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Dewalt DC012 radio - No sound

Discussion in 'Troubleshooting and Repair' started by Gilles H, Oct 18, 2020 at 3:13 PM.

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  1. Gilles H

    Gilles H

    6
    0
    Sunday
    Hi, I have a Dewalt DC012 radio, no sound anymore. I measure the output voltage of the power pcb assy (which feeds the radio pcb), it is supposed to be 13V, but is 16V (circled in orange on picture).

    My question is: could this extra 3V prevent the radio board to function properly?

    I did a visual check, iI cannot see anything damaged or burnt on each pcbs, front and back, except for the area behind the resistor (circle in red) where the pcb changed color. The resistor's color bars indicates it is a 15 ohms resistor which measures good. The two blue relays on the left get pretty hot too.

    Thank's

    Gilles
     

    Attached Files:

  2. Bluejets

    Bluejets

    4,210
    893
    Oct 5, 2014
    Cannot make out anything as photo detail is low.

    Are you running on battery or mains supply?

    Has the aux port been used?
     
    Last edited: Oct 18, 2020 at 10:41 PM
  3. 73's de Edd

    73's de Edd

    2,913
    1,233
    Aug 21, 2015
    Sir Gilles H . . . . .

    Referring to the resolution limitations being provided by your . . . .DC012.jpg photo.
    Your fretting of the relays and hot resistor can be allayed as they are being associated with the tool battery charger portion of the unit.
    The sole radio aspects portions are being its power transformer at the right top corner of the speaker frame, then its power board as the one with the fuse and 4 rectifier diodes and storage capacitor(s) being right in line with the top of the speakers central whizzer cone. this is outputted as your mentioned DC voltage supply which routes into your ORANGE circle at the radio PCB.

    All is being well up to there and then you see where my drawing continues with your same ORANGE circle reference.
    Now they may use that full voltage that you are encountering in the supply down at the AUDIO output IC.
    BUT . . . . now investigate to see the corner heat sink and its associated power device. ( YELLOW rectangle mark up in two places. )
    Looks like it has a Q4 ? as its assigned designator . . . . . thereby making it a power transistor vice a normally suspected 3 terminal regulator.
    See if it is not working in conjunction with the small transistor at its side to make a voltage regulator stage to drop your inputted voltage down to a yet lower level supply voltage.
    If so, you will find full voltage on its collector and the reduced / regulated voltage being outputted at its emitter.

    Then as per my YELLOW STAR, you probably will find that IC1 device as being a 3 terminal regulator dropping down to a 5V logic supply level.

    Supply those parts numberings and we will then sort them out to see whas happening ?


    Thaaaaaaaaaaaaassssssssit . . . . .fer now . . .

    A MO' BETTAH RADIO CIRCUIT BOARD REFERENCING . . . . .

    [​IMG]


    https://i.postimg.cc/Q8xYGWGT/DC012-Radio-Board.png


    73's de Edd . . . . .

    I came home and my dog peed a little because he was s o o o o o happy to see me.
    Now, in my thinking about it . . . . . NONE of my friends pee when they see me.
    Know whuts ? . . . . . I'm now fully beginning to think that I am being surrounded by fake friends.



    .
     
  4. Gilles H

    Gilles H

    6
    0
    Sunday
    Thank you for the replies.

    To Bluejets: I plugged in the AUX, no sound neither.

    To 73's de Edd: I have limited electronic knowledge, I can only repair the obvious. I cannot identify he big IC with the butterfly heatsink as the heatsink is soldered and would prefer to unsolder as a last resort, If you absolutely need it for the pinout, please let me know.

    The small IC (yellow star) has something that looks like '78M08' printed on it. Datasheet: https://www.google.com/url?sa=t&rct...heet/l78.pdf&usg=AOvVaw0L7cc0_wWEocAIvbEOmE50

    B1370 datasheet: https://www.web-bcs.com/transistor/tc/b0/B1370.php?lan=en&cl=1

    I took closer pictures. Due to the limited information available, please let me know if you find worthed to provide a step by step testing of the suspicious components to find the culprit, I would follow the instructions.

    Thank you,

    Gilles

    Yellow star IC:
    2020-10-19 09.50.09.jpg

    Yellow star IC close-up:
    78M08.jpg

    Small yellow rectangle (B1370):
    2020-10-19 09.49.14.jpg

    Large yellow rectangle solder side:
    2020-10-19 09.52.43.jpg
     
  5. Gilles H

    Gilles H

    6
    0
    Sunday
    To Bluejets: sorry, running on main, got no batteries. Thank you, Gilles.
     
  6. shrtrnd

    shrtrnd

    3,763
    485
    Jan 15, 2010
    You'll probably get more help from Bluejets and 73s de Edd, I'm just jumping in here to mention the 78M08 is a +8V voltage regulator, and you can check for the voltage on that component while waiting for additional help.
     
  7. Gilles H

    Gilles H

    6
    0
    Sunday
    Thank you for your reply. I measure 11.91V at input and 7.99V at output.

    Thank you,

    Gilles
     
  8. Gilles H

    Gilles H

    6
    0
    Sunday
    Hi, I noticed that my DC012 PCB is another version than 73's de Edd. Here are more picture if this can help. Thank you, Gilles.
     

    Attached Files:

  9. Gilles H

    Gilles H

    6
    0
    Sunday
    Ok, thank's to everyone. Project closed, radio sent to recycling center. Gilles
     
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