Fixing the issues with the XR2206 Function-Generator from EBay

This is follow-up video to • Design errors in an XR... where the design-errors are demonstrated.
Download of the schematics with the optimized components and instructions:
www.ak-modul-b...
Support Roger on Patreon: / kainkalabs
This video is about how to fix them and make a really useable mini function-generator out of the badly designed 7$ Ebay XR-2206 kit.
A user has commented that the used XR-2206 is probably a counterfeit chip.
This is confirmed here live by exchanging the chinese-supplied XR-2206 chip with a genuine one.

[@tonbovee5486]

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.

[@espenbgh2540]

Sorry Tom B., Things are not that simple as being shown, as there is more to. There are two main problems with the XR220 and the one it shares with the Intersil 8038. It's the Square wave resistor - it makes no difference the size as using af resistor "kicks back" into the curcuit. The other problem with the XR2206 comes from the switching across the capacitor. The real switching time is approx. 35 nS but that's not all, it's the loading and discharge cycle that coarse the problems. When the loading cycle nears the top - and before the switching occurs the opening of the transistor is under way - beginning to discharge whike charging which gives a spike or notch in the top and bottom af the triangle that is used to from the sinus. This is all internal and can't be changed from the outside. that was the technical level at the time these curcuit was produced. - Please mark the frequens you are shows - less than 20 KHz where it is hard to observe, with higher frequency it becomes more visible and dominant.The Intersil can produce sien and triangle from subzero til 200 KHz flawless, and if you then take the sinewave and convert af part from this to squarewave, you can build a very nice working functions generator.

[@ozzymandius666]

I would love to see a decapping and reverse engineering of the fake vs the real chips.

[@kluzz]

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!

[@jlucasound]

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.

[@coldfinger459sub0]

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

[@sirclip]

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!

[@steverussell1215]

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.

[@SongsForDamnation]

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

[@t1d100]

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.

[@rbaleksandar]

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.

[@richardkell4888]

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.

[@HazeAnderson]

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.

[@HazeAnderson]

I was able to remove all the components and only destroy one cap in the process! That was a few weeks ago, today I assembled the chip on my breadboard and was able to wire up the Basic Test Circuit detailed in the data sheet for the XR-2206. Next -- finalize a new design, test it out and finally solder components to a blank PCB. Cheers!

[@HazeAnderson]

I finally rebuilt the XR-2206 with new components on a double sided proto-board a few weeks ago! The sine wave doesn't seem to work, but the square and triangle waves will do! All in all this was a very educational journey. 😬👍 (I also built a 4 channel audio mixer to better listen to future oscillators and filters I will be building.)

[@bob4analog]

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.

[@robertoaraiza7434]

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.

[@KainkaLabs]

To be fair the Ebay sellers mention that the circuit works only up to 12 volts. And the XR2206 is not produced any more by EXAR for a long time and genuine/OEM/NOS parts are totally overpriced at Ebay.

[@JCHaywire]

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

[@osmanfb1]

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.

[@sawyer7271]

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

[@davidpyper1688]

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.

[@TheSpace1986]

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!

[@manusoftar]

not even because the url provided doesn't work anymore...

[@KainkaLabs]

New link: 1drv.ms/u/s!AmW9-q-1GZM1ip5wO7uvHpcenfI14g?e=m4TqeJ

[@KainkaLabs]

Link has been changed to the kit in our online-shop where you can also find the documentation. Should work now. Built-manual is only in German until now.

[@KainkaLabs]

Link has been changed to the kit in our online-shop where you can also find the documentation. Should work now. Built-manual is only in German until now.

[@gumbykevbo]

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.

[@KainkaLabs]

Yes, it was a genuine XR2206 from EXAR.

[@rsattahip]

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).

[@michaelwaxter3372]

Dont ever buy seeds from China either. None will germinate.

[@jlucasound]

@@michaelwaxter3372 Or they may grow something really strange and of the wrong "value". Corn beans or asparapeaches. ;-) (Why didn't spell check complain about "asparpeaches"? Oh, there it goes. Phew, I thought maybe that was a real thing! Scary. :-0 Cheers, Mike!

[@dragan3290]

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🙂

[@paulsam9208]

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.

[@sliderulelover]

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.

[@KainkaLabs]

Yeah, but genuine XR2206 are very expensive now and only available NOS on Ebay. Nevertheless below 12V the Chinese counterfeit behaves mainly the same way as the original chip.

[@qolbunsalim5188]

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..:)

[@californiakayaker]

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

[@KainkaLabs]

Yes, 9V is "save". 12V is the maximum supply-voltage for these rip-off XR2206 chips.

[@themaninthesuitcase]

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.

[@jasonbrambach6957]

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.

[@billphillips110]

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??

[@Legg99]

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.

[@jlucasound]

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

[@RexxSchneider]

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.

[@carlosrobertocasemiro2326]

Thanks! Very interesting the subject made available.

[@davidkerr8030]

An excellent and very informative presentation. Thanks very much!

[@nedstar7378]

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

[@jidissafi7413]

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!

[@jidissafi7413]

make that two specific *months*

[@jidissafi7413]

duh- make the months weeks ;-)

[@KainkaLabs]

I think the XR2206 from these Chinese kits must be counterfeit-chips. So you probably can´t rely on the date-code but have to rely on the reputation of the seller if you buy a replacement XR2206. There are some KZbin videos out that the Chinese even fake the 555-timer chips! Someone has decapped them and compared to some original ones and found some obvious differences in the chip-layout :-)

[@jidissafi7413]

KainkaLabs- This recent one was bought as an individual component from Tayda Electronics. I inquired afterward about getting an older one, and they were very helpful and seemed interested in seeing that they weren't buying counterfeits. They said they tried to get 0918, as they had reports of problems with 0919 chips they bought. I just have a weird feeling that, unless someone grabbed a big pile at a government auction or something, anyone who's obtaining enough to be selling them in 2017 is probably getting remakes or we'd be seeing a much wider range of date codes. On the plus side, maybe the Chinese will be tweaking them as more people become aware of the "undesirable qualities". When I checked, mine went up to 18V or something before it got shaky, so it doesn't appear to have that problem.

[@KainkaLabs]

Very interesting. THX for the info.

[@nieuwegeljo5645]

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

[@joemcelvenney7126]

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.

[@KainkaLabs]

Yes. That´s why a picture (graph/diagam) tells more than a thousand words :-)

[@jamesmonaldi6004]

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?

[@KainkaLabs]

Link has been changed to the kit in our online-shop where you can also find the documentation. Should work now. Built-manual is only in German until now.

[@stevec5000]

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

[@KainkaLabs]

That´s a good idea. Haven´t thought about that.

[@fridaynighthikes]

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

[@taixcybersafe]

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

[@justjimjpc]

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.

[@KainkaLabs]

Hi. That is a great idea. Would you be willing to make the PCB-files available for open source? The potentiometers have a standard footprint and are originally from Alps.

[@justjimjpc]

@@KainkaLabs I Have the new board well underway... and have a photo of current configuration (dont think i can post it here ????. I have not yet decided whether to make it open-source or not... but will consider it. By the way, In looking at the XR2206 data-sheet i see that the component values used in the board are what was in an example schematic in the sheet, and were not just pull out of the air. So, they might be ok without changing them if a genuine XR2206 is being used. If you would like a pic of my current version ... just send me an email at [e-mail] (Subject Line XR2206 Enhancement) Stay well and thanks for the reply.

[@judduhre]

That would be awesome!

[@roratoria]

The logo is wrong on the 'fake' (counterfeit) parts. In the 'R' part of the logo, the real parts the curved part of the 'R' is curved. In the fake parts it is made up of all straight lines. Also on the real parts the engraving of the part number is fine where as the counterfeit parts are clearly laser engraved. As logos are tightly controlled this is not a production batch issue.

[@yunkucho]

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?

[@KainkaLabs]

In theory with an adiitional potentiometer at the output of the square wave. 1...10 kOhm resistance value should work.

[@yunkucho]

@@KainkaLabs Thank you for your reply. Based on your theory I implemented with a 5 kOhm potentiometer built-in in the kit and works perfect. For your reference I made this video: kzbin.info/www/bejne/i4GUiGeJqMl4hqs Thank You.

[@robertjorr9]

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.)

[@KainkaLabs]

The spikes at the upper and lower limit of the sine-curve are a consequence of how the sine-wave is created inside the XR2206. It is a well-known bad "property" of the chip. Soon after the chip came out some clever engineers developed some "workarounds" with a lot of extra-circuitry to get rid off or minimize the spikes.

[@robertjorr9]

@@KainkaLabs Ah, that makes sense; thanks for the explanation. After I looked at my board again, I realized that I forgotten to solder in C9, and I thought that might solve the problem. It did stabilize the signal a bit, but didn't get rid of the noise spikes (obviously). The spikes really distort the sine signal badly above ~100kHz. It's notable that the closer you look at the performance of this chip, the more flaws you see (the noise spikes, bad square wave asymmetry below ~100Hz, etc.)!

[@anatolsam6715]

I believe it's more convenient to use only one multi-turn potentiometer instead of two R7 and R8.

[@KainkaLabs]

Yeah, but a 10-turn pot doesn´t fit here. These are 1-turn trimmers and so the combination of a high and low ohmic value is a good and cheap idea, if the value of the 2 trimmers is in a good ratio.

[@DerBullgod]

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?

[@robloxguys0004]

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.

[@KainkaLabs]

I can´t do remote diagnosis. In 99% of all cases it´s a soldering problem. Perhaps you have shorted out 2 pins or not correctly soldered another pin.

[@christiankelly1981]

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

[@KainkaLabs]

You can use any Schottky diode with let´s say >100mA current capability.

[@IanSlothieRolfe]

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.

[@t1d100]

FYI, as of 06/08/2022, Foxfire will not open the English link, even with the https/http correction.

[@timburns9754]

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

[@KainkaLabs]

The minimum *supply-voltage* would be around 4...5 volt, I guess.

[@ademchyshyn]

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

[@t1d100]

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?

[@letrung9199]

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!

[@KainkaLabs]

Try ebay or octopart.com or findchips.com

[@ieast007]

Jameco claims to have them. www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?refineValue=EXAR+Corporation&refineType=String&langId=-1&productId=34972&catalogId=10001&sub_attr_name=Manufacturer&storeId=10001&krypto=zF68DEtssBD5VI%2BVlv9RkZh%2BVo6y2pPGE86qDzbwZau20vajWZQm%2BC%2FalG5uGVDV1kLn6ef%2Fg4YnA6C%2FqO%2F77A%3D%3D&ddkey=https%3AStoreCatalogDrillDownView

[@paulantony5086]

well explained with real test thanks

[@atomictraveller]

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.

[@KainkaLabs]

Did you operate your kit with (slightly less than) 12V? Remember that the fake XR2206-chips are 100% compatible except for that they only work up to 12V supply voltage.

[@atomictraveller]

@@KainkaLabs homemade variable voltage PSU, swept to ~18V. the chip with the kit that gives me a pulse has no date marking, the "other" ones i bought are dated 0919 but give a flat signal where the other gives pulse. some of the reviews for these kits on amazon are about the same, chip absolutely worthless.

[@KainkaLabs]

Hm. Strange. I still think that it´s wrong wiring or wrong supply voltage. Did you only supply GND and +12V and not +/-12V? We sold hundreds of these kits (with my special annotations) and haven´t had a single complaint.

[@atomictraveller]

@@KainkaLabs the kit/PCB i have is for DC :/

[@californiakayaker]

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.

[@KainkaLabs]

You need an extra-circuit for the sweep-input of the chip. That doens´t fit any more onto the PCB. Today you can get relatively cheap function-generators with a sweep-function. Or you google "XR2206 sweep generator" or similar to find examples of the necessary extra circuit.

[@johnhodgson4216]

Thank You for giving the fixes

[@pilotox]

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!

[@believeornot12]

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.

[@KainkaLabs]

Not that I know of

[@ohmedarick1]

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

[@t1d100]

Some folks in the comments state that they bought original XR2206 chips from Jameco. Although they list the manufacturer as XR, the picture of the chip is clearly a Chinese clone, IMHO. As of 06/08/2022.

[@peatmoss4415]

Besides ICs, there are all kinds of electrical components that are "counterfake".

[@johncoops6897]

For *DOWNLOAD LINK* : Roger made an error (it's not a "https" site), so the CORRECT LINK IS: www.kainkalabs.com/upload/index.php?f=15f605449521b3 For *MORE SOLUTIONS + Frequency Control LINEAR* : I just found some great articles on fixing even more XR-2206 issues. Find the PDF of Elektor magazine December 1984 on WorldRadioHistory website - there are 2 articles starting on pages 24 and 30 respectively. Great information, can improve the performance even more (but not easily inbuilt into the chinese kit).

[@iotrix]

As of July '23 this is perhaps the most valuable comment. Re link you are correct; for less savvy use very old browser to proceed. 2. I did not find the " Elektor magazine December 1984 on WorldRadioHistory website" Could you provide link. I did however find these articles in Elektror Electronics India, issue Jan 1985. It could be just the reprint. The only inconvenience this is not OCR treated pdf. ia600804.us.archive.org/20/items/ElektorMagazine/Elektor%5Bnonlinear.ir%5D%201985-01.pdf

[@johncoops6897]

@@iotrix - Sorry, I didn't get notified of your comment! I have *LOTS MORE INFO below* ... It seems that Elektor UK requested that all issues were removed from WorldRadioHistory website. The Elektor India Jan 1985 you linked is an exact reprint - the pages 1.20 to 1.22 are probably better info than project pages 1.26 to 1.31 One problem is that the Elektor circuit is more complicated because it uses Split +/-15V supply and runs the XR2206 from +/-8V, so generates a -5V to provide the total 3V voltage swing for the VCO. However, note how it derives its offset voltage from the Internal Vref (Pin 10) and then keep reading to right at the end... ... Today I found an even cleverer solution in 2 other mags *"Radio Electronics May 1988"* and *"Elektor India Jan 1978"* which are much better suited for the eBay kit. They uses a simple resistive voltage divider between (their regulated) +12V and Ground, with one or 2 Pots to vary the voltage from 0V to 3V as required by Pin 7. Basically, it is just pretending to be a "Frequency Sweep" input. ... The 2 designs are slightly different, and I think the Elektor Jan 1978 might be better for this application. However because this eBay kit is portable the VCC may be unstable, I am thinking maybe use a small LDO Reg to generate a stable (say) 3.3V from the VCC, then divide that down for the Frequency Pot controls. ... Finally a thought... Theoretically the XR2206's internal reference voltage 3V is available at Pin 10, so it might well be as simple as connecting the Frequency Pot(s) straight off that (providing it doesn't load it too much). I will mock it up to test, and found some old original XR2206 chips, so I can test with the clone chip first 😏

[@egemen_isk]

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

[@KainkaLabs]

No.

[@jlucasound]

@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. (?) :-)

[@sw6188]

The XR-2206 will be a fake. These chinese kits always use fake ICs. Exar Corporation was bought out a few years ago and the new owners discontinued various old products including the 2206, and Exar haven't made them for a long time.

[@dnbstreamer]

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?

[@KainkaLabs]

What? The XR2206 does not a charge-pump or something like that to generate higher voltages than the supply voltage. So you must be doing something wrong when you measure 16V with 12V input supply-voltage.

[@dnbstreamer]

i probably shorted something together when i soldered it in school lol. Becaue I have 12v coming in but 16v after the connector.... so confusing@@KainkaLabs

[@nidusa1]

having a hard time finding a 1 mega ohm Potentiometer to replace the middle Fine Knob (R7) per suggestion on Kainkalabs schematic. the ones I find do not have 3 pins going down - they go to side. does anyone have a model number I could google. thanks

[@filtermindmusic4208]

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

[@KainkaLabs]

No. The problem comes from the voltage as soon as it gets higher than 12V.

[@MatzeMaulwurf]

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 :)

[@KainkaLabs]

The voltage divider R3/R5 has to be as low impedance so that the load through the amplitude potentiometer does not appreciably change the virtual ground voltage at the midpoint of R3 and R5.

[@markderlo212]

So if the board as such (not the chip) is the exact copy of the original Exar cct then why all of these changes must be made ?

[@KainkaLabs]

Who says, that their circuit is an exact copy of the EXAR application-example circuit in the datasheet??? It´s of course not.

[@roliveira2225]

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?

[@KainkaLabs]

Link has been changed to the kit in our online-shop where you can also find the documentation. Should work now. Built-manual is only in German until now.

[@roliveira2225]

​@@KainkaLabs Thanks!

[@williamjohnlittle816]

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

[@georgekruger4297]

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?

[@KainkaLabs]

If you use the electrolytic (10...100µF) at the output to get an AC-coupled signal and only probe it with the 1 or 10 Megohm input impedance of your oscilloscope, the initial DC-offset discharges only very slowly with a time-constant of R*C which is hundreds or thousands of seconds! Put a 10k resistor to ground behind the electrolytic and the DC-offset will be gone more or less immediately :-)

[@georgekruger4297]

Thankyou, yes, i clearly didn't listen closely enough to your video :)

[@mikeychris1989]

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.

[@KainkaLabs]

I only recently discovered by chance that there also 8038-based kits available. I haven´t checked one yet but perhaps will buy one or two and try them out. Will be interesting to see if the Chinese also fake the ICL8038

[@rusty1187]

I have built several 8038 circuits, and they are fairly limited on frequency range. But for an audio generator, it works quite well!

[@joaocarvalho1424]

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.

[@Igor_user]

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

[@jasonbrambach6957]

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

[@sw6188]

All the XR-2206 chips in these china kits will be fakes. Exar Corporation was bought out a few years ago by MaxLinear and they ceased production of a number of Exar's popular products including the 2206. As it was, Exar hadn't made them for some time. A friend recently gave me a function generator from the 1980s and it has an original XR-2206 in it with a date code of 8430 (30th week of 1984). It has the genuine XR logo on it and these china fakes look nothing like it.

[@SidneyCritic]

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.

[@KainkaLabs]

You don´t have to limit the voltage. All digital logic IC´s (exept the very first CMOS-series) can safely deal with overvoltages. They have input protection diodes going to ground and Vcc which deflect overvoltages (or negative voltages) to Vcc and GND. The only thing you have to limit is the current through these protection diodes. Let´s presume the datasheet of your logic-series says that the max. current into any input is +/-10mA. If you have a 10V signal into a 3.3V logic-input, then the minimum value of the input resistor (or pull-up of the XR2206) is: R(min) = (10V - 3.3V)/10mA = 670 Ohms That means that even a 1k resistor would be sufficient and a 10k resistor would be absolutely safe. The other possibility would be to use a voltage divider. A 10k/10k or 1k/1k-Divider would make a 5V square-wave output at the center-tap of the divider from a 10V square-wave input.

[@jasonbrambach6957]

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!

[@KainkaLabs]

Remember that the display of the numeric values can be switched on and off: "Press [ SEL] so that t imebase is highlighted. Hold down [OK] button for about 2 seconds. This will turn on/off measurement readouts." Firmware for the DSO138 can be found on the Jyetech homepage: www.jyetech.com/Products/LcdScope/Firmwares_138.php How to upgrade the firmware: www.jyetech.com/Support/HowToUpgradefirmwareByBootloader.pdf Perhaps I will create a patreon account for donations. I hate the monetarization-function of KZbin videos. 1.000 views give you 1$ if you monetarize a channel. That´s not worth the annoyance for the viewers concerning my very-special-interest channel with ca. 1.000 subscribers.

[@user001sg9]

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?

[@KainkaLabs]

There is no reason why it´s not possible to get below 10 Hz. If you are using an output capacitor to get an AC-coupled signal, the value has to be quite large (>100µF)

[@rusty1187]

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.

[@KainkaLabs]

Unfortunately not

[@murugesanr1691]

thank you very much sir..

[@browaruspierogus2182]

Yeah I bought two XR DIY and neither worked....

[@user001sg9]

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.

[@manusoftar]

The link is kinda "brokenISH" at least my antivirus (ESET Internet Security) is blocking it due to an issue with the ssl certificate, like it is not trustable or something or it is revoked...

[@KainkaLabs]

Link is corrected. Try it here: 1drv.ms/u/s!AmW9-q-1GZM1ip5wO7uvHpcenfI14g?e=m4TqeJ

[@KainkaLabs]

Link has been changed to the kit in our online-shop where you can also find the documentation. Should work now. Built-manual is only in German until now.

[@falmircamion3534]

At18' 45" : Shark waves... Taaaada taaaaada tadatadatadatada... ;-)

[@jlucasound]

JAWS!! :-)

[@uwezimmermann5427]

just to defend the "engineer", the 5.1kohm of the divider are actually taken from the datasheet...

[@KainkaLabs]

Right. But this shows that the Chinese either don´t fully read or understand the datasheet and how to achieve a better control of the output amplitude.

[@ozzymandius666]

@@KainkaLabs All your schematic downloads are gone?

[@johncoops6897]

@@ozzymandius666 - Nope, schematics are in zip file link in description. Note Roger made an error in the download link. He wrote www.kainkalabs.com/upload/index.php?f=15f605449521b3 but it's not https, so the CORRECT LINK IS: www.kainkalabs.com/upload/index.php?f=15f605449521b3

[@robertturner4913]

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.

[@KainkaLabs]

In fact EXAR is still in existence but they don´t produce their old analog ICs anymore for a very long time now. en.wikipedia.org/wiki/Exar_Corporation The frewuency determining cpacitors are in fact all ceramic ones (MLCC). They are of course microphonic and would never be used here in a precision circuit. But this purpose here to have a small, cheap, potentially battery-operated general-purpose function generator, it´s OK :-)

[@arthurboulton4511]

Very informative thank you, great tutorial

[@cmarston8342]

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

[@solidhit2]

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?

[@KainkaLabs]

With a linear pot you don´t have to rewire the connections because a linear pot is symmetrical (while a log-pot is not symmetrical concernings it´s outer connections) The only thing that remains a bit annoying is the counter-intuitive rotation.

[@Igor_user]

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

[@KainkaLabs]

It´s an open collector output. So you can with a pullup-resistor get basically any output voltage.

[@VahidBehravanVahid-Behravan]

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

[@KainkaLabs]

Could you explain your question a bit more clearly. I just don´t get it.

[@WestCoastDP]

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

[@KainkaLabs]

What do you mean by "variable" square-wave? Variable amplitude?

[@WestCoastDP]

@@KainkaLabs I should have said - variable amplitude. The fix Square-wave is too strong for testing my audio amp.

[@Igor_user]

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 ?

[@KainkaLabs]

One cannot say if XR2206 or ICL8038 The MAX038 was superior to all others chips before. I have made also a video about a Chinese MAX038-kit. Today DDS-chips are way better than any of the above mentioned.

[@jlucasound]

Hi Roger!!

[@jasonbrambach6957]

"pub" below was meant to be "pcb" ...but auto correct screwed it up!!!

[@jlucasound]

That's funny! "From the image of the Pub in your videos..". :-) Where are we? England, I guess. I'm going out for a Pint. Maybe a Yard. :-) Cheers, Jason!