Wall Clock Chime Melody - Page 1
Forum section: electronics / repair

author: Grandmaster
author_rank: Newbie
timestamp: October 12, 2019, 08:59:23 pm
content: Hi All,Trying to repair a wall clock with a melody/chime circuit.There is a long story with this which I won't bore you with but I would like to get it repaired.There are two wires which seem to trigger on the hour.Two wires for the speakerTwo wires for a switchTwo wires from the battery packA transistor S8050A 4.7uF capacitorA Resistor (not sure of the value)An IC? that is under a black blob of epoxyI have hunted all across the internet and can find some melody boards but none like this.It has no other markings except for WLI have taken some pictures and mapped out the board if that helpsI would appreciate an idiots guide on how to wire this back together. (imagine you are telling a child lol)At the moment I have soldered the battery pack to the cap + - and the speaker to the Left leg (emitter?) and the other speaker to the capacitor negative lead. I cannot seem to get this to trigger.Thank you in advanceGM

author: floobydust
author_rank: Super Contributor
timestamp: October 14, 2019, 04:31:06 am
content: Welcome to the forumsI'll take a kick at it, to find the circuit does not make sense, there's an error somewhere.S8050 NPN pinout EBC, so the collector (right leg?) goes to a pad that should connect to the speaker(-). The emitter should go to ground, battery (-). Speaker (+) to battery (+).This would mean the capacitor is factory installed backwards, it is known to happen in the sweatshops.If the transistor pinout is flipped CBE, then still an error as the cap(+) goes to the collector which is the wrong polarity for an NPN transistor.I don't see six wires (solder points) going to the board.The fat trace by WL logo might just continue under the blob to the pc board's left edge. I would check with ohmmeter.The trace along the bottom edge might be open-circuit, it looks a bit torn. I would check with ohmmeter.I'd hate to tell you to connect power backwards- you can use a multimeter on diode-test and see if you get a reading across the cap with either polarity. Backwards should read one diode-drop I believe.Sound chip data:http://projects.whatimean.ch/2017/04/21/chinese-sound-chip-board-pinout/https://www.aliexpress.com/item/32714286619.html?shortkey=3ieAJFZf&addresstype=600

author: Grandmaster
author_rank: Newbie
timestamp: October 14, 2019, 09:19:33 am
content: Good morning,Thank you for your reply, I am at work at the moment so I will read and digest your response tonight.Thank you for replying, very much appreciated!!Gm

author: Grandmaster
author_rank: Newbie
timestamp: October 14, 2019, 06:44:05 pm
content: floobydustMate,You absolute LEGEND!!I wired it up just as you laid out S8050 NPN pinout EBC, so the collector (right leg?) goes to a pad that should connect to the speaker(-). The emitter should go to ground, battery (-). Speaker (+) to battery (+).and it started chiming away.I need to work on the trigger as it only trigger when I manually place a wire but it's further than it was.YOU SIR ARE A LEGEND!!!I will follow this post with some pictures for future people but that will have to wait until weekend as I have some work to do.Thank you again.