really a very detailed and complete review with solutions and again an example how good original electronics get messed up and quality undermined by the chinese vendors trying to compete on price. You have shown the world with a little engineering to get right. Thanks again since I have this original XR 2206 function generator from more then 20 years. Not surprisingly it still works. It is fun to see this Exar Co. survived all the turmoil and that the Chinese still can make a few buck with their name. Thanks again Kainka. We need this sort of review.

I hooked my XR2206 eBay Function Generator up to my scope, and observed a bunch of weird problems. I went searching for information about this, found this video, and experienced the most efficient 38 minutes of electronics schooling I've ever had. Thank you, sir!

Your schematics are gorgeous. Thank you again for going even beyond what is needed to make this thing work. I love tweaks. The closer it is to optimal, the more I like it. You did all the hard work. KainkaLabs, give this man a raise.

This sets you apart from the rest when you come up with the fixes to correct something and make it better thank you

thanks for the two videos. Very detailed. I had also bough the same kit. I just wanted some function generator for playing around, but even the sine wave did not look that clean to me. So I bought a used GW instek for a little bit more. Didn't realize all the problems you showed. Very nice.

Excellent debug of this unit! I built quite a lot of 2206 chipped oscillator units for the Audio recording studios I worked at. These had 5 fixed sine wave frequencys selected by rotary switch in order to set up analog 24 track tape machines for Bias, record levels and playback tones. Original EXAR data sheet seemed spot on for the low frequencies 50hz~20Khz sine wave used. This Ebay unit looks good after your work!

This material is educational GOLD. Your descriptions are easy to follow and academically dense. Subscribed and liked. Awesome. Jonathan in Seattle.

I bought one for audio applications and this video is pure gold

I'm glad I found you. My sinewave as you have shown was a bit distorted. I'm gonna do your method of repair. Thanks from Australia🙂

Thanks Kainkalabs. (ROGER). This was very helpfull. :). I made the functiongenerator with the options you give me. Right from the start. Thank you very much. Paul from the Netherlands.

Thanks a lot. Very useful information and a little kind of work that an engineer must do when a problem is on the road. At company I work I see this kinds of troubles when a cost reduction is implemented on products we manufactures. Best is to buy to OEM ICs ever.

Daniel from Ireland. You are a HERO!! Thank You.

Good rundown of the problems and solutions for this circuit. Two areas I would disagree on: 1. I don't like the idea of using input protection diodes to compensate for driving logic with too high a voltage. As you suggest to an earlier comment, a voltage divider would be the easiest fix although a proper level shifter would be better 2. It seems unlikely that the real XR2206 would improve the output square wave at high frequency with a 10K for R1. The output is open collector and the slow rise time is due to the RC time constant formed by R1 and whatever is connected to the square wave output (including parasitic capacitances). If the real XR2206 really is better, this suggests large stray capacitance in the fake part.

Wow, pretty cool. Thank you (and the people who gave you some feedback on various issues) for this. I just bought one and will definitely be double checking everything. I bought the thing mostly for 1)improving my soldering skills, 2)testing a soldering station I bought as a present for my dad and 3)I will use this a wave generator for a basic synthesizer I would like to build to learn more about this type of instrument. For this purpose I want to go as low as possible in terms of voltage and also cover 20Hz - 20kHz. I guess as usual it is safe to assume that there is a 99% chance for an IC to be fake when it's shipped on Amazon, eBay, Aliexpress etc. from China. :D No surprise there.

Awesome. This is super helpful, and I can now use this generator to test tube amplifiers that I build!

Great vid on this oscillator, it's a perfect fix, thanks! One suggestion i have would be to connect a 100k resistor from C10 negative to ground. This will keep the C10 capacitor charged during operation, thus keeping the DC off of the output at all times. The 100k will have negligible effect on output loading.

I notice theres no mention whatsoever on the one page info sheet of the need or function and their freq coverage of the five pairs of paired header pins. Also mine too has no brand logo on the IC itself, just ordered a branded replacement. Thanks for posting this, an excellent way to learn practical electronics.

Thanks for the videos. I still have my kit in the original package that I got a few weeks ago. I'll have to open it up and see if they made any changes to it. I kind of figured that the chip was a fake since the same kit with the case cost me $2.83 US dollars delivered. I always build these Chinese kits on a breadboard first to make sure they work as advertised or to test my own mods to the kits.

Thank you for the video! I am finally getting around to building my kit. Ideas: 1) I will be using individual socket pins, cut from strips, for the discrete components that can be changed within a range of values to tweak the performance of the circuit. 2) A followup video about any new thoughts that you have about the project would be great. 3) Adding closeup photographs of your adaptations to that video would be very helpful to us, to devise our own configurations. If you are not interested in creating a new video, maybe you could take individual photographs of the said adaptations, post them somewhere and give us the link to them. Please and thank you.

Thank you for your hard work! I bought this little cheap kit to help me learn how to solder. Got it "working." Now I am using it to help me learn how to DESOLDER! 😂I will come back and try to test some of this out on my breadboard once I get the parts out.

Very good explanation and useful information thanks for sharing, I will check this out tomorrow and make some changes.

An excellent and very informative presentation. Thanks very much!

This was very useful. I've swapped R3 R5 and the amplitude is much more useful. Just need to get the A10K pot now and I can fix the rotation too.

Many thanks for this and the earlier video. I have just bought one of these kits and after the initial jubilation of it "working" started to notice all the issues you mention. The one that is really bugging me is the frequency instability. With the chip I have I can't find any supply voltage that gives an acceptable level of stability. So I am now out looking for an original part that I can get in the UK. Still at least I know what the problem is. So thanks again.

Thanks! Very interesting the subject made available.

Thank You for giving the fixes

Thanks Great video !!! Very detailed. I'm buying one now..

By the way THANK YOU FOR A VERY INSTRUCTIVE/ INFORMATIVE VIDEO !!!

Wow, good catch ! Many of these generators were sold as 9v dc powered generators.

Very informative thank you, great tutorial

Great video and explanation. ( good sleuthing "Daniel from Ireland" )

from the image of the pub in your video it looks like you have C9 soldered to the side of the barrel power plug for the negative connection which I also did. I also ordered a genuine XR2206 from Jameco just to compare the results.

Counterfeit components on EBAY? Who would have thought that? Thanks for an interesting video, I live in SE Asia so it'll be difficult to find an original chip. We have counterfeits of everything from chips to Toyota vans (no joking).

Great analysis! I will try to build mine accordingly. There is just one problem. The JYE-Tech DSO150 I have yet to build wont help me adjusting the gain control. Is there a useful fixed restistor value for R4 that I could use?

6 years later and this is still incredibly helpful! Thank you so much for the time and effort you put into this. Tracking down components for the upgrade now!

Hi, Thanks for the very complete and comprehensive videos! I also found another issue that is wonder is somebody else had: In my signal generator the maximum possible amplitude is around 3.5 volts (peak-peak) and no matter what I do stays the same. I changed the amplitude potentiometer for a larger one but the issue persists. Any hint of what could be the cause? Thanks!

Круто! Я то думал -- почему у меня xr2206 не работает... Спасибо за рецепты! Буду пробовать))

Did you actually try the authentic XR2206 chip with regard to the square wave output issue? Because that is exactly what you should expect to see as you vary the pull-up with an open-collector/open-drain output. Your scope input is presenting a capacitive load which the pull-up resistor has to drive, so the higher the resistor value, the longer the time-constant. The reason it appears to be frequency dependant is that you are changing the timebase on your scope and just looking closer and closer at the rising edge. Note that the falling edge is not effected because the output drive transistor determines this, not the pull-up. A better way to condition the signal for lower voltage logic would be to replace the simple pull-up with a voltage divider so that the peak voltage is limited by the voltage divider ratio. The effective R with respect to the RC time constant then becomes the _parallel_ equivalent of the two divider resistors (Yes, even though they are in series with respect to the supply, they are in parallel with respect to the output) This will substantially lower the RC time constant, and improve the rise-time. Also you will not be relying on the digital circuit's input protection diodes to limit the voltage, so the input current limit on the digital logic is moot.

Very informative thank you

Great video! i was wondering if you have played around with the fm pin on this IC chip. I was considering using this board to make a sweep generator.

thank you very much sir..

0918, and 0919 seem to be the magic numbers on these currently available Exar chips. I initially bought a couple on eBay two years back and a recent one from Tayda (all say F0918). I still have a hard time believing that Exar suddenly puked out a billion of them in two specific months despite being in production for so many years. FWIW, I didn't seem to have the voltage issues with mine, but I couldn't get an op-amp based virtual ground to work without losing the negative side of my output wave. Could have been the circuit, but it came from a schematic which was mass produced as a kit, so I'd imagine someone had a working one somewhere. - and thanks for the great videos!

The Amplitude VariableResistor is also reversed. Turn rigth amplitude decrease, turn left amplitude rise. The coarse and fine variableresiator are fine. We modify the pcb trace to fix the amplitude variableresistor issue. And The 10KOhm rv09 variable resistors are not available here, so just use the original 50k one in parallel with 12KOhm or 13KOhm resistor. Thankyou uncle Rogers. Bye bye from village labs..:)

Very nice and informative video indeed. Many thanks. Just a question though, which minimum frequency could you get to in "square wave" mode?. Is it really possible to get down to below 10Hz?

well explained with real test thanks

Hello, Thanks for all your incredible work on this fix. For some reason I can't access the link in description for fix. Do you have an alternate link I could download instructions for fix please?

Hi, Roger! Thank you so much for this video...it was extremely informative! I especially liked your improvements, and the schematics you provided with the changes. I made all of the modifications you suggested, and they all worked except for wiring R7 (changed to 10MOhm) and R8 in parallel. I may have mis-wired the pots, but changing R7 didn't seem to make any difference. I reverted back to R7 and R8 in series and it works well enough. Also, I replaced the supplied/fake XR2206 with a genuine XR2206 and it seems to work better, but I still have very narrow noise spikes at the maximum and minimum of the sine wave. The spikes are present with both the genuine and fake XR2206 chips, so I wonder if the problem is being caused by another component (one of the caps)? Also, I was able to source all of the replacement components from Jameco (in the US) for $11.73 (including a genuine Exar XR2206). Not a bad price for a significant upgrade! (I will make a separate post with the Jameco part numbers and prices.)

I am a bit late to this party, but I learned a lot from your video and will apply these improvements to the kit I bought online. I was curious if you have also looked at the 8038 kit(s) that are out there? I bought the one that comes with the acrylic case, but am quite disappointed in it. The problems are so numerous that I doubt I will even attempt correcting them. However, there are a few other 8038 based kits, so I may try one of those as well. I'm looking at these more from a learning perspective than an actual user perspective (although I definitely will use both of them). Thanx again for some great videos.

good information, the link for the schematics and optimized components list does not work.

Hi, just a quick question, I'm ready to assemble the kit and I'll implement all your suggestions with the exceptions of using the fake IC and for R2, I'll use a 10K linear pot (which I already have). Will there be any negative effect to my output due to those deviations? Do I need to change the connection of the wiper like in your diagram having a linear pot in R2?

Hi, I try to find the authentic XR-2206 but can't find one. So have you got any suggestions for me to get the real one? Many thanks for this helpful video!

Excellent. Thank you. Is there any reason that R1 could not a be minimum 1K Ohms and a 10K pot added to it in series, so that the sum of R1 could be trimmed on-the-fly, as the frequency requires?

It's good that you showed the difference between original XR 2206 chip and the "fake Chinese chip". I wouldn't want to rely on Chinese chips if I don't have to.

Good day. I am thrilled with your instructive video. I had the above kit with XR2206 so I decided to apply all your recommendations. BUT BUT....I have some problems. 1. I can't regulate the amplitude at all. It's at maximum. 2. I don't have SINUS and TRIANGL signal shapes at the output. I only have a rectangular signal. Trying to adjust THD using trimpot R9 and R4, at the output for SIN and TRIANGLE I have a square shape with rounded edges. The supply voltage is 12V. The XR is Chinese.

Another possible solution to the square wave problem is to keep the 1K resistor and clamp the output with a 5.1v Zener diode. I have one of these kits but not built it yet, so I may try that as many 3.3v logic devices are 5v tolerant these days, I just don't know if a Zener would be fast enough at higher frequencies.

HI There, Very good explanation and testing, thank you. Is it actually be set as positive offset frequency?

There is an error in the Exar data sheet where it says that the output amplitude is 'inversely' proportional to the value of R3 where it is actually proportional to it (see figure 3). This is probably caused the amplitude pot reversal mistake by the PCB designer. Its function is to 'rob' the output pair of some bias and thus their gain. The manufacturers have also fixed the mounting screw issue by resizing and now use short screws and nuts as a PCB resting platform. As the XR-2206 was designed in the 70s, it is likely that its IP has been passed on so it shouldn't come as a surprise that the Chinese are now using it.

Great video! Is there a way to do phase shift for this one? Say I have two of these and want one of the two shift 90 degree.

I love your work with this chip. After making these changes, have you thought about a way to make it sweep from one frequency to another ? I have a need (radio testing) to make it sweep from about 200 hz to 5000hz and be able to view it with an oscilloscope.

I noticed that in your video comparing the DSO138 scope that your scope and numeric values on the screen with PPV and others. Mine does not. I built it from a kit approximately one year ago. I believe the software is upgradable and so I hope that I can add these features. Also, do you have a way to receive donations to help support your video making? It is tough to continue and I know that some whom I like take Pay Pal contributions. Thank you, Roger!

Thank you soooooo much

Very good explanation. I made some changes you suggested and works like a charm. Only problem is that square wave amplitud is not adjustable. Can you make a high frequency (up to 500KHz) Amplitud control for the square wave?

Why not connect a high value resistor at the output to help discharge C10?

Thanks for this video, KainkaLabs. I put together this kit and followed your improvements. The square wave looks good even at high frequency but I find that the sine/triangle output has an offset of a couple of volts which does not seem reasonable. Has anyone else had this?

Roger, I have watched and enjoyed both of your videos about the XR-2206 Function Generator. Have fried my IC by inserting it upside down... I order new IC's (the old IC had markings scratched out). With your improvements and suggestions, I am considering making a board that takes your improvements into account and does not require use of modify parts or using SMD components. I was able to find on Amazon pots of the correct form factor in both 25k ohm & 1 Meg ohm. I will let you know when I have the new boards... and send you one if you like. Thanks again for you good work and analysis to make this a better tool for us hobbists.

I wonder if it is worthwhile to redesign a new pcb with your modifications?

Hi, which would you recommend, this fun-gen or the avr based one?

Hi Roger!!

Long ago, I had read that Exar had gone the way of the DoDo Bird. I was quite distraught because I loved their products, yet I didn't actually research it. Finding that they are still around really made my year. I was wondering though - are those ceramic caps or tantalum? If ceramic they could cause problems in such a circuit since the piezoelectric effect of ceramic makes them microphonic which could introduce noise into the circuit. Then again, I could be completely off base here.

The datasheet shows the output impedance of the sine/triangle output as 600R. Why not just add a 1K (or thereabouts) resistor between your new C10 and ground and stop worrying about the time it takes to charge C10? You can then pick a value for C10 to suit that resistor for the lowest frequency that you're interested in. If you have the fine and coarse frequency adjustment pots in series, then the relative effect of the fine pot increases when the coarse pot is set to a low value. However, if you have the fine and coarse frequency adjustment pots in parallel, then the relative effect of the fine pot _decreases_ when the coarse pot is set to a low value. It's just swings-and-roundabouts and there's no "win" to be had - just a difference in preference.

Nice video. I’m curious... What is the minimum input voltage required to produce a sine wave with 1.5V peak to peak? Thanks.

This is a great Video. I have one question regarding your second change (Swap R3/R5 from 5k1 to 1k): Both form a voltage divider with 1/2 Vcc output. Only the current changes (10k2 vs. 2k resistance in total). I don't understand this change. I would very apricate an explanation :)

The 10K pullup limits the current of the 10V square wave, but what can I do to also limit the voltage to 5V. Only having a 5V max sq wave makes things easier, as I won't have to jump from 10V to my regular 5V all the time.

Thank-you!!!! When I first began learning electronics I came across a super simple circuit of two LED's in parallel but flipped in opposite directions. It called for applying an AC Sinewave which would alternate the flashing of each LED. My oscilloscope had a function generator BUT the sinewave's voltage output was so low it couldn't power on an LED. So I bought this same cheapo XR2206 but was once again disappointed in that it would only light one LED solid but the other LED stayed off. As per your suggestion, I added a 100uF Capacitor to the output AND NOW both LED's flash as expected and I can even adjust the frequency!! Can someone explain why adding the 100uF capacitor solved my issue??

Forgive my ignorance as I'm new to electronics. I want to replace R4 with the suggested 500 ohm trim pot but am uncertain as to the routing of the pins. Trim pot with three, resistor location accepting 2. Do I put the first pin in hole 1 and then extend the wiper pin into hole 2, deleting the 3rd pin on trim pot?

Hi Roger, Is there an English version of your improved schematic documentation?

I wish you would show how you switched the conetions on the amplitude mod zoomed in with c9 ???

thanks!!

Hallo, Thank you so much for a very well explained and useful review. I am trying to modify my function generator kit as per your recommendations but I am having difficulty in finding R2 (10 - 25K Ohm logarithmic potentiometer) having the same form-factor as the original R2 (to be replaced). In your video, I see that you did find one with the right form-factor. May I request you to name the source and/or order number from where you procured your potentiometer, please? I believe that you originate from Germany, I am also located in Germany. So if you could kindly provide me with the requested information that would be very helpful for me. Many thanks in advance and best regards.

It would be helpful if you could post a picture of C9 & R2...but I do not think that you can do this on YT... unfortunately

Great I just ordered that kit ,where can get the newer chip.

there is somewhere that we can buy it with the improvements? good job wek done

Is it possible in XR2206 to adjust the amplitude on the form of a meander?

Hi. Can I just replace R2 for a multiturn pot with the same value?? the lowest value will be ok for 10 mV with this? I am working with audio.

@21:15. YES!! That's what I can work with. Thanks Roger. I will let you know when I get my kit if the XR2206 is counterfeit. The date didn't indicate a fake. What is the difference in logo. If you show it in this video, please disregard. I can probably google the logo. (?) :-)

Can't find your updated schematics etc

What is your source for the 10K logarithmic potentiometers in this form factor? I built the circuit as you have shown and I suspect that the the 10K pots which I had on hand may be a problem. I have no amplitude control and I used an audio-taper potentiometer there at R2. My circuit is working for the square wave setting and I can adjust fine and coarse frequency very well, but I have no amplitude adjustment at all. However, when I switch to the sin/tri output I have no wave form whatsoever. I am very perplexed. I checked the entire circuit with an ohm-meter and all seems correct. I even swapped the IC and that is not the issue either. I have an unmodified board that works with the deficiencies which I have compared.

i bought a kit and some other "xr2206" chips with different looking print, ebay and amazon, best i can get is a square wave from the kit chip, others just give me flat levels or something that looks like its trying to be a triangle or saw but is truncated to maybe 0.5V. i remember watching your first video and being excited to have a sine. but i have to advise, kit purchasers may be lucky just to get a useless square.

Very good info. How can I make a variable square wave out of my 2206? I need something in the 3Volt region.

What is better XR2206 or ICL8038 as a generator? Are there any developments after the XR2206 or ICL8038 chips for the generator? What do you know about MAX038, is it better ?

Hi Roger, I can't work out how to rewire the amplitude potentiometer. The original schematic has left pin linked to R3/R5 and middle and right pins linked to 2206-3. Your schematic has left and middle pins linked to R3/R5 and right pin linked to 2206-3. So we need to remove middle pin from 2206-3 and link to R3/R5. But how to do that in practice? Isn't it hard wired in the PCB circuit? So I could solder a wire from middle pin to left pin, but how to disconnect middle pin from right pin/2206-3?

Thank you for the very helpful video. Unfortunately I was not able top download your schematics. There seems to be an issue with the link. Can you please check, as I am really interested to try your suggested improvements. Thanks Georg Vietor

Hi Mr. Very good video! I found the same issues with mine that I bought assembled. I was in doubt if it was defective or a design error. You solved the doubts. Thanks! Just one issue: I've tried to download your schematics with optimized components and instructions but received a "The request is blocked" message. Could you please help me with this issue?

Have you tried running this chip with a 10v positive and 10v negative input, rather than positive and ground.

Worth mentioning 100p capacitor is completely below accepted region of 1000p

Very good info, but try using battery as source power and stability problem is gone.

Is it possible to adjust the amplitude of the meander (square signal) on this generator?

Hello. I just got my first multi meter and was doing voltage readings on the XR2206. and was wondering how come when I plug in 12v to the XR2206 it changes to 16v just going through the connector? is there a zener diode limiting it to 16v?

would there be a difference if a use non polarized capacitor for C10 AC coupling?

I connected 12v and got the polarity wrong way round. It fried the c1 capacitor and the xr2206 chip. I replaced the capacitor and chip and it's back up and running. I understand a diode between power barrel tip and positive on c1 capacitor and splice the original track on underside of pcb would offer protection against reverse polarity. Anybody know what would be the best diode with minimal voltage losses after input. Just noticed though that +vcc actually has more than one path through the circuit from power barrel it also goes to r3 and r5 voltage divider on amplitude section also so don't know how to pull it off