At 30:18 on the video...Check the two resistors R107 and R104, as well as C31 and C2 electrolytic capacitors. The two resistors appear to have gotten hot and moved on the pads and the C31 and C2 caps look bulged. You can check the capacitance on them with some multimeters but an ESR meter is the best way to check them. However, if there's any question I'd probably replace all the electrolytics on the board with good quality replacements from Digikey or Mouser. For sure the ones that are near that controller and appear to be bulged on the top.
Nothing boring about your videos Ivan! I think the purpose of your videos are for me to learn something because that's what happens each time I watch one. Great troubleshooting technique. Note on your question of DIP vs SOIC designation on the chips; DIP is the old style dual inline package with feed thru pins while the SOIC is the small outline IC about half the size with the surface mount pins. I'm sure you ordered the correct ones. Looking forward for the followup video.
Hi Ivan... You did a very good diagnostic... If you look at the four transistors within the chip's schematic you will see two transistors tied to VDB and two transistors tied to ground... There are two different "grounds" one looks like an arrow the other looks like a "brush"... one is chassis ground (arrow) and the other is a floating ground... I was an electronic tech that my jobs went away (consumer electronics then industrial (audio/video) electronics... I'm retired and do mostly car repairs for family and friends... You are spot on on diagnosis... BTW the BT on the part is for standard through the board designs and the SOIC is for a smaller version that is for surface mount... clip off old leads and remove the IC then remove each lead from the board and clean out the mounting holes... This will keep you from damaging the board and traces... I'm a regular for pine hollow and SMA...Dave
What a great video. I'm amazed how you follow logic tracing. When I ran my Cadillac service business, I had to do the same only with vacuum lines and many mechanical relays. Electronics was way beyond my ability. You sir have great reasoning and logic.
Thank you for the comment, Stephen! Electronics is a fascinating subject. I am often surprised just how far some common sense and a few simple tools can get you in a diagnosis... I would rather deal with wires than vacuum lines haha
I'm sure I'll never repair a Genie Boom Lift or a Kappa Lens Edger, but I still find the troubleshooting approach to both cases interesting. Awesome videos Ivan! Looking forward to Part 2.
Your problem is now going to be removing the old part on that multi-layer PCB. If you have experience with this type of soldering, great. If not, get help, because it's easy to trash the board. Hint: cut the pins off the dead chip, as close to the body as possible, and heat and remove one pin at a time. Then clear out the holes with a solder-sucker, or with desoldering braid, before soldering the new part in. Soldering iron should be grounded, and it should be handled on a conductive mat, with a wrist strap properly grounded to prevent static damage to the components. Also, another poster caught some possible heat damage, and/or a failing capacitor. Check that out before you power the board to avoid damaging the new part. Just beware that surface-mount soldering by hand requires some skill and technique. Again, if possible, get help from an experienced tech. Great logic finding the fault! Good luck.
Totally. Cut it all the way, heat the solder pad and pick the rest of the legs with small tweezerrs for SMD. Then suck the rest of the solder. But, BORST CASE, just cut and solder over the pads. Not the best job, but you are not risking the PCB. This IC uses heat dissipation on the middle pins. This will hurt heat transfer. But, it uses heatsink. If Im with a 40K machine and PCB is putting fight, I would do this way. EDIT: On power pads, like VLOAD, GND and OUT .. could be big planes of copper so sucking the solder could be a pain. You need more power (on the iron) for those and low power for the small ones that are signals. If using a soldering stick, well, power I mean, you need to wait MORE prior sucking due to heat transfer. I had a goot with a push button to get 90W over the sandard 25W. Pefect for this jobs.
According too the spec sheet, That chip is only designed to handle 1.5 amps output. I'm guessing it controls some other component which handles the higher current. I think you should at least check the possibility. I'm loving the video. It's the thrill of the chase. Your willingness to tackle oddball projects will take you places. Thanks for bringing us along!
Good troubleshooting! I would trace the power supply lines to that chip, and make sure that the shorted chip didn't take out series current limiting resistors or something similar. There was a large SMD resistor near the shorted chip that was crooked on the pads, possibly as a result of getting hot enough to melt the solder. There was also an electrolytic cap nearby that looked like it was beginning to swell a bit. Replacing both of these along with the chip would be cheap insurance against future failure. Make sure that you use a proper thermally conductive epoxy to attach the heatsink to the replacement chip, and clean off all the old epoxy off the heatsink before regluing.
Possibly due to excessive heat dissipation, resulting in enough heat to melt the solder. I would recommend checking the resistor values at the very least, or just replacing them outright. The small electrolytic cap near the chip should be checked/replaced, as well.
Great video Ivan. This video brings back a lot of memories. I used to do exactly this style of repair on all kind of weird and wonderful electro-mechanical systems from large industrial printers, CNC machines etc. with usually limited repair info. Your diagnosis was pretty damn good - my only real comment would be that you should invest in an ESD strap and mat before opening up the shielding on that board and handling it. Some of these boards can be super sensitive to accidental ESD. Also... it's probably too late but you should take that board to someone with a proper surface mount repair station. They will be able to look over the board for you with a practiced eye - as others have mentioned some of these resistors and caps look a bit suss. A good tech might give that board another 20 years of life, rather than it failing again in 12 months. It's a lot lot messier cleaning up after an exploded cap than fixing it before hand. It might cost you a couple of hundred $ but could save the customer the machine. I'd be hesitant to do that repair with just a soldering iron - i'd really want a vacuum desoldering gun at least
I have some experience with similar stepper driver chips. Some notes: Looks like your board implements pretty close the "Typical Application" in the datasheet. The resistor marked "R500" is the 0.5 ohm current sense resistor -- the A3955 uses the voltage across that to sense the current. The bad resistor placement suggests that both of these got overheated, and you should resolder them into proper position, if not replace. (You may want to look into typical inexpensive temperature controlled soldering irons, Solder Wick, and even low-end hot-air stations for this kind of work.) The big caps also look iffy. You may wonder how a 30V supply, into the 2.4 ohms of the winding, could possibly limit the current to 1.5A that this chip is rated at: The chip uses feedback from the current sense resistor to control PWM (at the microsec timescale 8:15 ) which switches the voltage supplied to the motor. The instantaneous current is limited by the inductance of the motor (ie: not the resistance per se). Using a seemingly high voltage supply with a low resistance winding allows the chip, for a brief time (say 100's of microsecs) at the beginning of a new step, to apply a continuous "overvoltage", to "overcome" the slowing effect of winding inductance, ultimately allowing a much higher stepping rate. Precise algorithm details are in all the "decay" discussion in the datasheet. (As a separate feature, the PWM also allows microstepping.) Finally, as others have said, do not connect/disconnect the motor while the system is powered up (or not quite powered down), and don't temporarily connect with clip leads that can connect intermittently. The energy stored in the winding magnetic field, upon disconnection, can produce a high voltage pulse and fry the drivers. That's a very popular and predictable failure mode :-). Good luck with the replacement -- high chance of success!
Very interesting video Ivan. Can´t wait to see part 2. As all told you check those resistors and capacitors. I think you should look in to getting your self a good microscope and so on for working on electronic boards.
I wasn't sure you knew it or not, but at 27:56, you were pointing at the very thing that tells you that it is a 6 layer board. Basically each layer has a number and when you back-light through the PCB, their shadows appear within their respective boxes... usually...
28:08 (top left of PCB) seems to confirm that it is 6 layers. As far as I can tell in the video. But it is good to "carefully" check - sometimes newer revisions will delete some of the inner layers. So for example you might only have layers 1, 2, 5 and 6, or some variation thereof...
HA! I can totally picture that. Ivan's luck though he'll be on his way to Fukishima, with a Russian friend to help film, and he'll have to chase down a shorted wire on the plane on the tarmac. Good video.
This is a cool one Ivan. Interesting stuff. Speaking of eBay, I bet you could find an entire used machine for 5k! Or at least some spare Essilor parts. Thanks and looking forward to the nail biter repair!
I had to do similar back-tracing in my 1995 Nissan ECM. The ohmmeter sure came in handy. The problem was that the Check Engine light no longer illuminated. I found that the Hitachi HF9921 chip failed internally and was completely open-circuited (infinite resistance). I discovered that these chips were discontinued as well, but I was able to order replacements from UT Source in China on Amazon.com. They were used chips harvested from other ECMs. I got a de-soldering iron and replaced the chip and was able to successfully restore the Check Engine light function. The ECM can even flash codes via the Check Engine light. Don't give up hope and I'm sure you'll make a successful repair!
Ivan - the 4 digits on the second line of the part is the date code. YYWW 2004 Week 32 etc. The bottom line could be the Lot Trace Code - it will contain info about where the part was packaged, where the die was made etc. You can often find out this information in the vendor data sheet under MFG Part Number or ordering information. Also when probing from the bottom side of the board pin 1 will have a square pad. You found the problem no matter what pin you labeled them initially - Great job.
Hey man great video, is there anyway to speed up the cut times on this edger? I'd like to run a job in 1 to 2 mins. Just cutting plane polarized slates. Any help would be great!
Very nice! It's great to see people tear into stuff like I do and figure out how to fix it. Maybe I missed it in the video but what was the resistance of the windings on the old motor on the bad side when isolated from the board? You measured with the motor still connected to the main board so your resistance measurement would have been skewed by the shorted microcontroller. My question, essentially, is what took out the motor controller? Was the motor shorted and damaged the controller or maybe something is/was jammed mechanically and prevented the motor from moving when powered?
The driver chip is internally protected from overcurrent caused by stalled motors and the like. The chip itself likely failed from repeated thermal cycling over years of service. Such failures are common with power semiconductors, especially items like this which were likely borderline for their application, requiring a glued on heatsink to keep temperatures acceptable.
Yes, that's true. I just wondered if the original motor windings were actually shorted or not. If not, then I'd agree with your assessment and I'd probably replace both chips while I had it apart.
Original motor actually measured to spec when disconnected. However, since they already purchased a new motor, I installed it as insurance. After all, the windings in the old motor may short out when it gets hot...
I'd be suspect of some bad electrolytic caps then. I mentioned in another comment that C31 and C2 look like they were bulging. Usually, though, when electrolytics go bad they increase in equivalent series resistance (ESR), so hard to tell what caused it. Probably just worn out like Bob says.
Question is why did those motor drivers fail? They obviously got really hot and caused the SMD resistors to flow and move on the board as many other have pointed out. Is there a limit switch, encoder or something that has gone bad causing the motors to drive into stall current? Definitely replace those electrolytic caps They are now cooked being so close to that heat sink.
Ivan, I strongly suggest that you check the MOSFET Transistors as they are the devices that have sufficient current capablities to drive the motor windings (12A). I guess base this on experience of similiar circuits. It likely that one (or more) of the power transistor blew and took out of the driver chip. The root cause of the problem was either the shorted motor winding or the MOSFET transistor shorting because that is where the real current is.
Hi I am having thesame problem but mine is worse because my machine won't diagnose and it shows same error code during diagnosing any help please? It all stated with the door giving an error code when closing
The middle numbers are the date code. If you were not able to find the chip, you could replace the chip with a more modern device, you would just to have to do some spec matching. Get as close as you can, and may have to put in a little transition board to convert the pin out to the new device.
Bit late to the party but the very first page of the A3955 datasheet lists the superceded part, A4975 which is available on Digikey. At a glance it looks to be functionally identical with the same pinout. The difference is the 4975 is based on mosfet technology whereas the 3955 is a darlington pair.
to remove bad chip: first cut all the legs off from the black body of the chip, then simply desolder each pin separately. also check surrounding components, caps might be on their last legs to.
Interesting! 20 years in an industrial setting before it broke .... certainly wasn't manufactured by GM! :D My proudest electronic moment was successfully repairing a 400w power inverter. Back when I was at MMI in Phoenix ('99-'01), I was playing around in my apartment with a 1960s battery charger hooked to the inverter. I tried the TV, a blender, and an electric can opener. All worked, except for the blender on high speed. In the middle of playing with the different speeds on the blender, I heard a POP! Smoke and stink poured from the unit! I took the cover off and it looked just like a firecracker had gone off inside ... then I saw the empty metal shell of a capacitor! What in the world happened? Got out my brand new Blue Point multimeter (that I also still use), and tested the charger output. Well come to find out, my old battery charger put 20v into this thing, LOL! No wonder! Capacitor popped in protest. :D Went to Fry's Electronics right down the road, bought the same capacitor for under .50 cents, soldered it in, and I'm STILL using the same unit today! I keep it in my truck for road trips. :)
hah, I dove into electrical and electronics repair as a kid and repaired tons of everything by age 18, not just electronics all sorts of construction/remodeling (trade school for industrial electricity too) in my two years there, I repaired lots of "training equipment" and other electronics that the stupendous previous year/s classes burnt up. the computer/electronics teacher came in and asked why I was there, not in his class and if I wanted to switch courses, I replied this is a softer ride :))
Just a thought how about installing a 16 pin socket and putting the new chip into the socket it would be much easier to replace if it every went bad again.
I would normally suggest exactly that, but on this IC, the center ground pins are fused together for increased thermal dissipation, and should (if the PCB layout person did it right) be connected to a large area of copper foil to help carry away heat. Adding a socket between the chip and the PCB may make it harder for the heat to get dissipated into the PCB.
Hi... thanks for your video... , I have problem with our delta essilor edger, that is " error A121" (communication error from module to edger) , any advice ? Thank in advance..🙏🙏
Hot air rework stations like that are good for SMD rework, but for thru hole boards, you really want a vacuum desoldering tool. About the cheapest option here would be one of the Chinese units sold under a bunch of different names and model numbers. Here is a typical one: www.memotronics.com/vacuum-desoldering-rework-station-digital-temperature-controlled-dual-lcd-new/
Since the chip is dead you can just cut through the legs with small cutters. Then the legs can individually be removed from the board. Easy to do with even with a basic soldering iron, for pcb use ideally it needs to be temperature controlled. Can even do the same with some smd chips using a scalpel.
love it ! exercise in common sense and logic. sadly this unit is probably seen too many stress cycles. for some reason electronics are that way . when ya get it fixed it should still be on the short list for replacement. it will break again but when? continuity tests can bite you in the ass if you dont be sure to isolate to double check. some meters if there is a diode in circuit it wont show unless you reverse the leads.
You’ll want to get a good thermal glue to replace what the heat sync was held on with. Thermal paste won’t hold it for very long with the vibration the machine produces.
always do circuit check around the chip before installing the new one. Some times, other things can trigger a failure. When it comes to POWER devices, conterfeits are a problem. They dont perform to spec of blow too easy. Try to seek for an original part if possible to avoid failures. I made some repairs in audio and anything that handles power like transistors and power amplifiers can give trouble, because they appear to work, and work for a while and then you have issues again. There are some site devoted to obsolete parts that sell original ones.
The chips on eBay from China, etc. are likely the real deal - I don't think it's common for anyone to rip off chips unless they're particularly common or valuable. You probably don't want those anyway though because those eBay sellers in China usually ship by surface mail and you could be waiting a month for the thing to show up. As someone mentioned the 4-digit number elsewhere on the chip is usually a date code with year and week of manufacture.
When I worked at a PCB manufacturer we made 14 layer boards that were about 8 mm thick. About 20 inches square. Each one (empty) weighed about 8 to 10 pounds. I think they went into mainframe computers.
In worse case you could replicate the functions with discrete parts (phase logic + MOSFET drivers, etc but dialing in the decay will be a bitch. Make sure to order spare chips in case you missed a bad connection or power feed issue. A loose motor connection can kill a MOSFET instantly (either discrete or part of a chip) no matter the supposed protections. Never disconnect motor leads while the driver is powered. Typically there are snubber diodes between the driver and motor leads, they get fried then take out the mosfet junctions. These doides have to be very/ultra high speed types or they will lag behind the pulse speed and short out. They almost always fail shorted rather than open. Each of those chips drive 1/2 of the motor so plan on replacing in pairs just in case.
Get a temperature controlled soldering iron (about 35W should be fine, more is better) and a vacuum solder sucker. Set the iron temperature to 700F. Get a real Edsyn SOLDAPULLT DS-017 - avoid the chineesium junk. ADD FRESH solder to each joint when you initially heat it. Leave the iron there for 20 to 30 seconds, then immediately remove the iron and suck the solder with the soldapullt. Wiggle the pin with a screwdriver after to make sure it's actually free. If you yank out the plated through hole because the pins aren't completely free, it's going to be bad news (or you'll have to run bodge wires on top of the board to fix it). Should be no sweat to remove a through hole dip chip, even on a 6 layer board (you can see the layer markings on the bottom left edge of the board at 27:57). Without a vacuum solder sucker, it's a giant PIA. If there's one pin you can't clear the hole on using the vacuum tool (most likely the ground pins, and because your iron is too low wattage), leave it until the end. Once all the other pins are free, heat that pin with the iron while you pull the chip out. To clear that hole once the chip is out, soldering iron on one side of the board, solder sucker on the other at the same time.
Heh, just a few yeah... hobbies include designing and building circuit boards, as well as fixing most anything I come across (including BGA rework). Day job is working on the insides of the chips, specifically the most important one in your laptop (well, the ones that will be in your laptop in 2018 or 2019 and beyond :-) ) I have much more advanced soldering equipment now, but I started with a hand-me-down 35W weller iron probably 19 years ago, and added a soldapullt a few years after that - you can do a LOT with those basic tools. If you ever get in over your head, or want to attempt some some internal ECM / PCM repairs, I'm always a USPS flat rate box away!
hope someone comes on here and tell us how to decipher both the part number lines. Are they just part numbers or do they also give info on functionality?
Most of the numbers are batch code and date of manufacturing they are used by the factory for quality assurance purposes..it would be nice if they underlined the actual chip number's but then again that may be asking too much..at least they didn't etch the number's off like the Chinese factories are doing lately to stop anyone else copying there work even tho they steal a lot of there's in the 1st place lol....Very Well Done to Ivan for going to Component level Top Man 👍👍👍👍
A4975 is a successing part of A3955 of Allegro Micro Systems. I guess we can get A4975 easier and we can find equivalent part from other semiconductor manufacturer.
Be careful with the ugga duggas. Check the caps. Those are electrolytic and they tend to go explode when they get old. That's usually what fails on a board if the magic smoke didn't leave it.
the other numbers wouldn't matter to much they use those for date code and batch id for most integrated circuits edit dip is the through hole dual inline package and soic is a surface mount version small outline integrated circuit
If I would have known it was this complicated I would have said $5K easy. I hate cutting bourgeoisie capitalists a break. I'm so ashamed I told you to charge them a lower price. I'll never forgive myself.
You definitely should get into an industrial electronics repair business (preferably obsolete equipment as there you're customers will be entirely at your mercy) as you'd make a hell of a lot more money fixing business critical machines that you will fixing rusted out cars for broke people. There are a lot of machines like this. For example a CNC lathe, a CNC Waterjet or plasma cutting table. There is a whole world of industrial equipment that is computer controlled that HAVE TO WORK or people don't get paid. You're smart enough to realize this fact yourself. Time to start thinking about your future Ivan. 2000 era Fords and Dodges aren't where it's at. You're young enough to make this change now. Your wife works and you have no kids to feed. Time to get out of the muck and onto the paved highway. This ain't Russia Ivan here you have complete free will. Use it.
you make a very valid point, I have been told the same thing and still find myself working on old junk cars for little pay. I've spent so much money in schooling and tools, not to mention all the time to learn this trade that its hard to walk away. Companies that rely on one person or one machine should have realized this in the beginning and started saving for a backup or looking for a replacement.
While I agree that businesses should set aside money for upgrading equipment, since they do take depreciation on that equipment over the years, calling them bourgeoisie capitalists just because they asked someone they know to see if they could fix their machine (when the manufacturer clearly couldn't,) seems a little unfair. Sounds to me like they were willing to pay for the repair and when they struck out with the manufacturer, asked Ivan to see what he could do. Ivan should charge what the market will pay but to just charge extra for no reason, in my opinion, starts to border on an ethical dilemma (at least to me.) His wife works there. As long as they pay for his professional time, I don't see a problem and wouldn't consider them bourgeoisie capitalists. I would be flattered if someone asked me to see what I could do with it. I'm guessing the outcome has already come to pass, but, I'd recommend getting a nice little desoldering machine and adjustable temp soldering iron, and work that into the bill as parts needed to fix it. It's so easy to damage the fine traces on these boards. I'd at least want a nice adjustable temp soldering iron, for sure. Don't go gorilla on the soldering iron. The chip is no good but you have to be real careful with the board or the whole project can be ruined. You'd be amazed at the difference between a cheap Radio Shack soldering iron and a nice adjustable temp soldering iron with soldering quality and board damage.
Johnaclark1: Have you bought and more importantly PAID for a pair of eyeglasses lately? BOURGEOISIE CAPITALISTS. I don't hate them I'm just trying to help Ivan become one.
ivan there are companies that specialize in overstock,obsolete chips relays etc. many meddling ears ago i worked for a company that had customers that specified that type of stuff. A real pita to work with at best. Unfortunately Im out of that business for a long time now and one of the companies we used is out of business. the other business was in Rochester NY , I cant remembee their name but their. aligan was. : We are the leaders on the trailing edge of technology
Hi dear friend,we are un Venezuela en have the same machíne,we hace some trouble cause did not Star to cut,is possible that You can help us,have some mail to contact You,really really thanks
DIP = Dual Inline Package it has legs that go through the board to be soldered SOIC = Small Outline Integrated Circuit. It is soldered to the surface of the board. Surface mount in other words. You can adapt surface mount components to through hole with adapters, but it's not really recommended. www.digikey.com/en/product-highlight/l/logical-systems/surface-mount-adapter-kits
Flush cut pliers. Link to Amazon: www.amazon.com/TDOK-TD-109-Cutter-Pliers-5-Inch/dp/B06W9NMMNK/ref=sr_1_2?ie=UTF8&qid=1506736713&sr=8-2&keywords=flush+cut+plier
Is there nothing you can't figure out? Well done. America needs about 3 million more of you.
At 30:18 on the video...Check the two resistors R107 and R104, as well as C31 and C2 electrolytic capacitors. The two resistors appear to have gotten hot and moved on the pads and the C31 and C2 caps look bulged. You can check the capacitance on them with some multimeters but an ESR meter is the best way to check them. However, if there's any question I'd probably replace all the electrolytics on the board with good quality replacements from Digikey or Mouser. For sure the ones that are near that controller and appear to be bulged on the top.
Nothing boring about your videos Ivan! I think the purpose of your videos are for me to learn something because that's what happens each time I watch one. Great troubleshooting technique. Note on your question of DIP vs SOIC designation on the chips; DIP is the old style dual inline package with feed thru pins while the SOIC is the small outline IC about half the size with the surface mount pins. I'm sure you ordered the correct ones. Looking forward for the followup video.
Hi Ivan... You did a very good diagnostic... If you look at the four transistors within the chip's schematic you will see two transistors tied to VDB and two transistors tied to ground... There are two different "grounds" one looks like an arrow the other looks like a "brush"... one is chassis ground (arrow) and the other is a floating ground... I was an electronic tech that my jobs went away (consumer electronics then industrial (audio/video) electronics... I'm retired and do mostly car repairs for family and friends... You are spot on on diagnosis... BTW the BT on the part is for standard through the board designs and the SOIC is for a smaller version that is for surface mount... clip off old leads and remove the IC then remove each lead from the board and clean out the mounting holes... This will keep you from damaging the board and traces... I'm a regular for pine hollow and SMA...Dave
What a great video. I'm amazed how you follow logic tracing. When I ran my Cadillac service business, I had to do the same only with vacuum lines and many mechanical relays. Electronics was way beyond my ability. You sir have great reasoning and logic.
Thank you for the comment, Stephen! Electronics is a fascinating subject. I am often surprised just how far some common sense and a few simple tools can get you in a diagnosis... I would rather deal with wires than vacuum lines haha
This is why i watch you channel i now that you continue to component level of repair. great video thank you.
I'm sure I'll never repair a Genie Boom Lift or a Kappa Lens Edger, but I still find the troubleshooting approach to both cases interesting. Awesome videos Ivan! Looking forward to Part 2.
Your problem is now going to be removing the old part on that multi-layer PCB. If you have experience with this type of soldering, great. If not, get help, because it's easy to trash the board. Hint: cut the pins off the dead chip, as close to the body as possible, and heat and remove one pin at a time. Then clear out the holes with a solder-sucker, or with desoldering braid, before soldering the new part in. Soldering iron should be grounded, and it should be handled on a conductive mat, with a wrist strap properly grounded to prevent static damage to the components. Also, another poster caught some possible heat damage, and/or a failing capacitor. Check that out before you power the board to avoid damaging the new part. Just beware that surface-mount soldering by hand requires some skill and technique. Again, if possible, get help from an experienced tech.
Great logic finding the fault!
Good luck.
Great advice, Blackhomie1. :)
Totally. Cut it all the way, heat the solder pad and pick the rest of the legs with small tweezerrs for SMD. Then suck the rest of the solder. But, BORST CASE, just cut and solder over the pads. Not the best job, but you are not risking the PCB. This IC uses heat dissipation on the middle pins. This will hurt heat transfer. But, it uses heatsink. If Im with a 40K machine and PCB is putting fight, I would do this way.
EDIT: On power pads, like VLOAD, GND and OUT .. could be big planes of copper so sucking the solder could be a pain. You need more power (on the iron) for those and low power for the small ones that are signals. If using a soldering stick, well, power I mean, you need to wait MORE prior sucking due to heat transfer. I had a goot with a push button to get 90W over the sandard 25W. Pefect for this jobs.
According too the spec sheet, That chip is only designed to handle 1.5 amps output. I'm guessing it controls some other component which handles the higher current. I think you should at least check the possibility.
I'm loving the video. It's the thrill of the chase. Your willingness to tackle oddball projects will take you places. Thanks for bringing us along!
Good troubleshooting! I would trace the power supply lines to that chip, and make sure that the shorted chip didn't take out series current limiting resistors or something similar. There was a large SMD resistor near the shorted chip that was crooked on the pads, possibly as a result of getting hot enough to melt the solder. There was also an electrolytic cap nearby that looked like it was beginning to swell a bit. Replacing both of these along with the chip would be cheap insurance against future failure.
Make sure that you use a proper thermally conductive epoxy to attach the heatsink to the replacement chip, and clean off all the old epoxy off the heatsink before regluing.
Wow! At around 29:30 it looks like there's some really sloppy surface mount soldering with those R104 and R107 resistors.
But they were symmetrical so I thought it was by design haha
Possibly due to excessive heat dissipation, resulting in enough heat to melt the solder. I would recommend checking the resistor values at the very least, or just replacing them outright. The small electrolytic cap near the chip should be checked/replaced, as well.
Seconded.
Also, those traces look awfull skinny for 12A... unless they're doubled up in the layers.
Fantastic Vid! Watched it read every single comment and reply and can't wait for part 2!
This I very much enjoyed. Looking forward to seeing the next one. Thx for sharing.
Great video Ivan. This video brings back a lot of memories. I used to do exactly this style of repair on all kind of weird and wonderful electro-mechanical systems from large industrial printers, CNC machines etc. with usually limited repair info. Your diagnosis was pretty damn good - my only real comment would be that you should invest in an ESD strap and mat before opening up the shielding on that board and handling it. Some of these boards can be super sensitive to accidental ESD. Also... it's probably too late but you should take that board to someone with a proper surface mount repair station. They will be able to look over the board for you with a practiced eye - as others have mentioned some of these resistors and caps look a bit suss. A good tech might give that board another 20 years of life, rather than it failing again in 12 months. It's a lot lot messier cleaning up after an exploded cap than fixing it before hand. It might cost you a couple of hundred $ but could save the customer the machine. I'd be hesitant to do that repair with just a soldering iron - i'd really want a vacuum desoldering gun at least
I have some experience with similar stepper driver chips. Some notes: Looks like your board implements pretty close the "Typical Application" in the datasheet. The resistor marked "R500" is the 0.5 ohm current sense resistor -- the A3955 uses the voltage across that to sense the current. The bad resistor placement suggests that both of these got overheated, and you should resolder them into proper position, if not replace. (You may want to look into typical inexpensive temperature controlled soldering irons, Solder Wick, and even low-end hot-air stations for this kind of work.) The big caps also look iffy. You may wonder how a 30V supply, into the 2.4 ohms of the winding, could possibly limit the current to 1.5A that this chip is rated at: The chip uses feedback from the current sense resistor to control PWM (at the microsec timescale 8:15 ) which switches the voltage supplied to the motor. The instantaneous current is limited by the inductance of the motor (ie: not the resistance per se). Using a seemingly high voltage supply with a low resistance winding allows the chip, for a brief time (say 100's of microsecs) at the beginning of a new step, to apply a continuous "overvoltage", to "overcome" the slowing effect of winding inductance, ultimately allowing a much higher stepping rate. Precise algorithm details are in all the "decay" discussion in the datasheet. (As a separate feature, the PWM also allows microstepping.) Finally, as others have said, do not connect/disconnect the motor while the system is powered up (or not quite powered down), and don't temporarily connect with clip leads that can connect intermittently. The energy stored in the winding magnetic field, upon disconnection, can produce a high voltage pulse and fry the drivers. That's a very popular and predictable failure mode :-). Good luck with the replacement -- high chance of success!
Very interesting video Ivan. Can´t wait to see part 2. As all told you check those resistors and capacitors. I think you should look in to getting your self a good microscope and so on for working on electronic boards.
Maic Salazar That is one 5 🌟 suggestion and would also allow viewers a great close up shot of all the components !
There is a guy on YT called Louis Rossman. It is amazing what he could fix.
I wasn't sure you knew it or not, but at 27:56, you were pointing at the very thing that tells you that it is a 6 layer board. Basically each layer has a number and when you back-light through the PCB, their shadows appear within their respective boxes... usually...
6 LAYERS?!? Holy crap! I thought it was at most three...
28:08 (top left of PCB) seems to confirm that it is 6 layers. As far as I can tell in the video.
But it is good to "carefully" check - sometimes newer revisions will delete some of the inner layers. So for example you might only have layers 1, 2, 5 and 6, or some variation thereof...
One day I expect you'll be driving up to a nuclear power plant. Without a shirt on. In your sandals.
Anything is possible... lol
HA! I can totally picture that. Ivan's luck though he'll be on his way to Fukishima, with a Russian friend to help film, and he'll have to chase down a shorted wire on the plane on the tarmac. Good video.
Let's hope so!
Ivan has totally got this!
This is a cool one Ivan. Interesting stuff. Speaking of eBay, I bet you could find an entire used machine for 5k! Or at least some spare Essilor parts. Thanks and looking forward to the nail biter repair!
Nice work Ivan ,be sure not to make a spectacle of yourself .
And stay focused.
Good job...you look as a well trained person...
I had to do similar back-tracing in my 1995 Nissan ECM. The ohmmeter sure came in handy. The problem was that the Check Engine light no longer illuminated. I found that the Hitachi HF9921 chip failed internally and was completely open-circuited (infinite resistance). I discovered that these chips were discontinued as well, but I was able to order replacements from UT Source in China on Amazon.com. They were used chips harvested from other ECMs. I got a de-soldering iron and replaced the chip and was able to successfully restore the Check Engine light function. The ECM can even flash codes via the Check Engine light. Don't give up hope and I'm sure you'll make a successful repair!
That's fantastic work Ivan.
I don't know why I'm watching this particular repair but for some reason I'm finding it fascinating. Strange but fun. Who knew.....Hmm
Ivan - the 4 digits on the second line of the part is the date code. YYWW 2004 Week 32 etc. The bottom line could be the Lot Trace Code - it will contain info about where the part was packaged, where the die was made etc. You can often find out this information in the vendor data sheet under MFG Part Number or ordering information. Also when probing from the bottom side of the board pin 1 will have a square pad. You found the problem no matter what pin you labeled them initially - Great job.
What exactly is this third (bottom) line? Can it affect the way the IC works? I can't find any information about it from Allegro Microsystems.
great video. can't wait for part 2!
Definitely do more integrated circuit videos- enjoyed !!
I hope you fix it. nice diagnosis. always using your noodle!
Hello, what is the name of the manual bookstore? Can I learn the name of the repair manual booklet?
Man, that was interesting! Great diagnostics!
Hey man great video, is there anyway to speed up the cut times on this edger? I'd like to run a job in 1 to 2 mins. Just cutting plane polarized slates. Any help would be great!
Forgot to add, GREAT VIDEO, thanks for posting.
hi Ivan, where do i get this schematic/wiring diagram of kappa?
Resistance reading wasn’t quite accurate because the motor was still in circuit with the drivers.
Bingo!
Follow up question: because the motor is still good, it's the driver which is shorted. Pulling out the motherboard removed the short.
Very interessting ! Good one !
You do come in handy Ivan!
Very nice! It's great to see people tear into stuff like I do and figure out how to fix it. Maybe I missed it in the video but what was the resistance of the windings on the old motor on the bad side when isolated from the board? You measured with the motor still connected to the main board so your resistance measurement would have been skewed by the shorted microcontroller. My question, essentially, is what took out the motor controller? Was the motor shorted and damaged the controller or maybe something is/was jammed mechanically and prevented the motor from moving when powered?
The driver chip is internally protected from overcurrent caused by stalled motors and the like. The chip itself likely failed from repeated thermal cycling over years of service. Such failures are common with power semiconductors, especially items like this which were likely borderline for their application, requiring a glued on heatsink to keep temperatures acceptable.
Yes, that's true. I just wondered if the original motor windings were actually shorted or not. If not, then I'd agree with your assessment and I'd probably replace both chips while I had it apart.
Original motor actually measured to spec when disconnected. However, since they already purchased a new motor, I installed it as insurance. After all, the windings in the old motor may short out when it gets hot...
I'd be suspect of some bad electrolytic caps then. I mentioned in another comment that C31 and C2 look like they were bulging. Usually, though, when electrolytics go bad they increase in equivalent series resistance (ESR), so hard to tell what caused it. Probably just worn out like Bob says.
Question is why did those motor drivers fail? They obviously got really hot and caused the SMD resistors to flow and move on the board as many other have pointed out. Is there a limit switch, encoder or something that has gone bad causing the motors to drive into stall current? Definitely replace those electrolytic caps They are now cooked being so close to that heat sink.
Ivan, I strongly suggest that you check the MOSFET Transistors as they are the devices that have sufficient current capablities to drive the motor windings (12A). I guess base this on experience of similiar circuits. It likely that one (or more) of the power transistor blew and took out of the driver chip. The root cause of the problem was either the shorted motor winding or the MOSFET transistor shorting because that is where the real current is.
Отжиг! Молодца! Жду вторую серию!
AH HA A BACKWARDS R THAT PROVES IT'S RUSSIAN. Great job man, It's a pleasure watching you work. Thanks Ivan.
One of those sets of numbers is a date code. 0432 is likely the 32nd week of 2004.
Is there any way you have that usser manual for sale?
what next ivan repairing rockets and satellites lol brilliant video
how can i get this manual in pdf please
Yes, I don't suppose you know how to setup a new scanner?
Great find, your are and amazing tech
Hi I am having thesame problem but mine is worse because my machine won't diagnose and it shows same error code during diagnosing any help please? It all stated with the door giving an error code when closing
I think we'll do more support for Ivan by clicking on UA-cam ads, he'll get paid for that too, it would be a sweet bonus!
The middle numbers are the date code. If you were not able to find the chip, you could replace the chip with a more modern device, you would just to have to do some spec matching. Get as close as you can, and may have to put in a little transition board to convert the pin out to the new device.
Bit late to the party but the very first page of the A3955 datasheet lists the superceded part, A4975 which is available on Digikey. At a glance it looks to be functionally identical with the same pinout. The difference is the 4975 is based on mosfet technology whereas the 3955 is a darlington pair.
Wow bud you get some weird ones lol. Glad to see that your not scared to try anything.
to remove bad chip: first cut all the legs off from the black body of the chip, then simply desolder each pin separately. also check surrounding components, caps might be on their last legs to.
Interesting! 20 years in an industrial setting before it broke .... certainly wasn't manufactured by GM! :D
My proudest electronic moment was successfully repairing a 400w power inverter. Back when I was at MMI in Phoenix ('99-'01), I was playing around in my apartment with a 1960s battery charger hooked to the inverter. I tried the TV, a blender, and an electric can opener. All worked, except for the blender on high speed. In the middle of playing with the different speeds on the blender, I heard a POP! Smoke and stink poured from the unit! I took the cover off and it looked just like a firecracker had gone off inside ... then I saw the empty metal shell of a capacitor! What in the world happened? Got out my brand new Blue Point multimeter (that I also still use), and tested the charger output. Well come to find out, my old battery charger put 20v into this thing, LOL! No wonder! Capacitor popped in protest. :D
Went to Fry's Electronics right down the road, bought the same capacitor for under .50 cents, soldered it in, and I'm STILL using the same unit today! I keep it in my truck for road trips. :)
Wow! Great story!
Thanks! I've been told I should write a book, lol ... I've got lots of stories! :D
hah, I dove into electrical and electronics repair as a kid and repaired tons of everything by age 18, not just electronics all sorts of construction/remodeling (trade school for industrial electricity too) in my two years there, I repaired lots of "training equipment" and other electronics that the stupendous previous year/s classes burnt up.
the computer/electronics teacher came in and asked why I was there, not in his class and if I wanted to switch courses, I replied this is a softer ride :))
Just a thought how about installing a 16 pin socket and putting the new chip into the socket it would be much easier to replace if it every went bad again.
I would normally suggest exactly that, but on this IC, the center ground pins are fused together for increased thermal dissipation, and should (if the PCB layout person did it right) be connected to a large area of copper foil to help carry away heat. Adding a socket between the chip and the PCB may make it harder for the heat to get dissipated into the PCB.
Just don't fall into the machine and make a "Spectacle" of yourself ! ..... :-)
Hi... thanks for your video... , I have problem with our delta essilor edger, that is " error A121" (communication error from module to edger) , any advice ? Thank in advance..🙏🙏
It can be done with and iron, but a $35 858 rework station on e-bay would make it quick and painless even if it's a multilayer board.
Hot air rework stations like that are good for SMD rework, but for thru hole boards, you really want a vacuum desoldering tool. About the cheapest option here would be one of the Chinese units sold under a bunch of different names and model numbers. Here is a typical one:
www.memotronics.com/vacuum-desoldering-rework-station-digital-temperature-controlled-dual-lcd-new/
Since the chip is dead you can just cut through the legs with small cutters. Then the legs can individually be removed from the board. Easy to do with even with a basic soldering iron, for pcb use ideally it needs to be temperature controlled. Can even do the same with some smd chips using a scalpel.
love it ! exercise in common sense and logic. sadly this unit is probably seen too many stress cycles. for some reason electronics are that way . when ya get it fixed it should still be on the short list for replacement. it will break again but when? continuity tests can bite you in the ass if you dont be sure to isolate to double check. some meters if there is a diode in circuit it wont show unless you reverse the leads.
You’ll want to get a good thermal glue to replace what the heat sync was held on with. Thermal paste won’t hold it for very long with the vibration the machine produces.
Ebay is definitely my first place to look for hard to find stuff.
always do circuit check around the chip before installing the new one. Some times, other things can trigger a failure. When it comes to POWER devices, conterfeits are a problem. They dont perform to spec of blow too easy. Try to seek for an original part if possible to avoid failures. I made some repairs in audio and anything that handles power like transistors and power amplifiers can give trouble, because they appear to work, and work for a while and then you have issues again. There are some site devoted to obsolete parts that sell original ones.
Excellent advice. I was able to source an original Allegro chip :)
how about a video series about yourself and how you have gotten to this point of knowledge
I and many others would be very interested in this also. If not a series, at least one video!
The chips on eBay from China, etc. are likely the real deal - I don't think it's common for anyone to rip off chips unless they're particularly common or valuable. You probably don't want those anyway though because those eBay sellers in China usually ship by surface mail and you could be waiting a month for the thing to show up. As someone mentioned the 4-digit number elsewhere on the chip is usually a date code with year and week of manufacture.
When I worked at a PCB manufacturer we made 14 layer boards that were about 8 mm thick. About 20 inches square. Each one (empty) weighed about 8 to 10 pounds. I think they went into mainframe computers.
I'm sure you have already been told but the square pad on the chip is pin 1 and each pin is measured in a circular manner.
In worse case you could replicate the functions with discrete parts (phase logic + MOSFET drivers, etc but dialing in the decay will be a bitch. Make sure to order spare chips in case you missed a bad connection or power feed issue. A loose motor connection can kill a MOSFET instantly (either discrete or part of a chip) no matter the supposed protections. Never disconnect motor leads while the driver is powered. Typically there are snubber diodes between the driver and motor leads, they get fried then take out the mosfet junctions. These doides have to be very/ultra high speed types or they will lag behind the pulse speed and short out. They almost always fail shorted rather than open. Each of those chips drive 1/2 of the motor so plan on replacing in pairs just in case.
Get a temperature controlled soldering iron (about 35W should be fine, more is better) and a vacuum solder sucker. Set the iron temperature to 700F. Get a real Edsyn SOLDAPULLT DS-017 - avoid the chineesium junk. ADD FRESH solder to each joint when you initially heat it. Leave the iron there for 20 to 30 seconds, then immediately remove the iron and suck the solder with the soldapullt. Wiggle the pin with a screwdriver after to make sure it's actually free. If you yank out the plated through hole because the pins aren't completely free, it's going to be bad news (or you'll have to run bodge wires on top of the board to fix it). Should be no sweat to remove a through hole dip chip, even on a 6 layer board (you can see the layer markings on the bottom left edge of the board at 27:57). Without a vacuum solder sucker, it's a giant PIA. If there's one pin you can't clear the hole on using the vacuum tool (most likely the ground pins, and because your iron is too low wattage), leave it until the end. Once all the other pins are free, heat that pin with the iron while you pull the chip out. To clear that hole once the chip is out, soldering iron on one side of the board, solder sucker on the other at the same time.
Thank you for the detailed tips! It sounds like you have soldered more than a few circuitboard components :)
Heh, just a few yeah... hobbies include designing and building circuit boards, as well as fixing most anything I come across (including BGA rework). Day job is working on the insides of the chips, specifically the most important one in your laptop (well, the ones that will be in your laptop in 2018 or 2019 and beyond :-) ) I have much more advanced soldering equipment now, but I started with a hand-me-down 35W weller iron probably 19 years ago, and added a soldapullt a few years after that - you can do a LOT with those basic tools. If you ever get in over your head, or want to attempt some some internal ECM / PCM repairs, I'm always a USPS flat rate box away!
hope someone comes on here and tell us how to decipher both the part number lines. Are they just part numbers or do they also give info on functionality?
I don't know for sure on this particular chip but often the four digit numbers are production date codes, i.e. 0625 would be the 25th week of 2006.
Most of the numbers are batch code and date of manufacturing they are used by the factory for quality assurance purposes..it would be nice if they underlined the actual chip number's but then again that may be asking too much..at least they didn't etch the number's off like the Chinese factories are doing lately to stop anyone else copying there work even tho they steal a lot of there's in the 1st place lol....Very Well Done to Ivan for going to Component level Top Man 👍👍👍👍
wow you are a GOD!
Did somebody know for what is error code A121?
Part 2 please
I would definitely replace that bulged capacitor next to the chip....
Buy two when do find it!
Hello sir I am Moroccan you can give me the technical catalogue of the apparatus essilor kappa please
If the new IC doesn't come with heatsink mounted it might save time to order some heatsink adhesive now
to reattach the old one.
I did think of that...back to eBay!
Frowny face - to steal a phrase - "There's your problem lady."
A4975 is a successing part of A3955 of Allegro Micro Systems. I guess we can get A4975 easier and we can find equivalent part from other semiconductor manufacturer.
You can buy a A4975SB it is a drop-in replacement for the A3955
Wish I knew that sooner...the A3955 is hard to come by!
У тебя нет в электронном виде мануала?
very good ivan, get 2or 3 on order, and lets have some of your good soup.sam you will get it fixed thats for dam sure.
Ivan, if you were in Hawaii the locals would surely be calling you a smott buggah.
Thats why most of the pins on a CPU are VSS (source voltage)
Be careful with the ugga duggas. Check the caps. Those are electrolytic and they tend to go explode when they get old. That's usually what fails on a board if the magic smoke didn't leave it.
There's a bunch of the IC on ebay.
Replace both driver chips, resolder R104 and 107 and replace the four electrolytic caps.
the other numbers wouldn't matter to much they use those for date code and batch id for most integrated circuits edit dip is the through hole dual inline package and soic is a surface mount version small outline integrated circuit
I would guess the number in the middle is just the date code and the last one just some kind of serial number...so doesn't matter at all
If I would have known it was this complicated I would have said $5K easy. I hate cutting bourgeoisie capitalists a break. I'm so ashamed I told you to charge them a lower price. I'll never forgive myself.
Maybe I should get into the Lens Edger repair business? ;)
You definitely should get into an industrial electronics repair business (preferably obsolete equipment as there you're customers will be entirely at your mercy) as you'd make a hell of a lot more money fixing business critical machines that you will fixing rusted out cars for broke people. There are a lot of machines like this. For example a CNC lathe, a CNC Waterjet or plasma cutting table. There is a whole world of industrial equipment that is computer controlled that HAVE TO WORK or people don't get paid. You're smart enough to realize this fact yourself. Time to start thinking about your future Ivan. 2000 era Fords and Dodges aren't where it's at. You're young enough to make this change now. Your wife works and you have no kids to feed. Time to get out of the muck and onto the paved highway. This ain't Russia Ivan here you have complete free will. Use it.
you make a very valid point, I have been told the same thing and still find myself working on old junk cars for little pay. I've spent so much money in schooling and tools, not to mention all the time to learn this trade that its hard to walk away. Companies that rely on one person or one machine should have realized this in the beginning and started saving for a backup or looking for a replacement.
While I agree that businesses should set aside money for upgrading equipment, since they do take depreciation on that equipment over the years, calling them bourgeoisie capitalists just because they asked someone they know to see if they could fix their machine (when the manufacturer clearly couldn't,) seems a little unfair. Sounds to me like they were willing to pay for the repair and when they struck out with the manufacturer, asked Ivan to see what he could do. Ivan should charge what the market will pay but to just charge extra for no reason, in my opinion, starts to border on an ethical dilemma (at least to me.) His wife works there. As long as they pay for his professional time, I don't see a problem and wouldn't consider them bourgeoisie capitalists.
I would be flattered if someone asked me to see what I could do with it. I'm guessing the outcome has already come to pass, but, I'd recommend getting a nice little desoldering machine and adjustable temp soldering iron, and work that into the bill as parts needed to fix it. It's so easy to damage the fine traces on these boards. I'd at least want a nice adjustable temp soldering iron, for sure. Don't go gorilla on the soldering iron. The chip is no good but you have to be real careful with the board or the whole project can be ruined. You'd be amazed at the difference between a cheap Radio Shack soldering iron and a nice adjustable temp soldering iron with soldering quality and board damage.
Johnaclark1: Have you bought and more importantly PAID for a pair of eyeglasses lately? BOURGEOISIE CAPITALISTS. I don't hate them I'm just trying to help Ivan become one.
Interesting
I would get a socket and put that on the board. That way you can easily unplug the chip and plug in a new one if it fails again.
my appology for the typos. this cell phone stinks
ivan there are companies that specialize in overstock,obsolete chips relays etc. many meddling ears ago i worked for a company that had customers that specified that type of stuff. A real pita to work with at best.
Unfortunately Im out of that business for a long time now and one of the companies we used is out of business. the other business was in Rochester NY , I cant remembee their name but their. aligan was. : We are the leaders on the trailing edge of technology
What a stud
I have been able to buy various semiconductors for my 40 plus year old audio equipment on EBay. Pretty amazing if you ask me.
Hi dear friend,we are un Venezuela en have the same machíne,we hace some trouble cause did not Star to cut,is possible that You can help us,have some mail to contact You,really really thanks
DIP = Dual Inline Package it has legs that go through the board to be soldered
SOIC = Small Outline Integrated Circuit. It is soldered to the surface of the board. Surface mount in other words. You can adapt surface mount components to through hole with adapters, but it's not really recommended.
www.digikey.com/en/product-highlight/l/logical-systems/surface-mount-adapter-kits
free glasses for life would be sweet .. but being paid $ 3000.00 for a $12.00 part and 5 hours diagnosis would be sweeter :)
When the time comes cut the pins off close to the chip and remove one at a time.
Now what would I cut the pins with?
Flush cut pliers. Link to Amazon: www.amazon.com/TDOK-TD-109-Cutter-Pliers-5-Inch/dp/B06W9NMMNK/ref=sr_1_2?ie=UTF8&qid=1506736713&sr=8-2&keywords=flush+cut+plier