Playing with IC’s: Part 3
In Part 2- https://www.jestineyong.com/playing-with-ics-part-2/, I thought I had received some damaged IC’s because they were not working right. Then our friend Steven Neo suggested that I had the inductor in the circuit wrong. Of course – that is probably the problem! I can’t believe I didn’t notice my mistake, but I am glad Steven did. As it turns out, Steven is correct.
So I rearranged the circuit on the breadboard while also bringing the components in closer to the IC. Eureka; the IC is working properly now!
Here is the Datasheet for the IC #FR9882: http://pdf.datasheetarchive.com/indexerfiles/Datasheets-AS2/DSAAXSA0008861.pdf
As you can see in the next few photos, the IC is outputting acceptable voltage at different input voltages – problem solved! This IC is working properly even on my breadboard! I decided not to build the circuit on a PCB, at least for now.
The IC is holding strong at an input of 8.16V.
I checked two more IC’s and they checked out good as the first one. I know for sure that one of them is bad, but I’m not going to show everyone of the IC’s in this article. I will find the bad IC’s later and throw them away. Testing three of the IC’s is enough to prove that my circuit was the previous problem, and not the IC’s being shipped to me without ESD protection.
The IC is still holding strong at 12.07V input!
Here is a snapshot of one of the IC’s waveform. It has a frequency of about 315 KHz, which is in tolerance for the IC.
There is a secret I learned on a YouTube channel that I’m subscribed to. The channel is named, “Mr. Carlson’s Lab”. Mr. Carlson is very knowledgeable and has many great electronics videos. I advise everyone to visit his channel and subscribe. https://www.youtube.com/user/MrCarlsonsLab
I have always heard that “non-polarized” capacitors are non-polarized, haven’t you? Well, as I’m about to show you, that is not entirely accurate…
In the Poly or Mylar type capacitors, one of the leads will be connected to the outside foil end (Band End), or also called the (shielded end), or (foiled end), of the inside of the cap. The lead that is connected to the band end of the cap should be connected to ground, or the lower impedance of the circuit, depending on the circuit the cap is in. If the band end is connected to the higher impedance in the circuit, then it will emit RFI that can couple into surrounding circuits! It can also give you a hum or noise in amplifiers! If you have replaced caps in radios or amplifiers and had noise that should not be there, then you may have installed the “non-polarized” capacitors in backwards!
In the following photos I will show you how to check your caps so that you will know which end is the band end (shielded end), and install your caps correctly! Of course, RFI doesn’t make much difference in my little test circuit here; but it can make a lot of difference in other circuits!
In the above photo you can see me holding the 10nF cap in the photo above this one in my fingers (without touching the leads). My body is acting as an antenna. I have a coax cable connected to my scope on channel 1. The scope is set to DC 2mV/div at 10ms/div with the 20MHz BW Limit on. I previously checked the cap and marked the band end lead with a red marker. The positive grabber on my coax is connected to the band end of the cap, and you can see the size of the waveform. So the waveform should be smaller when the negative or ground lead is connected to the band end because my body, acting like an antenna, will have less effect than when I’m holding the cap this way because the band end of the cap will help shield the current passing through the cap.
So when you have the smallest waveform, the lead that the ground wire of your coax is connected to, is the band end, or shielded end of the capacitor!
You can see in the above photo that the waveform is smaller now that I have the coax connected properly; with the ground on the band end lead of the cap. Be careful not to touch the leads while holding the capacitor.
I also noticed that resting my elbows on my grounded anti-static mat on my table affected the readings, so be careful. It is also harder to tell the difference on the real small caps.
The waveform is larger in this photo indicating that the ground (black) grabber is not connected to the band end of the capacitor.
On this second capacitor in the two photos above, you can clearly see that the bottom lead is connected to the band end of the cap because when the ground lead of the coax is connected to it, the waveform is smaller.
Now you can go fix problems that others could not fix! And you can install your caps correctly in your own devices so they operate more efficiently with less RFI emission!
Also be careful because some caps will have a mark on them, but it will NOT necessarily be the band end! So you can check them yourself now to be sure!
And many caps in the same batch will have the numbers stamped on different sides of the cap, so that if the band end of one cap is on the right side when reading the information on the cap, another one may have the band end on the left side while looking at it. So check them yourself to be sure. Here is a link to Mr. Carlson’s video about this secret: https://youtu.be/BnR_DLd1PDI
New breadboard with the inductor in properly, and the components moved in closer to the IC.
Notice the arrow in the above photo? I accidently had the cathode of the 22uF electrolytic cap (C2) in the positive rail instead of the negative rail. There is no power on the positive rail, but it rendered the cap useless for the circuit. That is why I was only getting nearly 3.2V output from the IC, and a distorted waveform. Once I corrected that mistake, the IC’s performed beautifully on my breadboard! No need for building the circuit on a PCB for testing now!
Another look at the breadboard circuit.
Here is another look at the breadboards.
Here’s a sneak peek into my new BK Precision 114a VOM. It is a quality meter! Praise the Lord God – I am very fortunate to buy it at such a great price! It also has a good ceramic fuse.
The above photo is an early one with the cathode of the 22uF cap (C2) in the positive rail instead of the negative rail where it belongs. You can see the distorted waveform and the lower output at 3.143V.
I’m almost sad that I am finished with this article. Oh well, time to move on. I hope you guys like the article. I would like to give special thanks to Mr. Yong for providing this website for us to learn, share, and experiment. Also, to Mr. Carlson’s Lab for his brilliant videos and revealing of great electronics secrets. And thanks also to Steven Neo who spotted my mistake and made for a swifter end to the article. Thanks to all who comment and support our articles.
Robert Calk is a hobbyist from the USA that loves learning electronics and device repair.
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