Success at last

Discussion in 'Off-Topic Members Lounge' started by gunnadoo, Nov 11, 2017.

  1. gunnadoo

    gunnadoo

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    hi, i hope this is off topic enough ,as it is not a question. anyway it all started many moons ago, when old mate give me a beginners electronics book. i knew the basic ohms law, as i have been off grid power for 27 years now. so i tried to make a transistor work. so after lots of tries/ failures, i swore and cursed and gave the bloody book back. fast forward to 5 days ago, i decided a transistor would solve my problem .
    so get on www and try and learn again, [i am proficient with metal and wood though], i still had a couple of bd139,s from way back ,so give it another go. i sort of got one to work, but the relays stayed latched on , after i turned base off!...? . ok try the other one, FAIL !. during these tests i destroyed the MA function on 2 dmms.
    so, off to jaycar , [electric/onics retailer] for $10 dmm and 4 [bc338] and 4 [pn2222a] transistors]. at home i double check data sheet and EPs guide/equations [pn2222]. all good, connect c/e to load [40MA relay coil] and on it goes !..what the *%&#. the base was not connected yet . so i triple check data sheet , equations and wire connections again. try again , same thing , this is really starting to do my head in , [doubting my sanity] , flash backs to my first attempts etc. i was at a loss and ready to kill anything with a transistor in it.
    arghh, then the "penny dropped" , to check numbers on transistor, so,i had to find a microscope [nearly] to read the numbers [p2n2222a], back to google ,123=CBE whereas [pn2222a is 123= EBC] . they are one and the same. i specifically asked for [pn2222].... what is it,? about engineers ,that they have to complicate everything..the moral about this story is, rule #1 never trust a salesman. rule #2 [see rule #1] sorry about the rant , and i will ask my questions in the appropriate forum...

    regards..
    dennis..
     
    Last edited by a moderator: Nov 12, 2017 at 2:59 AM
    gunnadoo, Nov 11, 2017
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  2. gunnadoo

    HellasTechn

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    This story reminds me of myself... Never i had started a project and had sucess right from the beginning.

    Anyway the DMM's have a small fuse inside. You should check it before you throw them away.

    Also you should buy one of theese... I can not live without it anymore !
    it measures transistors, fet's, diodes, capacitors, resistors and many more.

    https://www.ebay.com/itm/LCR-T4-LCR...hash=item5d6b4d939a:m:mVttfkmvKz6Sp-ldjPpNqOw
     
    HellasTechn, Nov 11, 2017
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  3. gunnadoo

    gunnadoo

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    thanks for the link, just bought one. also does anyone know if there is a gadget/shunt type of thing that will measure, say , 1 mA to 10 Amps

    thanks..
     
    Last edited by a moderator: Nov 12, 2017 at 3:00 AM
    gunnadoo, Nov 11, 2017
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  4. gunnadoo

    Bluejets

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    Most standard, elcheapo even, multimeters will cover from 1mA to 10A dc.

    You just need to learn to double check connections before switching on the power and set the meter to the appropriate scale beforehand.

    If in doubt, select high range first.

    As far as transistor testers, one can get by with just the add-on again in the elcheapo meter.

    Most of my bench work is done with a $50 digital multimeter and a capacitance meter.
    Also keep an old analog meter handy for when the digital will not cut it.

    In the field with electrical it is a different story requiring the up market gear.(high catagory meters)
     
    Last edited: Nov 11, 2017
    Bluejets, Nov 11, 2017
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  5. gunnadoo

    gunnadoo

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    thanks, but my impatience/dementia fails me lots of times and changing the plugs and switching from mA to A often, annoys me. [ maybe i need impatience counseling ].
    i was thinking a meter with 2 leads that would measure both.

    thanks..
    dennis
     
    Last edited by a moderator: Nov 12, 2017 at 3:01 AM
    gunnadoo, Nov 12, 2017 at 12:37 AM
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  6. gunnadoo

    Bluejets

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    It's not that difficult.:confused:

    If you are having trouble now, wait until you get past basic on off.
     
    Bluejets, Nov 12, 2017 at 2:25 AM
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  7. gunnadoo

    shrtrnd

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    Impatience with those amperage readings will blow the multimeter internal fuse.
    If you think you get frustrated now, it'll be worse after blowing your meter fuses a few times.
    Try to remember to stop and think before making those current measurements and you'll stay happy.
     
    shrtrnd, Nov 13, 2017 at 1:48 PM
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  8. gunnadoo

    HellasTechn

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    Well, Its normal to make mistakes and blow a few instruments and destroy a few boards... Who has not done that as a beginner ?
     
    HellasTechn, Nov 16, 2017 at 7:12 AM
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  9. gunnadoo

    bushtech

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    gunnadoo, I feel for you, been in that boat too many times myself. My current head do inner is isolating a BD139 from a heatsink.
     
    bushtech, Nov 16, 2017 at 8:00 AM
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  10. gunnadoo

    HellasTechn

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    Aren't the BD139 plastic ?
     
    HellasTechn, Nov 16, 2017 at 8:33 AM
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  11. gunnadoo

    bushtech

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    Yes, but the underside has got a metal pad for heatsinking
     
    bushtech, Nov 16, 2017 at 8:38 AM
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  12. gunnadoo

    HellasTechn

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    HellasTechn, Nov 16, 2017 at 2:28 PM
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    bushtech likes this.
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