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June 17, 2013 at 12:46 am #22482
I just finished soldering on all the components. I started with the testing procedures.
24 AC transformer reads 27.9 – 28.0 volts when not connected to anything.
When I powered on, Vin to ground read 1.0v DC, then went to 0.8. IC1 started to get hot so I switched it off. I noticed that L1 Power Inductor was hot too.
I don’t see any shorts. I did notice that IC1 part name in the instructions does not match the part that was shipped in the kit. The other ones matched, and the numbers were close so I assumed that I had the right one and maybe there is a part number difference. The IC in the kit has part description stamped on it: ST CHN 063AC 41E241. In the instructions it is referred to as MC34063. Not sure if that is a problem or just an updated part number.
Let me know what I should test next, or if I should look for a different IC1.
Here is a picture:
Here is a picture of the soldered connections:June 17, 2013 at 1:59 am #24504
The part name difference should not be a problem: we buy parts in different batches. Usually even if you order from the same supplier a few days apart, the part number can be slightly different. ‘ST CHN 063AC 41E241’ is an MC34063 chip, so no worry about that.
You can use this thread as a reference to troubleshooting:
My suggested list in order:
1. test the resistance between VIN and GND. If it’s less than at least several kilo-ohms, some components must have been damaged and shorted. Start with zener diode D3, desolder it or simply clip it off, measure VIN-GND resistance again; if still too low, desolder or clip the MCP1703-33 linear regulator. Basically follow the components that have to do with the VIN line, and check them one after another, and replace if necessary.
2. If the VIN-GND resistance is above several kilo-ohms, the next thing you should try is to power the controller through USB. Plug in a USB cable, and measure VIN-GND voltage, which should be somewhere around 4.7V to 5V. Then measure VCC-GND voltage, which should be around 3.2 to 3.3V. At this point, you can plug in the other ICs and the controller should function normally (except since there is no 24VAC it can’t activate solenoids).
3. If your MC34063 is damaged, you should get it replaced. The final step is to go back to what you did before: test the power supply with 24VAC transformer. Just to be safe, you should take out all ICs except IC1. If it passes the voltage tests, you can then plug all ICs back.
To get replacement components, you can either follow the part list to buy them from Digikey, or you can send me an email and I will send you requested components at a nominal cost.June 18, 2013 at 12:45 am #24505
Thanks for the tips.
I started with step 1 and found that the resistance between VIN and GND was low, ~4 ohms. I removed IC1, then started taking components off. When I took the zener diode D3 off, the resistance went up to around 80 ohms. So I continued taking things off. I took IC2 off, C2 then D2. At each step I started to notice that it depended on the mutlimeter’s polarity as to whether I’d get the 80 ohm reading or not. After taking D2 off I got a high resistance. Then it dawned on me that the polarity probably does matter on the multimeter since we’re checking a diode. Anyways, 80 ohms also seems too high to me for D2 but I don’t really know much about Schotky Diodes… or maybe my mutlimeter isn’t effective at measuring it.
So I checked the zener off the circuit board and it measures ~2 ohms in both polarities so I think that is definitely shot.
I believe the root cause to be a small wire clipping from one of the other components that was sitting on the top side of the board which I noticed after the first power on. It was near the 24 vac components so could have shorted something.
I’ll send a PM requesting some replacement parts.
GlenJune 28, 2013 at 3:24 pm #24506
I received the replacement components and soldered them in place. Everything seems to be working well now.
I’m sure the zener diode was destroyed because the resistance between the new and old one was very different. I also replace IC1 and D2 at the same time – not sure if there were issues with these components or not, but they were already out, and I had new ones to put in. I checked resistance between VIN and GND and measured >10 kohms, and about 80 ohms depending on which way I put the leads on. After powering up, VIN read 5.0 v +/- .1 and VCC was 3.3 v +/- .1.
The display is functioning as expected.
I’m struggling a bit with my ‘mini-router’ now but I think I make a new thread for that.
Thanks for your help!
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