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S5KC20 and V19B Equivalent

Discussion in 'Datasheets, Manuals and Component Identification' started by s57aw, Nov 4, 2014.

  1. s57aw

    s57aw

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    Dec 18, 2013
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
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    Jan 21, 2010
    The V19B might be replaced by a 1N4002 (1N4004 may be more easily available). I'm assuming it's used as a low frequency rectifier or similar.

    The S5KC20 is a pair of 5A 200V fast recovery diodes in a series connection. The only thing I can find is this. (It's surface mount)

    edit: it would be very useful to know where in the circuit it;s used as that may allow us to provide a better recommendation.
     
  3. s57aw

    s57aw

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    Dec 18, 2013
    Thanks Steve... I found some alternative as well available locally. What do you think about this

    MUR120 - alternative to V19V
    http://www.ic-elect.si/pub/files/product_files/165501200100.pdf

    MUR1620CT - alternative to S5KC20
    http://www.ic-elect.si/pub/files/product_files/165516200100.pdf

    Parts are from DC - DC converter from RF amplifier
    http://www.qsl.net/icom/ic2kl/2kl_dcdc.html

    Converter generates +13.8/-13.8v from DC 40v. Q1 and Q2 oscillate about 14kHz and switch the DC 40v to convert it to an AC voltage which is stepped down ba L2 transformer and rectified by D5 and D6 for -13.8v and D7 for +13.8v.

    Robert


     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
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    Jan 21, 2010
    Which ones are D5, D6, and D7? It's a little odd that you have a series connected double diode in any of these positions.

    If these are simply rectifiers for the output, then I would wonder why appropriately rated Schottky diodes aren't used. But I'm not the designer.

    And after looking at the schematic, the SSKC20 is a dual diode with common cathode, not a series connected diode (It's remarkable how helpful the circuit is!). This also makes it far easier to find a replacement.

    I agree that the MUR120 is an acceptable replacement.

    And I believe the MUR1620CT is also a suitable replacement. The only caveat is that I would check that the tab of the original device is connected to the common cathode. If it is not (it may be insulated) then you will need to ensure that the device is electrically isolated from the heatsink.

    Also (and I should have mentioned this earlier) I don't know where you're from so it's hard for me to suggest parts that are easily obtainable locally. This was moot for my original recommendation due to the assumptions I made (which, on seeing the schematic, were clearly wrong). You did a far better job of finding alternatives.
     
  5. s57aw

    s57aw

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    Dec 18, 2013
    This is quite old design (from 80's). Icom is well known radio designer and I do not know either why they took this design, maybe there is a question of oscillation or interference regarding Schottkies. Anyway, I rebuilt everything, replaced all old electrolytic caps, diodes etc... and it works OK. I used MUR120 and MUR1620 diodes. Yes, S5KC20 has common cathodes, I should have mentioned this earlier. I had to isolate heatsink, you were right again. Thanks

    Robert
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    Yeah, there is little point second guessing the designers. Maybe the reason was the extra expense of the Schottky diodes, or maybe there was another reason similar to that you suggest.

    I notice that page recommends replacing some electrolytics and adding some 0.1uF caps. I'd recommend that if you've not done this that you do so. The caps will be getting old and this can contribute to noise in the receiver. Some nice new low ESR 105C rated caps will improve the noise performance, and the extra 0.1uF caps won't hurt either.
     
  7. s57aw

    s57aw

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    0
    Dec 18, 2013
    Great... Yes, I have replaced all electrolytics... they are 20+ years old and 2 of them were damaged that I couldn't read or measured the value. That was also the reason that I need to repair / rebuild everything. All electrolytics are replaced and I have also added extra 0.1uF caps as suggested. I replaced also all four old resistors and all diodes and should be OK for next 20 years :)
     
  8. i2jjr

    i2jjr

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    Feb 2, 2019
    s57aw: Please Robert, did you also substitute the 2SC2501 transistors? (I did as suggested with TIP33c, bleah, larger) I had a similar failure in my IC2-KL, the inverter not working anymore; ALL components have been substituted with equivalent as suggested also by other hams; note that ALL devices substituted proved to be OK or in good order, no faults; anyway the inverter does not work just as it did before. The transformer seems also to be OK. I then substituted the inverter with a self designed tracking power supply and all works fine; but the enigma - or mistery - of the non inverting inverter remain unsolved. 73, i2jjr / hb9tza August
     
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