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Electronics => Beginners => Topic started by: duckduck on April 15, 2021, 05:54:26 pm

Title: Should I power a device with the leads hooked up backwards on the power supply?
Post by: duckduck on April 15, 2021, 05:54:26 pm
POP!

No. No, I should not.

EDIT:

So, to further publicly humiliate myself. I should mention that this is the SECOND one of these ICL8038-based signal generators that I have accidentally destroyed using this method. The first one I put down to "damn cheap crap off of Amazon". In both cases I ignored the warning flag of the amperage ramping up scary fast as I rolled up the supply voltage to the spec of 12-15 volts DC. Turns out a small IC and supporting components doesn't consume 2,000mA @ 12V. Who knew?

I swapped the leads on the power supply (noting the handy + and - symbols printed above the terminals) and, amazingly, the signal generator outputs a nice square wave. The sine wave had a triangular top but seemed kinda OK otherwise. I've ordered a third one.  :palm:

EDIT EDIT:

You often learn valuable lessons from your mistakes!

Indeed, nothing like a good old-fashioned public shaming to burn that lesson in. If I can serve as a negative example and/or reminder to others, so much the better.

EDIT EDIT EDIT:

Now I where saftey glasses ,  double check and look away on first power up when ever a cap is changed .

Yes, that cap cap shot up like a little bullet. I'm going to leave a pair of safety glasses at my electronics desk. Thanks for the suggestion.
Title: Re: Should I power a device with the leads hooked up backwards on the power supply?
Post by: harerod on April 15, 2021, 06:11:39 pm
R5 seems to have gone high impedance...
Title: Re: Should I power a device with the leads hooked up backwards on the power supply?
Post by: schmitt trigger on April 15, 2021, 06:20:32 pm
Were you able to catch some of the magic smoke before it flew away?
Title: Re: Should I power a device with the leads hooked up backwards on the power supply?
Post by: bobbydazzler on April 15, 2021, 10:46:14 pm
Did R5 melt?
Title: Re: Should I power a device with the leads hooked up backwards on the power supply?
Post by: srb1954 on April 15, 2021, 11:31:44 pm
You often learn valuable lessons from your mistakes!

The shock of an electrolytic capacitor exploding in your face is the best way to learn that you always need to check the polarity of your power supply leads before switching on.
Title: Re: Should I power a device with the leads hooked up backwards on the power supply?
Post by: ledtester on April 16, 2021, 02:05:41 am
This XR2206 kit has a diode, but I don't think it was drawn correctly in the schematic:

[attach=1]

More details:

- https://rhelectronics.net/store/function-generator-xr2206-diy-kit-20hz-100khz.html
- Kit PDF manual: https://ln.sync.com/dl/80dc9e630/9u9yqjmr-72bk4qs8-93geqv9y-td7zxkfa
Title: Re: Should I power a device with the leads hooked up backwards on the power supply?
Post by: Ed.Kloonk on April 16, 2021, 03:02:25 am
Were you able to catch some of the magic smoke before it flew away?

Have you ever noticed that the eye socket is the perfect size and shape for catching flying capacitors? Hold the tongue right.
Title: Re: Should I power a device with the leads hooked up backwards on the power supply?
Post by: Jwillis on April 16, 2021, 04:37:23 am
Have you ever noticed that the eye socket is the perfect size and shape for catching flying capacitors? Hold the tongue right.

I know all about that . I had a 13 x 25mm blew off the board like a bullet and struck me just on the lower edge of the left eye socket . Doctor said that if it was 5mm higher I would have lost the eye . Now theirs a permanent scare where the stitches were and I lost some peripheral vision .

Cause was an incorrect polarity . Now I where saftey glasses ,  double check and look away on first power up when ever a cap is changed .

Please be careful .