Calibrating temps on my FX-888d with a thermocouple - Page 1
Forum section: electronics / beginners

author: cdev
author_rank: Super Contributor
timestamp: December 16, 2020, 04:05:49 am
content: My FX-888d got accidentally decalibrated and now I have to reset the temperature, has anybody done this?I have two themocouples, one is a stainless steel one in a probe (seems perhaps too large and bulky to work well for this) and the other is just the thermocouple, both were quite inexpensive.. Has anybody made a habit of doing it? The user interface on the FX-888D is to say the least, not very usable.Excuse me for what must sound like a dumb question, but I am wondering what the best way to make thermal contact with the thermocouple is, I guess just try it.Perhaps mount one on a piece of wood sandwiched between two small pieces of copper? Or should I just buy a dedicated soldering temp thermometer on Banggood or similar? Maybe I will do that.My FX-888D has suddenly become unable to reach adequate temps, it can barely melt solder, so it must have gotten decalibrated..I hate having to keep their truly terribly written instruction sheet around. Something as simple as a soldering iron should not require that.

author: edpalmer42
author_rank: Super Contributor
timestamp: December 16, 2020, 05:05:02 pm
content: Can you disassemble that iron? I have a cheap soldering station. When the iron started having trouble getting hot enough, I pulled it apart and found that the heater wires had partially unsoldered themselves from the small board inside the iron. A quick cleanup and resoldering and the iron was operating properly again.

author: Electro Fan
author_rank: Super Contributor
timestamp: December 16, 2020, 10:02:14 pm
content: I have a Hakko FX-888D and went through the same process. I wish I could tell you it was easy and definitive but for me it wasn't. I tried with a Fluke 179 thermocouple and some other DMM/thermocouples, an IR thermometer and the Hakko RST FG-100.The whole process was similar to comparing DMMs and other test equipment. You might need two or three pieces of equipment to triangulate to the likely correct measurement.First I tried to rely on the Fluke 179 thermocouple. As your questions indicate, it's hard to get the tip and the thermocouple to mate together in a way that results in repeatable and confidence-inspiring measurements. I think the problem/challenge is a bit like soldering in general, you need to get good thermal transfer - but until you know what technique makes this possible and unless/until you have a way to verify the measurement (maybe with a second piece of test equipment), you are pretty much just guessing/hoping.For a while I relied on what the Fluke thermocouple indicated and adjusted the Hakko (and also a Weller WESD51) accordingly - but I wasn't happy with the soldering results. I also tried a Fluke IR thermometer but that didn't inspire much confidence.Finally I ordered what I thought is a real Hakko RST FG-100 soldering thermometer. I also ordered what I thought and still think are real Hakko sensors for the FG-100 - and I also ordered two extra/different sets of clone sensors.The FG-100 with the Hakko sensors inspired more confidence than any of the previous approaches. The more confidence I gained with the FG-100 the more I worked on my technique with using the Fluke thermocouple and after a fair amount of trial and error I started to see how better thermocouple technique (ie, holding the thermocouple appropriately/firmly to the soldering iron tip with good surface contact) could produce results reasonably consistent with the Hakko FG-100 and Hakko sensors.(fwiw, along the way I also did my best to compare the Hakko sensors to the clone sensors and the clone sensors seemed to produce results that were highly consistent with the Hakko sensors - but maybe that's because they are all clone sensors...?)Here is a youtube that shows a guy trying to ascertain what is a real Hakko FG-100 and what is a clone and what the differences might be. After watching this I think my Hakko FG-100 is a clone - which is unfortunate but it's possible, I think, that the clones might produce reasonably accurate results. I think the nature of this type of thermometer and the sensors is such that it's an easier way, and I think possibly a more accurate way, to measure soldering tip temperatures than with a thermocouple that is typically packaged with most DMMs.My sense is that if you can find either an affordable real FG-100 or a clone that you believe performs consistent with the real FG-100 that it's a pretty handy device.In my case, once I got to a somewhat confident ability to know what was approximately 1 F (or 1 C within maybe +1/-1 C) then I went back and used the user interfaces on the Hakko and the Weller to re-calibrate them. Neither had been particularly close to right until this point in the process. With each iron better calibrated I did some more tests to confirm that the two irons were now reasonably agreeing with one another and with the Hakko FG-100 using all three different sets of sensors, and with the Fluke 179. Since then I have begun to rely much more on the readouts from the Hakko and the Weller but I'd give most of the credit for breaking through to temperature confidence to the FG-100. (Other people's mileage may vary.)I hear you on the UI on the 888 not being super great but once you have it calibrated changing the temperature as you need to for each soldering job is actually pretty easy and fast (you just toggle to each of the three digits and up or down within a digit - whole process might take about 2 seconds once you get it). I have found that having a baseline preferred temperature depending on what you normally use (lead or lead free solder) and what you normally solder (through hole or SMD) and the size of the pads, etc. is pretty valuable, but then as you move from your normal/baseline setup to something new, you can benefit further by adjusting the temperature as needed for new set ups, and it's therefore good to be familiar with the Hakko's interface so you can quickly raise or lower the temperature accordingly.Once I got this far I began trying more diligently to learn to solder SMD. I got some practice boards and SMD components, and also a microscope. With the microscope I could see much more clearly how the flux was flowing, how the solder was flowing, how the joints looked, etc. With pretty good (very good) visibility I then moved on to ordering various tips for the Hakko and experimented with tips sizes and shapes which is what taught me that each situation can benefit from a tip that is appropriate for the size of the component and especially the PCB pad, and that to really dial-in the best looking joints the temperature should be adjusted for the specific setup to yield the best results (and therefore it's important to be familiar enough with the iron's temp UI to make the changes quickly). From there I spent a couple nights just trying a wide range of temperatures for various tips and component and pad sizes until I had a sense of how long (1 second vs 2 seconds, etc) I wanted to hold a particular tip to a particular size component on a particular size pad and how to in general improve the soldering technique. It was very helpful to have a baseline readout on the 888D so that when I went through the various trial and error temperature ranges I had a sense of confidence in the temperature readout.HOWEVER, having said ALL THAT, while it's very interesting and most comforting to know (or think you know) what in real terms is the actual temperature being used, the larger moral to the story is that for non-commercial purposes it probably doesn't matter exactly what the temperature really is and what does matter is that you apply the appropriate temperature for the job (tip, component, pad, type of solder) being undertaken. So even if you don't know what the exact temperature is, once you have a baseline you can probably get there with relative settings.LAST HOWEVER:In the end, considering everything above, my personal strong first choice is to first establish as much confidence as possible/practical in the soldering iron's temperature readout, and then be able to use that as a dependable reference as you adjust the iron for the specific job at hand.Hope something in here might help you dial-in your setup.

author: wraper
author_rank: Unknown
timestamp: December 16, 2020, 10:08:17 pm
content: Quote from: Electro Fan on December 16, 2020, 10:02:14 pmTechnique is simple. Put a junction of thin unsheathed thermocouple into a solder blob on the tip. When using specialized soldering iron calibrators you do exactly that, they just make operation easier since thermocouple is supported by third lead.QuoteIt's weird you even thought it could possibly work.

author: cdev
author_rank: Super Contributor
timestamp: December 16, 2020, 11:05:51 pm
content: Thanks to both of you!Okay, now I am in a better mood. I was thinking about using a very small piece of copper as a thermal conductor and making a circular holder for the thermocouple at its edge that ensured the thermocouple would get as hot as the square. But thinking about it, the thermocouple which looks delicate- even so-since its rated to be usable at some very high temperatures,mustbe able to maintain its physical integrity under those high temperatures.I was just worried about solder somehow bridging the two conductors and shorting it out.This Hakko thermometer sure is overpriced for what it appears to be. How can they get away with charging over $200 for it? What the hell is it made out of/why so expensive?Also, is a thermocouple-supporting-DMM just a very sensitive voltmeter like they appear to be or is there some additional magic involved?Hakko really should make a small card that they include with their pretty soldering iron so thick-headed people like me can attach it to the thing ruining its snazz but making the labyrinthe menuless interface somewhat more difficult to screw up. I am going to try to make one, if I feel its worth sharing I'll turn it into a small printable PDF and upload it. Its a miracle I managed to get away with not screwing it up for so long.Thank God microcontrollers are so much cheaper now so they can actually have user interfaces that tell you things. Ever since I lost the cal Ive been using my old 936 clone which just has the pre-d 888's digital readout and knob, and I really prefer that. The calibration is just SOOO far off now, its basically useless until its fixed.

author: wraper
author_rank: Unknown
timestamp: December 16, 2020, 11:12:42 pm
content: Quote from: cdev on December 16, 2020, 11:05:51 pmIt will have barely any effect on measured temperature. Thermocouple is just two wires from dissimilar alloys connected together. And thermal EMF voltage is formed over the temperature gradient in wires, not in the joint.

author: jerryk
author_rank: Regular Contributor
timestamp: December 17, 2020, 04:34:46 am
content: Did you try a factory reset?I had the same problem and the reset solved it.Jerry

author: Electro Fan
author_rank: Super Contributor
timestamp: December 17, 2020, 07:49:18 am
content: Funny thing, this thread got me re-looking temps and various related soldering stuff tonight. In the process my 888D went into lala land. I did a reset and it came back to normal life.Separate off topic question: is a 15 degree C lower ambient temperature (in the winter) likely to show up in a lower iron temp for a given set temp (generally used in the summer)? If so, how much? Just a degree or two, or something closer to the 15 C change in the ambient temp?

author: amyk
author_rank: Super Contributor
timestamp: December 18, 2020, 10:00:30 pm
content: Quote from: cdev on December 16, 2020, 11:05:51 pmThey are charging for the name. What they actually cost to make is probably around the same as the clones.Look up "Hakko FA-400" for some even more crazy overpricing. It's literally just a fan in a box with a filter...QuoteA thermocouple has a nonlinear voltage-temperature response, so there is some compensation required. But all of that can be built into a single chip, and explains why the clones are just as accurate. There is nothing particularly tricky about it.

author: cdev
author_rank: Super Contributor
timestamp: December 19, 2020, 02:08:14 am
content: I just tried it, will update this thread in a bit and let you know if its worked..Thank you.My God, Hakko are such idiots for not putting this info in the manual.Quote from: jerryk on December 17, 2020, 04:34:46 am

author: cdev
author_rank: Super Contributor
timestamp: December 19, 2020, 11:26:18 pm
content: @JerryK THANK YOU!its now fixed, as far as I can tell, at least good enough for me now!This should be in a sticky for all Hakko-FX-888D owners.Their documentation is horrible.

author: jerryk
author_rank: Regular Contributor
timestamp: December 20, 2020, 08:00:57 am
content: Glad it helped. I stumbled across the video at least a couple or more years ago and was glad to see it was still around to share. I'm going to write that reset procedure down while it's fresh in my mind.Jerry

author: cdev
author_rank: Super Contributor
timestamp: December 21, 2020, 11:18:05 pm
content: The use of the U makes me also wonder if it switches between US? (Fahenheit "U") and the rest of the world (represented as Asia? Centigrade "A"?)) and sets the respective defaults.(Update, it does!)

author: Electro Fan
author_rank: Super Contributor
timestamp: December 23, 2020, 05:51:54 am
content: Quote from: jerryk on December 20, 2020, 08:00:57 amhttps://kb.hakkousa.com/Knowledgebase/10599/How-do-I-reset-the-HAKKO-FX888D-back-to-factory-default-settings