Uni-Byte 0071 - Let's Polish This TURD!: FG-100 DDS Function Generator FIX

In this video we'll attempt to fix the FG-100 Function Generator by replacing the fake TL072 op amps with genuine N5532 unit. It did not quite go as planned.

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[GamingKeenBeaner]

We just ordered the newer model, the FG-200. I'm eager to get it and see how it varies from your model. There's almost no reviews of it in English yet.

[trcwm]

Nice! Not a bad generator if it works as intended. Thanks for the follow-up! 👍

[dryster]

I, like yourself, have an uncanny ability to turn a 20 minute job into a two hour adventure.

[mirzakral]

Is it possible to build an oscillator circuit, drive it into the ground through two electrodes, and emit electromagnetic waves at desired frequencies?

[zenbum]

Congratulations, you successfully polished a turd. I'm impressed!
I bought one of these units on Amazon, hoping it would be "good enough". It wasn't. I had almost exactly the same symptoms as you. Unfortunately, unlike you, I have neither the patience nor the eyesight to replace the bogus SMD chips.
Thanks for the video.

[andymouse]

Nice set of videos, very enjoyable. I nearly bought one of theses a few years back but I have mixed feelings now ! besides I have something better. I'm a massive NE5532 fanboy so that was nice to see and the outputs are quite usable now at 1v PK-PK. The IC was a cow because you were filming it so Sod's Law ! it's a shame buying this stuff is such a damn lottery but like you say you gotta roll the die and see what happens...cheers.

[radioflyer]

Have you ever tried considered "low melt" solder (FastChip removal alloy for SMD)??? This stuff is MAGIC, and it really makes getting tiny things off of PCBs much easier. It stays liquid, or the consistency of warm cheese for 10-20 seconds after removing the heat. Use a wide chisel tip, or take a narrow tip & bend it like the shape of a hocky stick. Melt low-melt solder onto the 4 pins on one side of the chip, then the other side, then jump back & warm the first side again. With a bit of practice, the chip will just slide off the board. Works for about up to 8 pins per side, perfect for op amps & modern audio circuitry. Also step up your flux game with something like Amtech 559 - it's a bit sticky & harder to clean off, but solder goes where you want it, and stays there until it hardens. Also, solder comes out of holes when using wick much better after adding some 559 - it really improves solder flow beyond what I thought was possible. These two things turned my SMD work from disasters to "hey, I can do this!". I don't care much for the expression "game changer", but it sure was for me.

Regarding the FG-100... do you have any suggestions on how to tame the amplitude down so that it ranges from 0 to perhaps 2v, max 3v, and the range is smooth & controllable?? I just need it for quick tests on commercial audio amps, and it is just waaaay too much output for my use case, and the area / arc of rotation on the amplitude pot that does suit my use case is so tiny as to be uncontrollable in actual use.

[saydmarschany]

Hi, like your video. Absorbed a lot of info. Would it be possible to make a modification to this unit and add an interior lithium battery to make it portable? Thank you.

[narendradc]

Thanks for your videos. I purchased this one from amazon. I have set sine wave to 100Hz and Amplitute to 4.63v. My oscilloscope shows vMax = 0.98 and vMin = -3.57. Do you think my device is defective? I appreciate for your answer

[ScottieWallace]

Hi I have the updated version of this function generator, I am wondering, would you know a simple way to connect a microphone somehow and use an antenna to send a voice message over a specific frequency please? Also do you know a way to make it output tones? Thanks in advance if you had the time.

[ooltimu]

When did you buy this unit? I also bought 3pcs a month ago and they came with a QFN32 unmarked chip. Pinout is similar to an Atmel, but it is different.

[shlomsi]

Thanks for the video,
I too have this unit bought many years ago, operates just fine, all screws mounted,
The PCB looks just the same, but has a silk printing on the top left "FG-100_v1.1"
2013.10.29 probably manufacture date, so I guess you have a clone of a clone...
op-amps are tl072c, but I have no way to know if genuine or not.

[MsFireboy]

The JYE Tech FG085 is a much better Function Generator. Your thoughts?

[TheCrunchbird]

I just bought one from Temu and it works great. Maybe the factory fixed the problem.

[AhmedBadr-ct]

i have the same function generator, but it doesn`t generate any wave at all :(

[td]

Not finding fault with your cutting happenstance, but here's some cutting information... The side cutters that you have are what we all use. Their blades have very particular technology incorporated into them (even the cheap ones.) I will leave it to the individual to research the entirety of the subject, but what is of interest, in this cutting application, is the grind of the blade... The blade is only ground to one side. Let's cut a pin, to explain... You put the (flat) bottom of the blade on top of the pin's solder joint (above the PCB board) and snip the pin. The angle of the grind of the blade forces the pin upward. No force goes downward. This protects the solder joint from mechanical stress. So, you may have more success by taking care to orient the blade angle to push the pins back against the body of the IC. Meaning, the flat side of the cutter's blade would be facing the trace's pad. However, a cheap board is a cheap board. And, no reasonable amount of care will make up for that. There are many more blade features to discover, like the fact that the blades are intentionally offset, in the vertical plane. Cheers.

[gordselectronicshobby]

You must have like many others have gotten a bad one because mine works just fine.

[stevenbliss]

Fake TL072, ....THAT's CRAZY, ....but I bought 500 fake LM358, yet 200 ADR8628 at 20c each were genuine ....GO FIGURE!