0071 - Let's Polish This TURD!: FG-100 DDS Function Generator FIX
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- čas přidán 5. 07. 2023
- In this video we'll attempt to fix the FG-100 Function Generator by replacing the fake TL074 op amps with genuine N5532 unit. It did not quite go as planned.
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Function Generator: www.aliexpress.com/item/10050... - Věda a technologie
I, like yourself, have an uncanny ability to turn a 20 minute job into a two hour adventure.
LOL!
Nice! Not a bad generator if it works as intended. Thanks for the follow-up! 👍
It does work pretty well once it has good op amps in it. I wonder how much they are saving by using parts that literally don't work?
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.
Give it a go! Those SOIC packages are not super small. Removing the ICs is possible with lots of fresh solder and a chunky iron. Then clean up with solder wick and some flux. Soldering SIOCs is doable, even with a big iron. Use flux when soldering and remove any bridges with wick. I’ve had several eye operations, have shakey hands and can still do 0.5 mm 64 pin LQFP with ease. 🥳 If you get it to work you have a generator, if not you have gained some practice 🌞
As trcwm suggests give it a try. As it stands now you have an unusable chunk of junk. The worst that can happen is that you get some experience and loose $3 on new op amps.
@ 3:25 Why not a few pieces of kapton tape and use a smd hot air torch
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.
Yeah, for dual supply purposes I'm a fan of the NE5532 as well. It's a better spec op-amp than the TL072 and available from reputable suppliers for just a few cents more even if you can find genuine TL072s anymore.
Yep it's a great performer for Audio projects@@uni-byte
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
This is most likely normal behavior. It sounds like you have the scope set up for DC coupling and the offset on the function generator is on and not at null. Is this correct? Also, does the signal on teh oscilloscope look like a good sine wave?
Try setting the oscilloscope to AC coupling.
Or, try setting the DC offset to off (push the top red button in)
Or, try adjusting the DC offset until vMax=vMin.
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.
Yeah, mine was a poor copy for sure. Good the hear you got a working one and it's probably an original.
Thanks for the comment!
I just bought one from Temu and it works great. Maybe the factory fixed the problem.
Thanks for sharing and good to hear you got a good one. Your vendor may have got them from a more honest factory. These are being built by multiple manufacturers.
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.
You could use this FG to generate the carrier frequency then use that as one input to an external modulator circuit (a simple J-FET circuit could do it) and the amplified audio as the modulation input. Do a google search on "How to make an amplitude modulated wave". As to tone generation, it does that anyway. Just select the frequency you want and turn on the output.
@@uni-byte thanks very much for the reply, I will try that!
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.
You would need the battery, a BMS module and a boost module to get the required voltage. It would very difficult to fit any regularly shaped battery and all that other stuff in the stock case. I would suggest making an add-on case that attaches to the back to hold the battery and circuitry.
@@uni-byteor you can use a cellphone power bank instead, it has a 5v output, it's rechargeable and possibly can find one with the same form factor as the generator itself.
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.
Right about the beginning of June when I did the first video on it. You should check that out if you have not already. There is a link in the description above.
@@uni-byte Weird. You might have gotten some old stock since you have the DIP socket with the Atmel. Mine works decently with square wave up until 80-90kHz, but the microcontroller seems some Chinese clone because the pinout is different. I'm pretty disappointed because I wanted to reprogram it to support adjustable duty cycle.
I don't think mine is old stock, just a bad clone with fake op-amps. There may indeed be a newer version or alternative versions but I'll bet that there are many manufacturers of this device.
The JYE Tech FG085 is a much better Function Generator. Your thoughts?
This one is not bad when the op-amps are good ones. The FG085 seems to have a better user interface and can do a lot more. But then again, you pay quite a bit more for it so it should be considerably better.
i have the same function generator, but it doesn`t generate any wave at all :(
That's not good! In the first video I show where you can scope to see if the microcontroller is producing an output before going to the amplifiers. If yours has a signal there then replacing the op-amps will likely fix it.
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.
Yeah, that's how it's supposed to work. The pads that came off actually broke when I was cutting other leads. To be honest, this is the first time I had the problem.
Why did you not use a hot air gun?
I think I mentioned that some where. It was going to be difficult to isolate the hot air to just the op-amps. Too much danger of peripheral damage.
@@uni-byte I see where you are getting at. Better safe than sorry.
@@saydmarschany8321 Precisely.
You must have like many others have gotten a bad one because mine works just fine.
I guess you "pay your money, you take your chances" applies here. If you don't mind me asking where did you get yours and what was the price?
Fake TL072, ....THAT's CRAZY, ....but I bought 500 fake LM358, yet 200 ADR8628 at 20c each were genuine ....GO FIGURE!
Yeah, TL072's are just about the cheapest op amps around. How much more would it have cast them to get real parts? I know I said TL074 in video (nice catch BTW) but I was thinking if they had gone to using a single TL074 they would probably have saved as much as they did by using fakes.