Dewalt DC012 radio - No sound

[Gilles H]

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

 

[Bluejets]

Cannot make out anything as photo detail is low.

Are you running on battery or mains supply?

Has the aux port been used?

 

[73's de Edd]

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 . . . . .

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.


.

 

[Gilles H]

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:


Yellow star IC close-up:


Small yellow rectangle (B1370):


Large yellow rectangle solder side:

 

[Gilles H]

To Bluejets: sorry, running on main, got no batteries. Thank you, Gilles.

 

[shrtrnd]

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.

 

[Gilles H]

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.

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

Thank you,

Gilles

 

[Gilles H]

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.

 

[Gilles H]

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

 

[PH5]

I had a DC012 radio recently that had the same problem. Charger worked, but the radio was completely dead. I measured 18V going into the radio circuit board, but it most of the voltages on the board were very low or zero. For anybody else that is having that problem, I found out that C228 (a big electrolytic capacitor) near the 78M08 voltage regulator had shorted out. When it shorted, it also blew out transistor Q504 near the audio IC, which is involved in voltage regulation. You should have around 12V at the collector and emitter of Q504 if it is working. Neither one of those were obviously damaged to the naked eye, though when I looked really closely at Q504 I could see a slight bulge in it. I don't know for sure what transistor it was originally, but I used a Y2 SS8550 PNP transistor as a replacement and replaced the cap too. It fired up and worked again after I did. Hope that helps anyone else trying to fix theirs.

PH