Those are not possibly 4W resistors. They are either 1/2W or 1W, depending on how old the board is. I'd guess 1/2W from the size of the resistor and age of the board. So the 2W modern resistor is plenty good enough. There is no particular relationship of the wire gage and the resistor wattage. You can guess at the wattage from the physical size of the resistor body. The problem is that resistors of any given wattage have gotten smaller as technology has improved, so you have to guess based on the age of the technology. A resistor turns power into heat. That heat has to go somewhere. Think of the resistor body as a heatsink. The bigger the body, the bigger the surface area to radiate the heat, so a bigger resistor runs cooler for a given power dissipation. A resistor at full rated power runs almost 200 degrees C, which is *really hot*. So you usually over-rate a resistor by about a factor of 2 to keep the heat reasonable and not fry things near it on the board. The resistor is both a current limit and a fuze. Those DIP reed relays are only good for a few amps. 16 ohms at 24V (assuming output is shorted to ground) is about 1.5A. I assume the relay is rated at 2 to 5A, so this protects the relay. The resistor also limits inrush current when powering a relay load. Without the resistor you could get contact welding from the inrush current when the relay closes. My guess on why it fried: you mention the E-Stop switch was broken and bypassed. I suspect that the wires near the E-Stop switch got shorted to ground. Putting 36W (24V across 16 ohms) thru a little resistor like that would have popped it pretty quick.
That makes sense to me. I ordered some 1 watt resistors as well, and I contemplated installing them. But, I think it's fine like it is. As you say, the relay is limited in its current capacity, so the 16 ohm resistor would make sense. The builder does not know how the output will be used when the board is designed. Some applications may use all 1.5 amps. Thanks for your input!
Realistically those outputs are limited to something like 250ma at most. That would be 1W in 16 ohms, and for that the resistor should be a 2W resistor. Since I suspect the originals are at most 1W, the power should be limited to 1/2W continuous, or 175ma. You also have to consider voltage drop. 250ma and 16 ohms is a 4V drop, so you only have 20V to run the load.
l wilton That was some really good reading for only four small paragraphs. I really enjoy Wes' channel. Also If you have written anything else I would consider it a privelidge to read it. Thank you both.
Those Bluey Green Resistors of that size are usually "flame proof" and used as a current limiting and fuse all in one. The wattage looks to be 1W (old 80's vintage colour TV's were packed with these to protect different sections of the set eg Audio output stage, horizontal output and vertical output....... ) When thinking of low ohmic resistors as a current limit consider the limits of the circuit eg when will the most current flow ? A direct short to ground, the only real resistance then is your 16 ohm resistor, more common problems are shorts in wiring looms where smaller diameter cables are used and the total cable resistance can creap up to a couple of ohms. This in conjusction with the 16 ohm resistor will limit current to the loom and the load. I hope this makes sense. Kat.
To be a mechanic these days you must have a in depth knowledge of electronics and computers. Long gone are the days of "just a wrench turner". I was an ASE tech for years(couldnt make any $) and i fix Tvs washing machines computers etc etc. All kinds of things are related to electronics these days
Great video, tho a bit over my head. We had an electrical engineer on a new hydropower startup. Things just didn't work. The plant people started calling him "Jumper". He walked around with a wad of jumpers around his neck.. The back of the control boards had jumpers all over for years. I so enjoy watching your great diagnostic skills.
Super useful diagnosis protocols! Well done for getting it sorted . It is a pain if you can't get the ladder diagram for the machine you are working on ......
After watching 30 plus videos, I am very impressed with your knowledge of mechanics, troubleshooting, use of electronic measures (scopes), and electronic knowledge, especially complicated wiring diagrams. I would be very interested to know your background, training, schools, etc
Wes, I love your videos, especially the machine control repairs ones. I did another repair on my 1996 Bridgeport Torq-Cut 22 this week and it's stuff like your videos that give me the inclination to try such things. Which is incredible because I have no idea what I'm doing, but I keep figuring it out and coming out on top. This time the carousel motor for my toolchanger wasn't working and so I inspected sensors, relays etc, etc. Had a lot of false hypotheses but eventually noticed that I was getting the correct voltage at the board and not at the motor, and sure enough the 16/3 stranded cable to the motor was bad on one conductor. Makes sense because every toolchange that cable gets flexed and rubbed some and it is 23 years old. Anyway, thanks for the videos!
Awesome work! that brings back memories! I worked in a machine shop back in the day. I was p[atient and would look and find the problem. The field techs would come and diagnose it as a bad board never looking for a problem. I retired in 2009 after getting shocked by 600 volts which really screwed my back up. It was in a hyper-therm plasma cutter that could cut up to a 1-inch plate. we had 4 of these with a steel handler ad on. 4 commercial plasma /torch cutters, 4 presses. A 300, a 150, 100 and 2 fifties. 8 Haas vf? series. a couple of brother vertical mills, 3 horizontal mills, 15 welding stations, 3 robotic welding stations and about 20-30 support staff. When I started there they had hired me to service their trucks, forklifts and other small material handlers. The guy who worked there took an extended leave and never came back. I was happy just working on the trucks and forklifts. They hired an independent repairman who knew his shit and part of his job to train me up. It was an awesome job that I miss to this day!
Excellent : Clear and concise troubleshooting and analysis of the wiring schematic - nice to find the blown resistor and thankfully it’s a ‘90 machine without surface mount micro resistors - another machine put back into service rather than the scrap yard - well done.
Nice simple fault finding, one of your subscribers has already put forward a pretty good explanation of what may have caused the resistor over current (dangling E-Stop switch wires). Great professional repair. Thanks for sharing and best regards from the UK.
I really like to watch Wes work. On anything! And some commentators that are technically savvy really are an added bonus. And I like your technical explanations as you work. Keep up the great work and videos. Nice editing on videos. Cheers from Schuylkill County PA!
Great video Wes! Really enjoyed seeing another machine-tool topic, those are hard to find. I agree with @sombody-else below on the practice of adding fresh solder before desoldering, with the addition that I place a small blob of that paste-consistency flux (PCB-grade, comes in a little syringe applicator) on the lead at both steps (adding solder and final solder pull). That practice really reduces my time "on-pad" with the Hakko desoldering tool and seems to leave a nice clean (and even shiny) hole behind. There's a little more cleanup, but it seems to minimize the PCB impact. The practice I've evolved to is *always* add flux and don't depend on what's in the solder core to make it everywhere it needs to go. Anyway, glad you got it working :)
I don't do it enough to be any good at it. I did have to add some solder to get a good result. Seems that large components like resistors are really difficult, especially if the leads are bent over before they are soldered. I also think really small components are very difficult.
I have repaired a number of older vintage boards that use low ohm resistors to protect power circuits like a fuse. One 3 phase inverter manufacturer always used 1 ohm resistors, and they were easy to spot.
Yeah, many, many times I've had to put fresh solder on a connection before I was able to UN-solder it. There has to be enough solder on the joint to both transfer sufficient heat to melt all the way through, and provide a seal against the solder sucker tip. It can take an annoying amount of heat on multi-layer boards.
@@adamdnewman - I was led (pun intended) to believe that the hazard which the law was intended to address, was leaching into groundwater from discarded electronics. Same reason that leaded glass CRT's can't be disposed of like common glass?
If you lived in Oregon I'd suggest working for Oregon ice cream, we need good knowledgeable people like you who are willing to actually work. I have some good people but they get swamped and burnt out. All the others are clowns that can talk but not perform. Anyways, I enjoy your work, keep it up!
Good Electrical troubleshooting wes. On your new shop being out of town just takes a bit longer to run for parts. My friend put in a concrete floor and put in snaking pipes in the concrete and then just put in two water heaters. Very nice but with a lift you don't have to lay on the floor under your work as much as I do.
He's doing alright now, but at first... I was cinched up watching. I had to scream SINGLE BLOCK, 25% RAPIDS, DRY RUN ABOVE THE PART!!! I'm sure I was the exact same way starting since I was 100% self taught also, just didn't know enough to get that puckered yet. lol
Hey Wes. Good job on the trouble shooting. The only down side because you on sold this machine. I am guessing this was not a money making job for you. Thanks for taking the time to share with us. Peter.
Selling faulty equipment as a small enterprise, can put some strain on your very important customer relations. Big companies selling new products on the other hand, can use the customer as quality control freely, as everyone else seems to do the same.
Well it didn't take too long. The jumper wire had already been installed so I knew the contactor circuit could work. I just had to find the weak link. This old Tree is very simple. The newer machines are much more difficult. Most now have dual e-stop circuits. Some are using pulse signals that can only be tested with an oscilloscope.
Thanks for showing all the details of searching the electric failure. Great that you explained the E-Stop Security Circuit, that will mabee help me in future with a broke down machine. I worked a longer time in the repair center of a large company repairing electronic boards and we also had an automatic desolder gun, we aplieed fress solder bevor desolderin an component . The fresh flux in the solder makes it easier for the desolder gun to suck it in. Keep on going! great videos!
Hey, Wes, love all your videos no matter what you’re working on. I have a question for you. I have a Mori Seiki sl 150, 1996 vintage. I did not get a shop manual with it. What power of rotary phase converter do I need to run it?
That's pretty similar to the SL-20 I had. I ran it with 100 amps of 220V 3 phase. I imagine it would actually run with less if you limit the spindle acceleration ramp.
They usually use those resistors to stop relay chatter, when a relay is fired by another relay they tend to chatter and putting a resistor across the coil stops that from happening..
Theoreticaly speaking: if the line resistance in that branch somehow droped to single digits, then the 24vdc applied according to Ohm's law will be plenty to jack up the current flow beyond the maximum that resistor can safely handle. Personally, I believe it was a manufacturing defect in the resistor. I've seen plenty of cases like that "unexplained failure" back in the 80'-90's board repair shop. Those were the last glory days for surface mount PCBs. Miss them days.
Ahh ladder logic...I was an elecronic tech at a shop for 12 years. It was my job to keep a big Giddings and Lewis 60 inch horizontal boring machine running. It was converted to cut threads on large diameter casing pipe for the oil industry. Then the pipe was threaded together instead of welding. It was 70's CNC technology. Fun times...
The stripes on a resistor indicate the resistance value of the device and the precision ( whether it is 1%, 5% or 10% )of the device. Wattage rating is pretty much a physical size of the device.
Desoldering iron - there's a hole through the tip and a vacuum pump, sucks the melted solder out of the joint. Definitely wasn't expecting to see such a nice electronics bench tool in the hands of a mechanic!
those are definately current limiting-the copper traces are very small on this board so a short circuit would melt the traces and ruin the board! good design actually
Resistor is a surge limiting resistor. A coil with 0 current has 0 resistance so when you switch on its like a short circuit. What stops the coil being a short circuit is the magnetic field built around it which opposes the current flow. Without that resistor you could have a high current flow on switch on, an overlarge field build up causing a back spike. That in a computer chip is not nice.
Wes, Thanks so much for posting this! I have a Hardinge ST20 with a Fanuc OTC control that I can't get out of Estop. Machine comes up fne. But try as I might, I can't clear the Estop. I have used the wiring diagram to try and jump out terminals just as you did. Nothing. My machine's Estop circuit looks to be wired similar to yours. Maybe my problem lies in the I/O board as well. Going to try and look into tnis! Love your videos! Thanks again!👍
You just have to check all the components in the chain. Often you will find a bad thermister in a motor, or a heater is tripped in a contactor, or something like that. I had one throw me for a loop one time and I finally figured out that the chip conveyor was unplugged!
was thinking about Fanuc while watching this- zeroA/B/C/D fanucs use x21.4 as estop input, just thought it was kinda ironic the 214 wire was in the dynapath circuit too... seven months, assume its already fixed- on the old zeroes, its often age related failure of the estop button, the brown contact block on those fuji buttons are easily cleaned- remove it, take the terminal screws out, pull the terminals straight out, and the center actuator/contact/spring comes right out- dont lose the spring. just clean the silver pads and reassemble, good for 30 more years. zero membrane style op panels are kinda weird as the whole machine often runs into the m1b input/m2b output plugs, then the m1a/m2a go back to the io card... you can check for continuty from M1(33) [+24] to M1(18)[estop] IIRC by just unplugging M1A connector and checking the op panel connector half. note though it will also have the M1B(18) pin feeding into the loop too- usually from overloads/overtravel string on machine side- much like this dynapath
Great economy means lots of work, we have not ever had this good here in California and we have been through the early 70's mid 80's and the DOT com crash 2001 tight credit and then the 2006 /2008 meltdown, so yes the neighbors being busy sounds great to here from you as noisy as they are. This is of course until you fix and then hit the e-stop button for the economy Wes. Lance & Patrick.
You're going backwards you should start to your right side at the run contact relay and see if you're getting the signal there if you're not then you go halfway down the circuit and check for your signal there if no keep going back if yes go back towards the relay you should be able to find your open circuit within three points. Always start at the output end of your circuit and half and half again until you get to your fault. Starting at the beginning input and moving forward will get you there eventually but it will take a hell of a lot longer time. Always check your power source and then your termination end. And then go to the middle etc. Work smarter not harder. This is coming from a retired industrial technician with 50 years experience. And why the hell did you replace the switch was it bad or was the idiot before you just shotgun jumping stuff out? Whenever people have been in that piece of equipment messing around always return everything to original stock condition and go from there. Otherwise you'll spend hours on doing other people's donkey crap. You'll be surprised how many times just putting it back to the right way fixes the problem. Some dummy might have been in there looking in the wrong place jumping stuff out. And then going and finding the problem and leaving the garbage behind. That's especially true of inexperienced monkeys with four-year degrees and no background. It's like car mechanics that have 50 badges on their shirt in 2 weeks experience they know how it works but they don't know why it don't work.
Of course lead size is related to current, but different manufacturers may have different size leads on the same wattage resistors. I've seen this many times. Older resistors tend to have larger leads for any given wattage. (I've been in electronics for 60+ years.)
Their purpose would be both. Current limit the solid state relay and create an overload fuse in case of a failure. Solid state relays need current limiting due to their low impedance.
IMO: One of the purposes of using an electromechanical output relay is that there is really no need for a protective circuit. Adding a limiting resistor is silly and it has introduced more ways to fail. Resistors burn out over time and it may very well be exactly what happened here. The cost of board repair lies mainly in the labor and replacing the relay is not more difficult than changing the resistor. The fact that jumping 24 volt to the board output made it all work makes one wonder what the relay is even there for? Lesson: If You want to make reliable boards do not introduce superfluous components. 2) If the purpose of the resistor was to interrupt overcurrent and shorts one can use a special "zero-ohm" fuse-resistor that looses the connection quickly without setting fire or burning the board. Using a high wattage resistor is clumsy and counterproductive. If the purpose was to make a cheap say 100 mA current protection one elegant solution is to use a PTC resistor ("auto fuse"). 3) There may also be an issue with lacking current protection in the power supply. Kind regards
@@Citronitroify I agree 100%. Likely this board was made for multiple applications. Though the use of these components here seem excessive and over-engineered, in other applications these relays and limiting resistors may play a significant role. Often times in manufacturing, components are chosen not because they are perfect for the application, but simply because they satisfy the criteria. The manufacturer may have been using this board in other applications and by utilizing it here, allowed them to reduce their overall part inventory. Though I disagree with this practice, I do understand why it is done.
hadnt thought about those in a decade...relays disguised as chips...the old Fanuc Six series used a plethora of them on the IO cards- 99% of the failures were from contacts sticking, and 99% of the time 'fixing' could be done by simply strumming a plastic screwdriver handle across them... the little vibration will almost always free them up. the six was a helluva durable control, those little relays were its achilles heel. back in 1996 or so, I built a test rig and wrote a ladder(have one of the few 'suitcase' plc programmers still in existence) for a buddy who owned Tennessee Industrial, one of the bigger Fanuc repair shops- used one of the big gold 'connection unit adapter' wire wrap boxes, gutted/rewrapped so inputs on front board fed by outputs on rear board and vice/versa, put a led grid that lit up relevant row/column of the relay location being tested... (and load resistor to pull a few milliamps of current) it ran a continuous loop looking for missing inputs, shorted inputs(the six used 4 point input buffers- a failed input usually tied all 4 together) or stuck outputs then stopped with the led showing what relay to change... they did board repairs, always let boards run 24 hours chattering away to test...far as I know they still use it. hadnt talked to them in a year or three... things 20 years old now LOL, had over 1/4 mile of the 30 gauge wrapping wire in it :)
I have a question, why is the chasis of the machine connected to 0V? Thats how it fried the resistor ok, but why is 0v connected to ground in the first case?
@@WatchWesWork Without a diagram you could start by pulling boards to look for obvious faults and you would have seen the burnt resistor. I think you were lucky with this one. I often get multiple cascade failures in the logic/control chip systems on things I'm fixing.
This may not be relevent, but I first thought of it as something humorous; For instance- Joe Pieczynski shared proof on video of him de-fouling a spiders legs one at a time with some tweezers and an exacto Knife. (The Spider was clearly assisting in the operation.) In a machining environment I wonder just how fine a chip could possibly become entangled IN or TO that type of "fuzz" I saw him clearing from I think it was a good size Wolf Spider. One documentary I watched once showed a pretty damn big Floppin Spider large enough to kill a small chicken. Maybe you CNC guys could estimate the guage of the wirey birdsnests generated with a really fine finish cut? In the name of Science, or a good laugh. ( If a spider crawled accross the e-stop part of the board.)
Okay you got a 2 watt resistor so it'll handle 0.833 amps which is 83.333 milliamps anything higher than that will blow the resistor so in essence is current limiting between the diode and the relay basically designed to protect the relay from power surges or backfeed and only theory I got is apparently you had a power surge or backfeed to that resistor now and I don't know why the diode didn't blow but apparently it didn't so the resistor blowed before the relay got burned upI don't know how old is journeyman CNC 425 machine is cuz I'm not familiar with that machine but I do know resistors will burn out over time from everyday use that's not a possibility it just could have been time for to go
I have soddered many thousands of boards over the years and never have I seen somebody Sodered like That you've done pretty good but they do have External flux that would help you a lot in Sodering. You should never put paper or plastic anywhere near a PWB
You got the general idea is a current limiter the higher the resistance the lower the amperage through the circuit the lower the resistance the higher the amperage the best way I can explain it to you
Rookie mistake. you should have put the clamp amp meeter nearest the power supply as possible. And wriggle the wires this would tell if you have a short to ground. no point testing amps at the load.
What you just did is monkey around with a perfectly good circuit before you check your input to that circuit. Now you've gone to the board that supplies that input because you don't have it there. Well I don't know how to break this to you but the output from that board only switches well on when the input logic to the board signals to turn that circuit on. So you need to check that before you start pulling boards more time wasted. Guys like you used to make me look like a genius. Put down the schematic and get yourself a flowchart. You'll be able to troubleshoot a lot quicker. That is if you know the difference between a diagram, a schematic, and a flowchart.
The current limiting resistor is just there in case somehow there's a wiring problem. Either a fault OR someone does the jumper wire test without first removing the connection to the control board like you did.
If the wire was shorted to ground, it would cause the relay to open (un latch) and the machine would go into E-stop. There are no fuses in the circuit, but the 24VDC power supply has internal current limiting. It will shut down if it draws too many amps. If the wire was open, the relay would not close at all. The beauty of the latching relay is that any intermittent wiring issue will cause the relay to un latch and basically shut down the machine.
