards,

    Nathan

  3. #53
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    Quote Originally Posted by Nathanieltolb331 View Post
    I found a ruler. I took some measurements. Are these numbers possible, or am I missing something? the Caps appear to be 5mm diameter by 15mm tall? The space between the pins on the back of the board looks really close, maybe 2mm? Do these numbers seem like they could be accurate? I really need to get myself a set of digital calipers.
    The numbers I gave are examples of common types I usually see, but they can come in other sizes as well. If you measured 5x15, then you can look for those dimensions. You can also substitute another size if you think the other size will fit, which you may have to do if you can't find an exact matching size. I often have to substitute capacitor sizes because capacitor technology has come a long way in the past 30 years. 20 and 30 year old capacitors are often larger than their modern counterparts for the same capacitance and voltage rating.

    Quote Originally Posted by Nathanieltolb331 View Post
    Okay.. I am getting ready to put in an order for some parts from Mouser, and I have come across suggestions for Caps from several places, and I am uncertain of which type to get. They have Nichicon 22uf25V UKT line that matches the values of the caps on the board and then there is Rubycon 22uf25V caps as well. They are both 5mmx10mm with 2mm spacing for the pins. I have heard that the Nichicon ones are suggested for Audio systems, and the Rubycon were recommended by a place that repairs motherboards. Is there any difference really between the two?
    You'll generally want to find the lowest impedance and/or lowest ESR value caps with the highest temp rating and longest rated life. Mouser will show these numbers in their parts lookup system. Nichicon and Rubycon capacitors are fine, as are most of the other brands on Mouser. The only one I'd stay away from is United Chemi-con, they've had several junk capacitor series in the past like KZG and KZE series.

    You don't really need audio grade capacitors if the capacitor isn't being used for audio.


    [/QUOTE]I have some Dallas RTC modules I need to replace. Aside from the difference in the built in storage between the A and C models, is there a difference between getting the 12887+ and the 12887A+ Thank you for the assistance and advice. I appreciate it.[/QUOTE]

    It's really better to just fix the existing Dallas chips. Places that have those DS12xx7 chips often have new-old stock, and the batteries in those chips can be just as dead as the one you currently have. It's not terribly difficult to rework an existing chip, you just need a dremel with a small cutter tip to grind into the packaging.

    http://www.mcamafia.de/mcapage0/dsrework.htm
    https://www.youtube.com/watch?v=NdlSfqto_0o

  4. #54

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    Quote Originally Posted by GiGaBiTe View Post
    It's really better to just fix the existing Dallas chips. Places that have those DS12xx7 chips often have new-old stock, and the batteries in those chips can be just as dead as the one you currently have. It's not terribly difficult to rework an existing chip, you just need a dremel with a small cutter tip to grind into the packaging.

    http://www.mcamafia.de/mcapage0/dsrework.htm
    https://www.youtube.com/watch?v=NdlSfqto_0o
    The DS12887+ and A+ chips I was looking at were on Mouser.com. I was buying them new I thought. Are they old stock as well? Hmm. I did not know that. The only difference between the Nichicon and the Rubycon caps that I can see from their information is their size, both are 5mm by something the Rubycon are 7mm tall, and the Nichicon are 10mm tall. The Rubycon are slightly more expensive, by I think a penny? I don't see anything labeled as ESR or Impedance in the specifications? I see Tolerance, Ripple Current, Max and Min Operating temps, size, Qualification, and something called Dissipation Factor? Is ESR the Tolerance percent? Both caps have 20%, is that good enough for recapping a motherboard?

  5. #55

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    Quote Originally Posted by Nathanieltolb331 View Post
    I don't see anything labeled as ESR or Impedance in the specifications? I see Tolerance, Ripple Current, Max and Min Operating temps, size, Qualification, and something called Dissipation Factor? Is ESR the Tolerance percent?
    No, it's equivalent series resistance.

    https://en.wikipedia.org/wiki/Equiva...ies_resistance
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  6. #56
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    Quote Originally Posted by Nathanieltolb331 View Post
    The DS12887+ and A+ chips I was looking at were on Mouser.com. I was buying them new I thought. Are they old stock as well? Hmm. I did not know that.
    Many places that stock that chip often have years or decades old stock, hence "new-old stock". Dallas Semiconductor has been defunct since 2001, being bought out by Maxim Integrated. Anything that uses the Dallas Semiconductor logo is going to be at least 19 years old, unless Maxim retained the old Dallas name for products they still manufacture. Even with how little current these RTC chips use, ~20 years is getting long in the tooth for the tiny button cell batteries potted in the modules.

    Quote Originally Posted by Nathanieltolb331 View Post
    I don't see anything labeled as ESR or Impedance in the specifications?
    Mouser has filters for low ESR capacitors, and provide datasheets for all products. The impedance is usually specified, but ESR is hit or miss. Using a general purpose capacitor usually won't cause any issues, but you don't want a crappy capacitor like those Chinese Ebay specials which have astronomical impedance and ESR. Generally, the smaller the capacitor is, the higher the ESR and impedance will be. Good capacitor brands will engineer the capacitor to have the lowest possible of both, while balancing other performance characteristics, but the Chinese junk will just build the capacitor as cheaply as possible so that it has the rated capacitance and voltage, but toss everything else out.

  7. #57

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    I found these, they are low impedance, will they work? - https://www.mouser.com/ProductDetail/647-UPS1E220MDD1TA
    Also, from what I am being told here and a couple of other places, even these Maxim based DS12**** chips are NOS and so there is a serious chance that the batteries are flat already? - https://www.mouser.com/ProductDetail/700-DS12887

    So if I understand correctly, low impedance and low ESR are two different things? I just want to make sure I am understanding things correctly. I wish I had more experience with these things when I was younger. I find all of this extremely fascinating, but I worry that I cannot get enough experience under me now to be effective at repairs and understanding everything now.

  8. #58

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    Quote Originally Posted by Nathanieltolb331 View Post
    I found these, they are low impedance, will they work? - https://www.mouser.com/ProductDetail/647-UPS1E220MDD1TA
    Also, from what I am being told here and a couple of other places, even these Maxim based DS12**** chips are NOS and so there is a serious chance that the batteries are flat already? - https://www.mouser.com/ProductDetail/700-DS12887
    Mouser is pretty reputable. It's unlikely they would sell NOS anything without stating so on the page....

  9. #59
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    Quote Originally Posted by Nathanieltolb331 View Post
    I found these, they are low impedance, will they work? - https://www.mouser.com/ProductDetail/647-UPS1E220MDD1TA
    Those are fine.

    Quote Originally Posted by Nathanieltolb331 View Post
    Also, from what I am being told here and a couple of other places, even these Maxim based DS12**** chips are NOS and so there is a serious chance that the batteries are flat already? - https://www.mouser.com/ProductDetail/700-DS12887
    Looks like Maxim may be still manufacturing Dallas Semiconductor parts, so these may be new. I would still try to rework the existing chips if possible, since the only thing wrong with them would be a dead battery.

    Quote Originally Posted by Nathanieltolb331 View Post
    So if I understand correctly, low impedance and low ESR are two different things? I just want to make sure I am understanding things correctly.
    Impedance is the resistance to AC current flow in a circuit, ESR is the equivalent series resistance of a capacitor in a circuit. The ideal capacitor would be lossless, since the anode and cathode are not directly connected; But due to physics, they have various parasitic qualities that must be known and addressed.

    https://www.mouser.com/pdfDocs/nichi...hite-paper.pdf

  10. #60

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    Quote Originally Posted by GiGaBiTe View Post
    Impedance is the resistance to AC current flow in a circuit, ESR is the equivalent series resistance of a capacitor in a circuit. The ideal capacitor would be lossless, since the anode and cathode are not directly connected; But due to physics, they have various parasitic qualities that must be known and addressed.
    Thank you for the information. I really wish I had taken electronic engineering and soldering classes when I was in college, but since they weren't needed for my degree, I stuck to the courses I needed so I could graduate faster. If I could go back and change that, I would. I have a massive manual about electronics, but I feel like I need the electronics for dummies book, which I thought I had, but apparently don't. I will be putting in an order tomorrow for the caps, since they have a 4 week lead time. I will order one DS12887 chip for now, because I have a machine I want to get up and running immediately, and I will try and follow a guide on opening up a dead RTC and see if I can wire in a new battery. Thank you to everyone for the information. I will post again when I get the caps and re-cap the board. Here's hoping it works. Would really like to save another machine. I saved the other packard bell I got, just need to see if there is any way to repair the CD-ROM drive, because it uses the different drive interface than IDE.

    Thank you again!

    Regards,

    Nathan

    -Edit- Oh, and I will create posts for the two other machines I need to do the RTC stuff on for when I need help with those .

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