Connect with us

First Post - Help with Identifying Circuit Components

Discussion in 'General Electronics Discussion' started by Hobby Junkie, Mar 20, 2016.

Scroll to continue with content
  1. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Hello. This if my first post on this forum and thanks for allowing me the opportunity to interface with you members. I have been a long time junkie when it comes to various hobbies from carpentry (framing & finish) to machining (mini mill & mini lathe) to auto repair, general contracting (slab to roof) to all other sorts of other things. I am in my early sixties, am retired from the US Army after 20 years, and unfortunately am 100% rated disable by the VA for several service connected disabilities. So my life now is solely around my wife and my hobbies.

    I am having an issue with a laser circuit I am working on. I lost the laser-photo diode and have to replace it with another laser-photo diode. I also believe that this is a current driven system. But the main issue is that there are three components that I can not find any information on.

    Anyways, I have identified most of the components on the laser driver board but am having problems identifying 3 components on the SMD board. The specific components are the diode (either a Zener or Barrier - based solely on an assumption [current limiter maybe???]) that I can not identify at all. It is marked is a while line indicating the polarity and the name "ASb". The other two components are what I believe to be Bi-Polar Junction Transistors ???, one is a PNP the other is a NPN. These are marked "6CW" with an "82" perpendicular to the "W" and the other is marked "5AW" with "60" perpendicular to the "W". BTW, the DC de-coupler??? cap is 1uF.

    Anyways, I was hoping that someone here could assist me with identifying replacements for these components.

    It is a relatively simple circuit where the input to the photo diode monitor side (laser diode output) of the laser-photo diode limits the driver circuit that drives the laser-photo diode on the laser side. It is a 3VDC system driven by a CR123 battery.

    Here is a picture of the SMD board with the components I can not identify circled.

    Any assistance would be appreciated.

    Picture of the board with the components that I need to identify:

    [​IMG]


    Schematic (I think...my attempt even though I know that it is not as "accurate" as it could be for component identification in a schematic drawing - sorry....)

    [​IMG]

    I want to be sure that the components are replaced before I hook up another laser-photo diode so I do not "burn" the new diode as well.

    Any help with this is really appreciated. And again, thanks for allowing me to post here.
     
  2. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Was not sure whether to put this in this forum or the next one down. Sorry if it is the wrong forum and please move it if it is in the wrong forum. Thanks.
     
  3. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    it's ok here :)

    the diode ... ( no it's not a zener, incorrectly connected for that) it's a general purpose switching diode
    http://www.s-manuals.com/smd/a5

    transistor 6CW
    http://smdcode.com/en/smd/code/6cw-bc817-40-silicon-npn-transistor-88300/

    transistor 5AW
    http://www.s-manuals.com/pdf/datasheet/b/c/bc327,_bc807,_bc807w_series_nxp.pdf


    google is a good thing to use


    Dave
     
    Hobby Junkie likes this.
  4. 73's de Edd

    73's de Edd

    3,122
    1,315
    Aug 21, 2015
    Sir Hobby Junkie . . . . .

    The 5AW transistor should be having the PD sampling going into its base , reverse your 5AW B-E markings.

    I am going to have to split this up into two sessions but the info
    on two of the three are below, plus the last ? one :

    5AW info:
    http://www.s-manuals.com/smd/5a

    6CW info:
    http://www.s-manuals.com/smd/6c

    ASb is still up in the air . . . . .but check . . . .
    http://www.s-manuals.com/smd/as

    Still musing that 1 ufd on the "cold" end of the DPDT switch . . .if you have "read" the board right .


    73's de Edd
     
    Last edited by a moderator: Mar 20, 2016
    Hobby Junkie likes this.
  5. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Thanks so much for you help. I did use google and all other sorts of search engines including MSC and Mouser and the Russian site mentioned in the Sticky at the top. It appears that my Google Foo is not as strong as it should be but as I indicated, this is a hobby that i work in usually only a couple of times a year so with the myriad of components and my total lack of knowledge about this stuff, sometimes I feel totally lost.

    Thanks and let me get to some reading.
     
  6. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016

    Thanks Dave. I did some research before hand and did find the BC817 and saw that the marking code 6CW (W indicating China manufacture) as a NPN transistor. I also found the 5AW as a BC807 PNP again with the W indicating manufactured in China but was not 100% because it was listed as a BC807-16 or BC807-16W, and the BC817 likewise was listed as BC817-40 or BC817-40W

    I wondered if it was a "5" instead of a "S" but alas, my electronic skills are limited to a high school vocational program (little learned about semi conductors in the late 1960's. After that, it was just one semester of general circuit analysis in college.

    I will read the manual recommended for the general purpose diode.

    Thank you so much for the pointers.
     
    Last edited: Mar 20, 2016
    davenn likes this.
  7. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Thank you as well. I was not sure about the PD B-E markings and am glad that you saw that and pointed it out to me.

    As mentioned in the previous post, I was wondering whether it was an "5" or an "S" as well??

    There is only 1 cap of 1uF on the board as the decoupler??? It is the only cap on the board and I removed it to make sure that the schematic print was correct on the leads. That one had absolutely no markings on it what so ever so I ended up using my Cap meter to verify the rating. It came out as 1.01uF on the meters 20uF setting. I searched for color coding as well as sizes to try to figure it out as well.

    I am learning that the SMD components are way to small for the proper markings and it seems I have a whole new study program to initiate.

    Thank you as well for your assistance.
     
    Last edited by a moderator: Mar 21, 2016
  8. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    yup, but it's weird that it would be connected directly across the battery when the switch is in the off position
    That would be unnecessary


    Dave
     
    Hobby Junkie likes this.
  9. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Dave

    I do think that it is a diode. I took it off the board and here are some better pictures of it. It has only 2 contact points and I am still pretty sure that it is marked "ASb" not "A5*"

    Based on the circuit design, I think it is used as a protection component in a current limiter fashion. But, I am no where educated on this but after review of the A5 data sheets, it does not look to me to be the same.

    [​IMG]

    [​IMG]

    [​IMG]

    Thanks again for your assistance.
     
  10. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    It's not. It is a three position switch. The middle position is off. I will mark the schematic accordingly with the left side low power, middle is off, and right side is high power.

    The left position (low power) activates the positive side of the circuit (upper pin) while the bottom pin (neg) goes nowhere. The right position (high power) activates the positive side (upper pin) while the bottom pin bypasses the 33kohm resistor on the neg side. And as mentioned, the center position is the null position. So the upper three pins are all positive and the lower three pins of which only two are used, bypasses the 33kohm resistor, on the neg side.

    Thanks for checking it out.
     
  11. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    regardless, it still puts that cap directly across the battery in that position which is still pointless


    that doesn't gel with what you have drawn. If it was centre off, then none of the contacts would be connected

    the only other thing it would be then is a tantalum capacitor and the white bad on one end indicating the positive terminal
     
    Hobby Junkie likes this.
  12. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Don't know. The schematic is accurate about the cap. I removed it from the board just to make sure that the circuit was correct. I will post a picture of the board in the AM with the component removed, and I will update the switch as to how it makes contact.




    That is correct. When the switch is in the center position, there is no contact on the upper or lower side of the switch. It is like a two switches in tandem (although a single unit). If you mark the upper pins as A, B, C and the lower pins as D, E, and F, when the switch is thrown to the left, there is contact between A and B, and contact between D and E ( D & E goes nowhere). Throw the switch in the right position, and there is contact between B and C, and E and F (this bypasses the 33kohm resistor). There is never any contact with A, B, or C, with D, E, or F in any position. The B E position of the switch is the "null" with these two pins making no contact with anything.



    Again, this is the first I heard of a tantalum capacitor. I will do additional research with it. However, if it is a diode, mayby a Schottky Barrier as seen here? http://pdf1.alldatasheet.com/datasheet-pdf/view/121479/ANACHIP/ASB00340.html
     
    Last edited by a moderator: Mar 22, 2016
  13. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Does it make more sense drawn this way.....

    [​IMG]
     
  14. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    Yes now knowing that that is a 2 way centre off makes a difference, it means the cap is now across the +V to ground
    in the hi or lo position :)


    I'm really not convinced as to if it is a diode or a tantalum cap cant find anything definitive for AS as a diode or a cap

    whichever it is, you have it drawn around the wrong way ;)


    Dave
     
    Hobby Junkie likes this.
  15. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Of course you are right. I'll get that corrected.


    I thought the Anode was POS and the Cathode was NEG.
     
    Last edited: Mar 21, 2016
    davenn likes this.
  16. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    Just wish we could figure out which it is

    I see more logic as a cap than as a diode

    don't think you mentioned measuring it with a multimeter in Ohms range
    if a diode it will be hi resistance one way, 100's of k Ohms and low resistance the other way
    maybe a few 100 Ohms or so

    if a cap, you will see it slowly charge up and swapping the test lead polarity it will do the same again
     
    Hobby Junkie likes this.
  17. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    550 MEGA Ohms, but fluctuates as expected. Does not act like a Cap when I use my cap tester on it.
     
  18. Hobby Junkie

    Hobby Junkie

    18
    4
    Mar 20, 2016
    Did not see you were in Australia. After 1AM here so I have to call it a night. It will be another sunny day in Florida tomorrow but at times I wish I was still there. I only spent a short time in Alice Springs but would like to come back and visit again.

    This unit was manufactured in Australia BTW.
     
  19. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    in both directions ?

    hmmmm ok

    The Alice is still on our to go list ... a couple of summers ago My wife and I went to Uluru ( Ayers Rock) ( pretty much the centre of the country a long way south of Alice Springs

    I go to the USA periodically, mainly in the mid-west for storm chasing. Haven't been to Florida yet. Always wanted to go to the "Cape" to see a shuttle launch
    but didn't happen before the program ended :(


    Dave
     
    Hobby Junkie likes this.
  20. 73's de Edd

    73's de Edd

    3,122
    1,315
    Aug 21, 2015
    .


    Sir Hobby Junkie . . . . . . .

    Session Deux . . . . .


    I was able to make out enough on the first viewing of your reverse engineered drawing and mark in changes and add some info right on your schematic sheet .

    First of all . . .might this just be an internal dedicated ancillary circuit to one of those " wun hunnerts ninety nines dollahs " tactical flashlights, since its being built on a round PCB.
    Usually all of this ciruitry is built on a mini sized monolithic chip as the Laser driver circuitry.

    Questions that I need further info . . .I am going to Bullet . . . . to be easily seen.

    I am "reading" the board and seeing the battery wiring coming in to A and B copper lands that have NOTHING else connected to them, except for the foil path from A over to E.
    Then there is the additional foil path from B to F.
    These are the central pins on the DPDT switch, with the left C and D lands being unused / vacant.
    On power on the E to G connection is being apparent for the + power insertion.
    You can see I placed the 1 ufd over where it belongs.
    As for the F to H connection that will require a bit of pulling the battery and ohmming out by you.
    Look at the PD photo diodes output coming down to this circuitry . . . I am wanting to be seeing those two resistors being used in a voltage divider function with the final
    output ending up at the base of 5AW.
    As it stands switch F-> H is merely doing an illogical switching of a short across the 33K resistor. . . . . .ha . . . ha . . . like it needs to be in circuit while the unit is OFF but
    needs to be shorted out when the unit is turned ON.
    What I am now seeing is enough to give you:

    CONCEPT OF DESIGN :

    Flip the power switch and + power is applied to the Laser diode and it is wanting to find a ground path to activate.
    Simultaneously with that power on, a 1.2 K resistor is giving base drive to 6CW so that ground path is then found via Collector -Emitter conduction of 6CW.
    That base drive supplied is a bit more than needed, as the detected Laser output level is being monitored by the
    photocell PD and will be supplying power correction via a feed back loop.
    Note that the base of the 6CW transistor takes a path to the left and initially encounters a RC time constant which will give in the order an
    ~ 80 MS "hang" time on corrections. That path ends at the collector of 5AW . . . . . as the output from the PD increases it progressively
    shifts base drive of 5AW and causes it to conduct more heavily and that progressively pulls down the voltage on the initial base drive of 6CW
    to a stable correcting value..

    • Pull the battery and ohm out and inspect to find out the real wiring path on the basic area within the RED dotted lines.

    After that use a DVM in its diode test mode to ascertain and pass us back all of the Vf of all of the junctions of the two transistors, as well as the
    slight possibility getting readings from of the Laser diode and PD.
    The real work horses are being the 6CW and the Laser diode.

    • Fulfilling that info . . . . .round up anywhere from 1/2 thru 2 watt . . . . . . 100 and 220 ohm resistors and I will tell you howtodoittoit next.
    Thasssit . . . . .

    Addenda:
    I see that my assignment of the switch Alfa designations differ from yours, because I used up my AB on the battery lands, and thereby created the resultant error on the CDE and FGH designations.


    Redraw of your Techno Referencing:

    [​IMG]




    73's de Edd


    .
     
    Last edited: Mar 21, 2016
    Hobby Junkie likes this.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-