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ID Obsolete Motorola Communications Capacitors?

Discussion in 'Datasheets, Manuals and Component Identification' started by shrtrnd, Mar 21, 2017.

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  1. shrtrnd


    Jan 15, 2010
    I bought a big bag of Motorola Communications capacitors over the weekend, erroneously thinking I'd be able to Google the part number. No luck doing that. Does anybody know where I can get the capacitance and working voltage values of Motorola capacitor part # 48C83159B01? Axial leaded electrolytics.
    Thanks for trying in advance.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    A photo with something for scale might help.

    The capacitance you can get by measuring them.

    The voltage you could estimate based on the approximate date on manufacture, the side, and the capacitance.

    It's possible that after measuring the capacitance of a few, some part of the part number will match. They could be 48uF, and some other par is the code voltage (not very useful) or they might be 1uF and 48V.

    If they're really old you'll have to re-form them. This involves charging them with a series resistor and a meter across reading the voltage, and a meter in series measuring the current. If they need reforming, the first time you charge them they will have quite high leakage, but this will reduce on subsequent charges. This generally exhibits itself as faster and faster charge times.

    Re-forming should be done with the capacitor in an acrylic box or something similar that allows you to see any venting but also protects you from an explosion.

    If you have a lot of these capacitors then you can charge one up to higher and higher voltages until it vents or explodes. Let's say it does that at 60V.

    The next one of charge to 1/4 of this voltage and immediately discharge it (do this through a resistor which will charge it in about 5 seconds. For capacitance C in uF, time T, and voltage V, the resistance in ohms should be 1,000,000/C and the power rating about V*V/R.

    Let's assume they're 1uF and the first one vented as 60V. The resistor should be 1MΩ, and the power 120*120/1000000 = 0.015W. That's tiny. Use a 1/4 W or 1/2 W or whatever you can find. For bigger capacitors the wattage will be higher.

    Now connect a volt meter across the capacitor, and use the 1M resistor to discharge the capacitor if it has any significant charge on it. Charge it from a 15V source and check the voltage after 5 seconds. It should read 99.3% of your source voltage. Anything less may be due to leakage, or errors in your resistance, capacitance, or voltage measurements. Discharge the capacitor again (until the voltage is below 1% of your test voltage). Then charge it again and read the voltage at the 5 second point. Is it higher? If so leakage is reduced and the cap is re forming. Repeat this process a few times, or at least until you observe no further improvement.

    Repeat this process by first doubling the voltage, and then by going in increments of about 20% of the voltage the cap vented at (in this case 10 volts would be fine). In this case the voltages would go 15,30,40, 50, 60, 70,... Measure the capacitance after each test. If it has risen, then your time to charge is now the new capacitance * 5 / the old capacitance ( so if it goes from 1 to 1.2uF, the test time increases from 5 to 6 seconds)

    The leakage will increase with voltage and this will result in a reduction in the percentage of the voltage after 5 (or the corrected number of) seconds.

    The test ends when the capacitor vents or explodes, the charge voltage no longer continues to rise, or you're charging to no more than 90% of the charge voltage.

    For safety, I'd estimate the voltage rating at somewhere between 50% and 75% of the last test voltage.

    If this is less than the voltage that the first cap failed at, you're probably good to go. If it is greater than that voltage then the capacitors will need reforming before use. You may get away with a slow charge to your rated village, or it may require several cycles at increasing voltages.

    Sounds like a great way to while away an afternoon.
    bushtech likes this.
  3. shrtrnd


    Jan 15, 2010
    Thanks *steve*. I'll stick a few of them on a Secore 'Z' meter and that'll give me the capacitance value. But as you noted, not what the working voltage is supposed to be. I'll have to zap a few of them to estimate that. Once I get a voltage that charges them without damage I can run all of them through the 'Z' meter to check them and see which
    ones will still hold the charge.
    I've got a lot of old Motorola Communications parts. That is a standard numbering system for their parts. Motorola appeared to have proprietized their parts to keep competitors from repairing their gear. I was kind of hoping I'd
    hear from somebody who may know where to cross ANY of the Motorola Comm numbers.
    Who knows, maybe Motorola never even gave their techs that information so that there would be no chance of any of their techs spilling the beans about cross-references, insuring that the techs only used Motorola parts and never disclosed the actual identity of those parts.
    Who knows. If Sony hadn't been so stingy about being proprietary, Beta might have actually been competitive with VHS.
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Sorry, I posted my response without reading too closely who posted it. *Blush*

    Maybe I will edit it back to a couple of lines :-D
  5. shrtrnd


    Jan 15, 2010
    Whew. Couldda been worse. Mightta had my entire post deleted!
    Sure wish I could find somebody with some cross reference on a Motorola Comm parts list.
    Also picked-up a bundle of Motorola Communications 80D83164B01's.
    Fortunately for me, the ORIGINAL manufacturer part number is still stamped on them (Magnecraft 22RX-103A relay)
    I've got a LOT of 'obsolete' Motorola Comm NOS (new-old-stock) parts. I'm guessing most of them are for radios
    that are also obsolete now, ... but I continue the hunt for a cross-reference.
    Good reply to my question in the post though *steve*, somebody running across it in a Google search will also appreciate it.
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