Building & Enclosing an XR-2206 Based Function Generator Kit - Page 1
Forum section: electronics / beginners

author: Barry A. Waters
author_rank: Contributor
timestamp: October 28, 2022, 10:39:51 pm
content: Having more FUN with this stuff than the law allows! About 20 years ago (if memory serves) I bought a Jameco JE2206 Function Generator Kit not realizing I needed equipment I did not have to actually calibrate and make use of it so into the closet it went. My meager arsenal at the time included a neat Radio Shack 22-181 Multimeter / Component Tester, a few breadboards, a DC power supply, a raft of components and a stack of Forrest M. Mims III books, all from Radio Shack. I STILL had a TON of fun back in the day but every now and then I'd wonder about that kit and if it would ever get built.Fast Forward to 2022 when my equipment inventory saw the addition of a Rigol DS1054Z Oscilloscope and a Rigol DG822 AWG. With the DG822 more or less eliminating the need for the JE2206 Kit I STILL felt it should see the light of day so I dug through the closet and out it came to see if I could make something useful out of it. Thanks to the kit being a SPLENDID product in its own right, and with help from an exceptionally informative video by Collin Cunningham on enclosing it once finished, it has FINALLY been assembled w/enclosure and I couldn't be happier. Apparently, all good things come to kits that wait!In short, the PCB part of the build process was a BLAST and testing it in all of its 'nakedness' went smoothly. Doing the enclosure work was a bit more 'fiddly' (I had never done something like this before AND I deviated somewhat from Collins example video) BUT once I decided on an internal connection and user interface design it came along rather nicely.Aside from laying out the control panel somewhat differently than Collin did in his video, the biggest alteration concerned the internal PCB connections for the various external components the kit requires. Switches, Pots, Output Points, Input Points, Power Connection (I built the 12V DC Supply version of the kit instead of the 6V+/- Split DC Supply version) and, of course, a Power On indicator LED to top things off.All of these things need to be there (more or less) AND I wanted to allow for easy replacement of anything that might go bad, to include the XR-2206 IC which I installed via a socket. As I mentioned above, the BIG (and most time consuming) change was to install individual Male Header Pins where each external component attached to the PCB which was followed by adding Molex Female Connectors to every external component's associated wires.All of that may SOUND good at first (especially from a maintenance standpoint) BUT added connections (especially if they are of poor initial quality or end up degrading over time) can introduce any number of odd problems but I seem to have escaped those issues for now and am pleased with the results. All external components can now be simply 'unplugged' from the PCB should a failure or service require it. It also simplifies testing if something goes wrong. I LOVE those aspects of the 'plug-in' concept as long as all of those extra connections don't come back to bite me. To be a bit more precise, I changed the original 22 solder connections into 66 by going the pin/socket route. Yes Sir, I'm GREAT at stuff like that... :-)The kit itself is indeed a wonderful thing. I've read that some have had issues with it but I had none. With its spiffy new cabinet (home-made AND home-did!) I think the Rigol DG822 is jealous. It produces a couple of nice Variable Frequency Fixed Amplitude Square Waves (Full Swing and Half Swing), and a Switch Selectable Sine or Triangle Wave whose Frequency and Amplitude can BOTH be adjusted within 4 Selectable x100 Band Widths that top out at 100kHz.I'll say that I can highly recommend this project for someone (like myself) who's getting ramped up in the hobby and has access to an O-Scope, especially if you've never enclosed your work before. It produces a very usable piece of test equipment and, as Collin alluded to in his video, there's nothing sweeter than looking at that magical box and being able to say "I built that!" :-)The only things left hanging now are deciding on how to go about physically labeling the controls (the terminology shown in the 'example' photo are, of course, subject to change) AND figuring out how to add and make use of the SWEEP and AMPLITUDE Inputs. The purpose and implementation of those two features continue to escape me and I'm in dire need of an explanation of their 'whys and hows'.The Jameco instructions for the kit indeed discuss both the SWEEP and AMPLITUDE Inputs but my lack of expertise is preventing those instructions from ringing true for me. I currently 'THINK' I understand the SWEEP Input as a thing that repeatedly increases (or decreases?) the Frequency Output between a Start - Middle - End setting with the AMPLITUDE Input doing something similar for the Amplitude setting. Hopefully I'm not too far 'off target' there. Any insights on those two Inputs would be much appreciated! :-)Barry(Photos Split into two Posts...)

author: Barry A. Waters
author_rank: Contributor
timestamp: October 28, 2022, 10:42:33 pm
content: Additional Photos Attached. What a FUN project! :-)Barry

author: ledtester
author_rank: Super Contributor
timestamp: October 28, 2022, 11:52:12 pm
content: Coincidently, I just picked this up from a retired medical device researcher a couple months ago:

author: ledtester
author_rank: Super Contributor
timestamp: October 29, 2022, 12:09:49 am
content: QuoteThe output frequency can be modified by applying a voltage at pin 7 or 8. For a sweep you would need a separate ramp signal and apply it to one of those pins. The particulars can be found in this datasheet, Figure 10 on page 8 and the section "Frequency Seep and Modulation" on page 11.https://www.sparkfun.com/datasheets/Kits/XR2206_104_020808.pdfThere's a good youtube series on building a function generator around the XR2206:Signal Generator Projects - Scullcom Hobby Electronicshttps://www.youtube.com/playlist?list=PLUMG8JNssPPwjMZ0eUjj5Zahx2yjz6Alo

author: Barry A. Waters
author_rank: Contributor
timestamp: October 29, 2022, 12:36:56 am
content: Quote from: ledtester on October 28, 2022, 11:52:12 pmDamn - That looks to be the same vintage as mine (Rev B)! I think the current Jameco offering is up to Rev E now. You can rest assured that Rev B WORKS! :-)Barry

author: MikeK
author_rank: Super Contributor
timestamp: October 29, 2022, 02:31:44 am
content: Unfortunately the real XR2206 is NLA...only clones now.

author: coromonadalix
author_rank: Super Contributor
timestamp: October 29, 2022, 02:47:51 am
content: The Max038 was a very good replacement for a project and could go higher, not sure it still exist ?? i have 2 of them somewhere loll

author: MikeK
author_rank: Super Contributor
timestamp: October 29, 2022, 12:50:47 pm
content: Based on the MAX038-based func gens available on AliX and Amzn that chip is being cloned/faked too.

author: magnetchief
author_rank: Contributor
timestamp: October 31, 2022, 02:41:45 pm
content: Hello Barry my old friend !Small world.

author: Barry A. Waters
author_rank: Contributor
timestamp: November 06, 2022, 02:15:30 pm
content: Quote from: magnetchief on October 31, 2022, 02:41:45 pmSteve! I thought you and your Magnets were near, my watch stopped!Small world indeed!

author: radiolistener
author_rank: Super Contributor
timestamp: November 06, 2022, 05:30:55 pm
content: can you show it's output on oscilloscope? Does it have glitches?

author: jonpaul
author_rank: Super Contributor
timestamp: November 06, 2022, 07:37:53 pm
content: My 1973 Popular Electronics Super Sweeperhttps://worldradiohistory.com/Archive-Poptronics/70s/1973/Poptronics-1973-10.pdfIntersil 8038 FG ICenjoyJon

author: Kleinstein
author_rank: Super Contributor
timestamp: November 06, 2022, 09:29:13 pm
content: The max038 was available for only a rather short time. At the time the performance was quite good and would still be nice chip for some used. Kind of a beefed up (much faster) version of the ICL8038.The classic XR2206 and 8038 are also no longer made. Today digital control and DDS has replaced those chips in many cases.There are supposed to be some xr2206 clones from China. AFAIK these kind of work, but have limitations with the upper supply limit. So with an old circuit / kit they may need a lower supply.In theory one could build such a genrator by hand from separate parts, a bit like some older HP generators did. The AM modulation part could still be a bit tricky.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 07, 2022, 11:01:42 pm
content: well i found them loll4x Max 0382x XR22062x XR8038brand new, got then years ago .... never used, must be worth millions lolleven some rare MC1466L regulator ic's

author: Barry A. Waters
author_rank: Contributor
timestamp: November 08, 2022, 10:39:13 pm
content: Quote from: radiolistener on November 06, 2022, 05:30:55 pmAssuming this question was directed at me, yes, I can post a few images (probably tomorrow) and no, using the original kit chip (built with the 12V Single Supply Option), I'm not seeing any glitches other than only a wee HINT of an over-run / under-run spike on the peaks of the Sine waves. I believe these are due to the 'reshaping' the chip does from Triangle to Sine output as the Triangle peaks are sharp. In general the wave outputs look very clean to me as do the Full and Half Swing Square Pulse Outputs.I recently sourced a couple of replacement XR-2206CP ICs from Jameco to compare.The original from the old kit is marked 9322 and both replacements are marked F0918. I swapped in one of the replacements today and aside from needing a slight calibration to adjust clipping and symmetry (three internal trimmers on the PCB which I will do tomorrow) I see no noticeable difference. It looks to behave pretty much the same as the original kit's chip.Barry

author: Barry A. Waters
author_rank: Contributor
timestamp: November 11, 2022, 12:28:03 am
content: Here are some Sine and Triangle wave images from the scope. These were with my second recently sourced (Jameco) XR-2206CP F0918 IC installed and calibrated. Everything looks pretty clean to me (see my prior post) and I don't see much difference between the three ICs but then I'm new at this. What you see (in order) are a Sine and Triangle wave at Mid-Frequency for each of the kit's four Bands: 1) 1Hz - 100Hz, 2) 10Hz - 1kHz, 3) 100Hz - 10kHz and 4) 1kHz - 100kHz.I really took my time (and busted my balls!) on solder connection quality and kept an eye on my wire-lead lengths and routing. Perhaps that paid off in some regard?Barry

author: radiolistener
author_rank: Super Contributor
timestamp: November 11, 2022, 01:19:12 am
content: It seems that I see some glitch on the top part of the waveform (see two last screenshot).Can you show this part of waveform with better time resolution?

author: Barry A. Waters
author_rank: Contributor
timestamp: November 11, 2022, 01:26:18 am
content: Quote from: jonpaul on November 06, 2022, 07:37:53 pmWow - That thing looks TOO Cool! Way before my time. In 1973 I thought a 'resistor' was someone that got roughed up by the Police at a protest... ;-)Barry

author: rdl
author_rank: Super Contributor
timestamp: November 11, 2022, 02:16:23 pm
content: From what I've read, that little blip at the top of the waveform with the XR2206 is pretty much normal.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 11, 2022, 05:14:44 pm
content: That spike at the top of the sine is common with Xr2206 based generators. AFAIK it is not directly a fault of the chip, but the pinout of the chip makes it very easy to make a poor layout and get capacitive coupling from the square to the sine. AFAIR this should be from pin 11 to 13 and 14. With a careful layout one keep it quite small.For normal use that extra blip is not such a big problem and can sometimes even be helpful as a marker to see phase shift even with a single channel - like not a bug but a feature.

author: Bud
author_rank: Super Contributor
timestamp: November 11, 2022, 05:25:13 pm
content: I too bought a XR2206 ftom Jameco 20 years ago, but just the IC. Based on the date code it was a clone, not the original chip.

author: MrAl
author_rank: Super Contributor
timestamp: November 11, 2022, 05:46:35 pm
content: This brings back memories.Back around 1978 i think it was i built my own function generator using the 8038 i think it was made by Intersil at the time but dont remember that well.It wasnt too bad for what i needed it for. I wanted to be able to fine tune the frequency so i put a big 4 inch diameter knob on the pot. I made the knob myself i couldnt find one that big, although there may be available a 'wheel' to some toy that can be fitted onto the pot shaft.I ran it off of a 9v battery, and one day when i was connecting the battery to do some testing someone interrupted me an i accidentally connected the battery backwards for just a split second. Needless to say, that was the end of the chip. I never fixed it for some reason. I did get a new chip though sometime around 1994 maybe but i never got around to using it.The thing is though function generators have come down a lot in price over the last 20 years so you can get a pretty good one now that goes up to 10Mhz or even 40Mhz depending on what you want to do with it. If i needed that high i would get one. Unfortunately there was another chip very similar to the XR2206 or whatever that part number was, and it went up to 10Mhz. It was basically the same thing but went up to a higher frequency. That was discontinued though.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 11, 2022, 06:02:29 pm
content: The faster Chip was the max038. It had impressive specs for the time, but was relatively expensive when new, and than quickly disappeard. AFAIR Maxim relied on a relatively special process to get those parts manufactured and the company that provided it rather suddently terminated that process / plant.Modern day DDS based generators have largely replaced the old style triangle VCO based ones.For simple analog control the old style chip still has it's benefits. DDS based generator also have some principle limitations with the triangle waveform. So it makes sense that the Chinese make a replacement - just be a aware of some limititations with the supply. AFAIK the maximum supply voltage is a bit lower than for the original.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 11, 2022, 06:53:23 pm
content: The 3 knowns chips where XR2206, ICL8038, and the MAX038At time Maxim MAX038 where given freely as samples ... surely did not help selling themI saw a few going up to 25$ a piece few years later, and now on Fleabay we see some prices examples lolll

author: themadhippy
author_rank: Super Contributor
timestamp: November 11, 2022, 07:06:07 pm
content: QuoteHeres one i made earlier, at least 30 years ago,and still in regular use.

author: MK14
author_rank: Super Contributor
timestamp: November 11, 2022, 07:55:43 pm
content: Quote from: jonpaul on November 06, 2022, 07:37:53 pmI misunderstood your post. When you said 'My', I thought you meant that you had built (as an electronics hobbyist), one of those frequency sweep generators.I didn't realize you were part of the team of three, who designed, built and wrote the article for it, in the first place!Almost 50 years ago, wow!

author: rdl
author_rank: Super Contributor
timestamp: November 11, 2022, 11:49:13 pm
content: The XR2206 was discontinued in 2011, though the last production run could have been years before that. 20 years ago cloning/counterfeiting was not as prevalent, so there's a good chance the one you bought was real.Quote from: Bud on November 11, 2022, 05:25:13 pm

author: Barry A. Waters
author_rank: Contributor
timestamp: November 12, 2022, 03:42:25 pm
content: Quote from: rdl on November 11, 2022, 11:49:13 pmI have five of these ICs now, 1 from the 20 year old Jameco Kit, 1 from the current Jameco kit, 2 from Jameco recently ordered a la carte and one in a recently purchased Elenco FG-500K kit. I guess I need to do a shootout?I've seen a video on YouTube where it states (and shows) that running some 'clones' at 12V and above causes them to become unstable. I'm at 12V now and have not noticed any stability issues. As soon as I get a 2.1mm Male DC Power Connector so I can rig up a cable and connect a variable DC supply to my Magic Box, I can test this on all 5 ICs. Are there any other 'clone issues' folks have found that I could include in my poking around? Maybe build a second box using a Split Supply instead of a Single and see if that matters?Barry

author: MrAl
author_rank: Super Contributor
timestamp: November 12, 2022, 05:27:46 pm
content: Quote from: Kleinstein on November 11, 2022, 06:02:29 pmOh that's interesting i never looked into the reason for discontinuing the chip. I wanted to build one with that chip at one time and could not find a supplier. I guess there are some sold on the web now for a high cost. Not sure if i need it anymore.Yes the DDS type took over i think. I have a small board i think it was $8 (USD) and it goes up to 40MHz sine and square, dont think it does triangle though. The frequency increments are based on a 32 bit programming word so the increments are very tiny providing for a large range of frequencies.

author: MrAl
author_rank: Super Contributor
timestamp: November 12, 2022, 05:29:26 pm
content: Quote from: coromonadalix on November 11, 2022, 06:53:23 pmYes i think i saw prices like that some 10 years ago, but that was long after i wanted to build one. At that time i couldnt find any for sale anywhere.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 12, 2022, 06:24:29 pm
content: I remember the 038 because I thought about building one. However it first was hard to get one and later nearly impossible, so that stopped it.DDS can do sine wave very good and with a comparator one can get a good rectangle as well. A few DDS chips offer triangle too, but with limited performance (e.g. more jitter, limited frequency) - the triangle and even more saw tooth shapre is tricky as a DDS, as the ideal of phase interpoaltion not longer works.

author: Bud
author_rank: Super Contributor
timestamp: November 12, 2022, 06:53:01 pm
content: A few years ago at a local hamfest I pulled from a seller's junk bin a couple aluminum boxes that seemed to be part of vintage avionic or military equipment, with "Modulator" written on them. I bought them to use as RF enclosures for my projects. When I got home and opened them up, each of them had a board with genuine XR2206 inside.

author: Barry A. Waters
author_rank: Contributor
timestamp: November 12, 2022, 11:56:08 pm
content: Quote from: radiolistener on November 11, 2022, 01:19:12 amYour eyes do not deceive you and they appear on BOTH the Sine and Triangle waves on the kit's highest Band setting (1kHz - 100kHz) and, apparently, all throughout that Band's Frequency Range for this particular IC (1 of 5 I have and, with this one being recently purchased, a likely candidate for being a 'Clone'). I don't see them on the lower three Band Settings.I'm trying to compile a 'Clone Issue' list for the XR-2206CP ICs and will add this to it. Instability at 12V and above is the only other issue I've found that folks have actually experienced with the so-called 'Clones'. Pointers to other's reported issues (specific and not general 'it's wonky' complaints) would be much appreciated. Maybe there are a few common / repeatable issues that could easily be checked to see if you have a 'Good' one OR a 'Bad' one. That's my thinking anyway...Barry

author: ledtester
author_rank: Super Contributor
timestamp: November 13, 2022, 01:04:53 am
content: Guess I should build my kit to see if it has the glitch...

author: MrAl
author_rank: Super Contributor
timestamp: November 13, 2022, 06:01:08 pm
content: Quote from: Barry A. Waters on November 12, 2022, 11:56:08 pmThat's usually caused by a quick change to the input of an op amp. The op amp can not respond fast enough to make the output impedance near zero as the input pulse makes it's way around the op amp. It also happens in roll your own triangle generators. Only (partial) fix i think is to lightly filter the output.

author: Barry A. Waters
author_rank: Contributor
timestamp: November 14, 2022, 04:38:49 pm
content: Quote from: ledtester on November 13, 2022, 01:04:53 amBy all means! :-)Barry