Low Voltage Circuit Problem - Modular Nixie Clock

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1 year 3 months ago #9764 by Lexxar
Hi all,

im just starting to build the modular nixie clock, but i am not able to get 5V at the output. I checked the polarity and the soldering multiple times and even changed the IC (the IC isnt getting warm at all). The voltage drop at D1 is fine. I am using a 9V 1A power supply. U guys have any tips?

Best Regards
Jan

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1 year 3 months ago #9766 by Ty_Eeberfest
Not much to go wrong in that LV circuit. My first suspects would be IC1 and D1 but you already checked them. When you tested D1 did you read the drop across it with power on or did you use the diode check range on your meter with power off? This may be a dumb question but I'm just wondering if you're getting power on the board at all, e.g. is the power input barrel connector okay? Are you seeing about 8.4v (supply - 1 diode drop) at Pin 1 of IC1? Ground at Pins 3 & 5?

Other than that, if inductor L2 was defective (open circuit) there would be voltage at IC1 Pin 2 but none at Pin 4. Probably easiest to check L2 with an ohm meter (with power off). It should read close to 0 ohms if good.

I'm not sure what would happen if D3 was bad. It would be a good idea to test it with your meter.

Look into it later when the dust is clearing off the crater.

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1 year 3 months ago - 1 year 3 months ago #9771 by Ian
As long as nothing is getting warmed up, the best way is to check the voltages with the circuit powered up. There are no worrisome voltages here.

Just to put a picture to what Ty just said: check at points 1 and 2, compared to ground. You should get VIN, say 9V at point 1, and (VIN - 0.6V), say 8.4V at point 2. These voltages must be positive. If you read negative voltages, you have a centre negative power supply. D1 is there to protect just for this case.

The best guess at the moment is that you've got the wrong polarity voltage, or no voltage at all.

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Last edit: 1 year 3 months ago by Ian.

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1 year 3 months ago #9772 by Lexxar
Thanks for your tips. The Input voltage at point 1 to GND is 9.1V positive. D1 is about 0V now unfortunately. I am pretty sure it was 8.4V yesterday. The diode seems to be fine though reading 0.495 through diode check on the multimeter. L2 is 0Ohm so it should be fine too. IC1 has GND Connection at pin3 and 5. But no Voltage at all at Pin 1 or any other Pin. So there must be a short to GND somewhere? Maybe i burned the board while trying to desolder the IC?

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1 year 3 months ago #9773 by Ty_Eeberfest
No, I don't think anything is shorting to ground. If it were, I'd expect something obvious to happen: perhaps D1 would get very hot, or the external power supply would either get hot or go into overcurrent shutdown. It kind of depends on the specifics of the power supply.

I know you said you checked polarity on everything but this sure sounds like a case of D1 being installed backwards. Are you absolutely sure D1 is in the right way around? The end with the band (stripe) should go to the square pad, which is the pad nearest to L2.

Look into it later when the dust is clearing off the crater.
The following user(s) said Thank You: Ian

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1 year 3 months ago #9776 by Lexxar
It rly was the orientation of D1. Maybe i was mislead by the text in the manual so i didnt thought about it further. A big thanks to you. :) I build up the HV circuit as well now and so far its working great.
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