Vintage Heathkit IG-1271 Function generator troubleshoot and repair - Page 1
Forum section: electronics / repair

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 16, 2015, 11:36:02 pm
content: While sitting at home today sick (Bad head and chest cold) I decided to try my luck at repairing a function generator I recently picked up for 5 bucks. I quickly knew the fault was a shorted component and decided to use a 1.5 volt battery as a load to trace down the faulty component. I was able to repair the unit and now need to do an alignment on it and give it a good cleaning.And no I am no ways a master video blogger, just an old country boy trying to learn more things.I hope some enjoy it.Link to site pictures:http://gokarters.com/smf/index.php?topic=2486.0

author: Vgkid
author_rank: Super Contributor
timestamp: September 17, 2015, 02:18:42 am
content: Thank for the video, I can tell you are from the south.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: September 17, 2015, 02:34:00 am
content: Good troubleshooting skills and thanks for taking the time and posting the video. The best techs and engineers are the ones that make do with what they have available. Done it with even multi million dollar Avionics systems, to just hobbyist projects, or repairs.Would replace all the tantalum capacitors, unlike other types of capacitors, the tantalum capacitor failure mode is usually short circuit they do sometimes catch fire.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 17, 2015, 09:33:11 am
content: Quote from: Vgkid on September 17, 2015, 02:18:42 amThank you.Guess my southern talk gives it away

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 17, 2015, 09:49:15 am
content: Quote from: OldSchoolTechCorner on September 17, 2015, 02:34:00 amIt seems that tantalums die hard when they go, and like to take other parts out. If the circuit does not need a tight tolerance I replace with electrolytic. More frequency sensitive areas I will use modern tantalums.When doing a repair like this video I want to do it with the simplest tools I have. Even though I may have the newest fancy gadget.Thanks very much for your comment.Hoping my videos will improve over time.

author: Muttley Snickers
author_rank: Unknown
timestamp: September 17, 2015, 01:05:23 pm
content: Thanks Radio Tech for a great video and a fantastic job of resurrecting some equipment that otherwise may have been discarded and lost for good, coincidentally I happened to spend most of this morning working on an old Heathkit VTVM - IM 11 valve analogue meter which was given to me and thought that I would spend some time getting to know it a bit better.It uses a single phono jack for the probe input and I intended to drill out the front panel and install a couple of 4mm banana jacks but after consideration and a coffee I decided to leave it original and make up a dedicated lead set instead, for me it's more of a novelty than a meter that I would use.Thanks for the schematic on the whiteboard tip, I have a big magnetic whiteboard which is never used and tend to have notes scribbled on bits of paper and they either get shredded or put away somewhere in the archives to be found again 10 years after they are needed.Best regards and many thanks from even further down south.Muttley

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 17, 2015, 03:12:59 pm
content: Quote from: Muttley Snickers on September 17, 2015, 01:05:23 pmThanks Muttley,It was fun working on it and saving it from the dead.I had a IM-11 before and wish I still did. These are great meters for working on vintage tube gear. There is a string of 22 meg resistors in the "AC balance" line, pay close attention to those.Mine had been switched out to BNC and worked pretty good. I now have 2 B$K 177 meters and a no branded one.If you get a chance post up some pics. I plan on doing a few more videos in this series.Thanks againBTW,I got that idea about the white board from Dave. And since it was magnetic it doubles as a schematic holderI also have a 38 inch monitor beside my work bench..

author: Muttley Snickers
author_rank: Unknown
timestamp: September 18, 2015, 01:33:34 am
content: As requested, cleaned and calibrated at no extra charge, enjoy....

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 18, 2015, 01:39:49 am
content: Oh my! Vintage porn!!!That meter is beautiful Muttley. And the face looks great. Did you polish it?Very clean, I like it. Notice you still have the paper coated capacitor in it. Or is that a new cap hiding under and old skirt? I work on vintage stuff a lot and folks like to keep it as vintage as possible. I remove the old cap from inside the paper and stuff a new one in it.Thanks for posting that, was a pleasure to look at.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: September 18, 2015, 04:02:00 am
content: Quote from: Muttley Snickers on September 18, 2015, 01:33:34 amHave a VTVM and works great still with still the original parts, when I bought it just had a loose wire, but in like new condition, with box. Now see your motivated me to clean the contacts and may replace selenium rectifier with diode and resistor and maybe capacitor. It not bad, test fine and meter does work fine.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 18, 2015, 09:23:16 pm
content: That's a nice Knight you have there. I have never owned a knight VTVM. I do have a knight tube tester. I appreciate you guys posting these old meters. Guess I am a tube fanboy. I love old stuff.Hope Dave don't read this, may think I am a grey beard......Naw, he too busy doing real stuff

author: Joule Thief
author_rank: Regular Contributor
timestamp: September 18, 2015, 10:45:44 pm
content: Buddy.I enjoyed watching your troubleshooting video.I love the vintage repair vid's.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 19, 2015, 12:45:52 am
content: Quote from: Joule Thief on September 18, 2015, 10:45:44 pmThanks. I am pleased that you enjoyed it.I am planning on doing more soon. I have lots of tube and vintage solid state stuff here that needs repair. Some radios and some test gear.

author: Muttley Snickers
author_rank: Unknown
timestamp: September 19, 2015, 12:54:14 am
content: I suspect that the Knight is a cheap knockoff of my Heathkit, you can tell by the later battery and the bodgy wiring....From a time when bodge wiring and components were the accepted method and anything too pretty stood out like a sore thumb, I still use these methods....Muttley

author: AMR Labs
author_rank: Frequent Contributor
timestamp: September 25, 2018, 05:44:02 pm
content: Quote from: Radio Tech on September 16, 2015, 11:36:02 pmHey Radio Tech,I am aware this is an old thread, but I know you are still active on Youtube, so I'm hoping you are also still checking this forum. I was wondering if after the repair you managed to properly calibrate your IG-1271 as described in the manual, mostly in terms of the output frequency dial linearity properly aligning at the 0.1, 1.0 and 10 dial marks.Got actually an SG-1271 off ebay, so this was factory wired, not a kit. No problems with this unit, so just wanted to do the cal procedure to make sure everything is on spec. First one is instructed to do the lo/hi dial calibration, which is basically to adjust both the Low Freq Dial adjust and Symmetry adjustment trimmers to get an even 100Hz triangle wave output at 0.1 dial position, CHECK. Then rotate dial to 10 position and calibrate High Freq Dial adjust trimmer for a 10KHz output, CHECK. And finally set dial back to 1.0 position (where before any further adjustment I'm now reading 833Hz output at this point) and readjust Low Freq Dial adjust trimmer for 1KHz, CHECK. Everything dandy so far, but now when I go to check the frequency output at the 0.1 dial position I do get 225Hz, instead of the expected 100Hz. At this point I am still getting 1KHz at the 1.0 position, and 10K at the 10 position, but apparently there is no way to get 100Hz at the 0.1 dial position without disturbing the calibration of the 1.0 position. I've done the calibration steps several times over as indicated in the manual, but always arrive at the same result: 225Hz at the 0.1 dial position, while 1.0 and 10 are still correct. And if I set the 0.1 dial position to be back to 100Hz, the 1.0 position will read 833Hz instead of 1KHz. The 10 position on the dial will still be accurate at 10KHz output.So given that Heathkit has not always exactly been known for accuracy, I wonder if this error on the 0.1 dial position was considered a "normal", or if there might be an actual still undiscovered problem in this unit, or maybe an error in the calibration procedure? I've also checked voltages around the main variable oscillator circuit and everything agrees to what is shown in the diagram. Even checked resistance and tracking of the R103 dial pot which is 1K LIN, and it seems ok as well. Function-wise everything else seems to be working fine in the generator, besides the 0.1 dial position error.So what gives? Before I start what might turn out to be a wild goose chase, anyone have any ideas or suggestions, or maybe ran into the same calibration problem? Anyone out there with an IG-1271, could you please check your output frequency at the 0.1, 1.0 and 10 dial positions (use the 1K range) and report back findings?UPDATE: replaced all 10uF 35V Tantalum caps (seven in total) because I saw some switching noise on both +15 and -15 buss supplies. I did not help much. Switching spikes exactly correspond to highest and lowest part of sine and triangle waveforms, and rising and falling on square wave. So I guess that noise is part of the design as well.