Fried!

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3 months 1 week ago #12050 by Dave
Fried! was created by Dave
So, I finished the build of my IN-8-2 all-in-one clock and all seemed to be going well. Almost. I had it on and got the Wi-fi set up. I could get into the setting but couldn't change them. It wouldn't update from the time server.

Ok, not too bad so far. It gets worse. Today I try it again. It would not connect to the wi-fi at all. I leave it on for about an hour to see if it would eventually connect. When I checked on it everything was off and the 7805 in IC1 was very hot.

Uh,oh. It gets worse. After unplugging it and letting it (and myself) cool off, I plug it back in so I can probe around with my meter (like I have any idea what I'm looking for). I accidentally brushed one of the leads across the pins on SV1. Either VIN and ground or VIN and VCC. I'm not sure. Lights out except very dim backlight leds. The power indicator led stayed on.

Obviously I fried something but I'm hoping it is salvageable. Any ideas where to start?

Dave

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3 months 1 week ago #12052 by Ian
Replied by Ian on topic Fried!
Hi Dave, this stuff happens. Let's see what took a hit.

From the top:
1) Unsocket everything. All socketable components out (controller, optos and K155).
2) Test the 5V test point. If you still read 5V, we know that the 7805 is still working.
3) If you have 5V, let it run for a while and see if the 7805 gets hot.
4) Put the controller back in, but leave everything else off board.
5) Check the 5V again. Still got 5V? Does anything get hot?
6) If you get past this point (I don't think so) we can start putting the other components back on.

My best guess is that the controller has taken a hit. If you happened to brush VIN to VCC, we'll have given the controller and the K155 over voltage. The K155 might survive it, but the controller won't.

If on the other hand you shorted GND to VCC, the 7805 will have been shorted. However 7805s have internal short protection, and it should have survived.

Let me know!

Regards

Ian

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3 months 1 week ago #12053 by Ian
Replied by Ian on topic Fried!
Oh, and don't worrry about it - I'll provide you with replacement parts free of charge. It comes with the territory that stuff happens.

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3 months 1 week ago #12054 by Dave
Replied by Dave on topic Fried!
Thanks Ian,

I got to step 5 above and its right at 5v and nothing is hot.

One interesting thing is when I touch the controler the led backlights get brighter.

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3 months 1 week ago #12055 by Ian
Replied by Ian on topic Fried!
They just get statically bright, no flashing or pulsing or anything?

Did it get hot before when the WiFi module was in, or before that?

If you connect and hold down the button while restarting, does it flash anything? (This is a "factory reset" - I don't really expect it to work).

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3 months 1 week ago #12056 by Ian
Replied by Ian on topic Fried!
Just to let you know what I am thinking: The 7805 should not get that hot under normal circumstances, but it might if you use a power supply that is unregulated or just unstable. It shouldn't usually get too hot to touch. 9V DC at 1A is the best supply for this clock.

It will dissipate more heat if you have very bright LED settings or something else is drawing current. It could have been a faulty ESP that caused it to get hot.

One step at a time.

I think the controller is probably up the spout, and we have to try and identify the other parts if we can that are candidates for replacement.

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