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This is a faulty control system that was sent to me by Bjorn. When his new printer failed the supplier simply sent out a complete new pair of control boards as it was the cheapest way to guarantee a fix.
The system is completely dead unit with the display pulsing briefly at power up and drawing a high supply current.
Many of the modern units take a modular approach to allow swapping out specific sections of circuitry. It's often faster and cheaper to just swap in spare modules until the unit starts working again. But in the case of specialist machines or obsolete equipment it's useful to be able to diagnose a fault to component level.
It's easy to forget that things like 3D printers and cutting lasers used to be very expensive industrial machines. They've become so popular that you basically have a full blown industrial machine on your table.
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A set of boards out of a 3d printer - these were sent to me some time ago by bjorn, who said here's the faulty 3d printer board. I promised to send you it is a control board for an annette a8 3d printer after i changed the potentiometers. It will potentially there after i change the potentiometer to increase torque the motors the board refused to turn on properly tech support. Told me a little light should blink, but even that doesn't happen um.

Basically speaking, what happened is the board failed and he got just because that was easiest for them to do this. They just sent a complete set. They did the parts kind of thing it's just easier for companies to do so. Let's investigate what's happened.

If i just turn this power on here now watch the display and the lights. If i turn it on a brief blink from here, nothing, it's sinking an amp. The voltage has dropped to 4.33 volts. I'm gon na leave it for a second, because that means something is heating up on the board.

Right. Tell you what let's uh, let's get the thermal imaging camera into it? Let's get the thermal imager in just. Let me boot this up. Booting up my thermal imaging phone because i'm very close to it, i can actually see a hotspot right away.

Oh i can see hold on. I can see the voltage regulator is hot. What is that over there? That's hot finger in front of it. Oh, that is hot.

It's one of the stepper motor drivers rightio, let's investigate i'll turn the power off. Now this stepper motor driver has failed. Now this circuit board i'll show you a picture of the circuit board, it's easier to point at because it's ultimately bigger. So i'll put this down here, i'll just zoom down onto that, we have the five stepper motor outputs.

We've got the x motor y motor, two zed or z motors and an e motor for the extruder. This is the one that's failed, and it's right next to the potentiometer. I wonder if, while adjusting this tiny potentiometer screwdriver slipped and it's bridged onto these capacitors, so what i'm going to do now, i'm going to bring the circuit board in here. I want to de-solder this and see if it clears the fault, but it's got that little heat sink glued onto the top, which is going to make it quite hard to.

I wonder if i can do this without damaging the circuit board. Can i i don't think i can get anything flat underneath to try and cut through that is the silicon going to. Let me slide the heatsink off. Yes, it is by pushing down sliding that that's giving access to the chip right.

I should have thought about this. In advance, i could have got the soldering iron on, but i'm going to pick the silicone off this chip as much as possible. I'm going to get the soldier iron on and i'm going to try and heat this up. The hot air gun um and get some flux under it to try and melt it and we'll see if we can get that off one moment, please: okay, i think i'm ready to have a go at desoldering.

This. The chip is a 4988 et, which is a fairly standard. Well, it's a variant and a standard stepper motor driver. I'm going to start by putting some flux around this, i'm going to just splice it all over the top of it.

I'm going to make a big puddle around there. It always helps flux. It kind of softens the soda it kind of like mates on and just gets the heat in, for some reason just helps. I've got a heat gun, i'm going to start heating this up and it will take a bit of patience.

I don't have much patience, maybe i should have used and maybe i should have used a gel flux as opposed to that right. I'll just have patience. I'll point at this now just try and blow all the other components off the circuit board. As sometimes happens, i shall undulate around and round and see.

If it's now is it going to move, is it moving? It doesn't help that there is silicon in the vicinity of it. I can see the solar light getting a bit shinier. This is good. This is good.

Oh, it's all radio, let's uh clean that up with the soldering iron and some de-soldering braid, i'm trying to find my sorting braid here it is so i shall put some fresh soda in that. Looking for my fresh soda here. It is so just basically get it all over those pads. This kind of helps clean things up a bit and i'll use plenty of flux.

Let's get loads of flux in this, let's make a huge mess. Oh look at all bubbling away nice and i shall just scrub this gently around without removing all the pads off the circuit board, all the tracks and that will hopefully mop that up right, tell you what that looks: pretty clean uh now i'm gon na power up And we'll see if the system starts one moment players right, let's test it. The chip, incidentally, is uh 4988et. The closest i could find to that was the allegro a4988, which is a very smart little chip.

It's a minimum set of pin count for the microcontroller stepper driver, which does things like it's got a little capacitor there charge pump that it steps the voltage up inside for solid driving the mosfets inside and it allows micro stepping of the motor. But it takes all the sort of the hassle away from the mic controller. My controller - all it has to do is say, go in this direction, go a number of steps. That is, it very neat little chip available if you buy them in bulk for about 10.

Well, you can either buy one for 10 pounds or you can buy 10 for 10 pounds. It's one of those things very neat to write. Tell you what let's say hook this up and what all i'm really looking for here is for it to boot. Up if it boots up, we know we've got the power rail back, so i shall plug the display on and i shall power tap now.

It's booting a net or annette 3d printer welcome to annette printer ready. One thing it doesn't do. Then it doesn't check that the chips are actually there. It doesn't do a self-test, but that's fine a little reset button.

Let's press it! Oh it does reset it. That's nice uh! So well, i don't have an anec printer, but if i did is the fir, the next step would be to buy one of those chips and replace it put the little heatsink on with silicone compound the silicone adhesive. And then i try it worst case scenario. The data lines may have been affected.

If the voltage had been bridged onto the data lines, it could have knocked them out, and so it's worth mentioning these little tiny, trimmer potentiometers, if you ever do a lot of adjusting of them. Well, even if you have one piece of equipment that needs them adjusted, you can get trimmer tools with plastic tips and the advantage of plastic tip. Is you can't short stuff out also they're, pretty common because they used to be used for tuning coils, inductors and variable capacitors, because the non-metal nature meant they didn't interfere with them, but there we go. I would say that at this point in time, we know where we are and uh the next step would be to actually get the chip and put it in and then find a suitable test subject.

Even just sticking a motor in there would probably work and just see what happens, but there we go that's as far as i can go at the moment. I'm happy that i've proven that that is the faulty component.

12 thoughts on “Diagnosing a dead 3D printer controller”
  1. Avataaar/Circle Created with python_avatars A Stevens says:

    i can almost be sure i would win a bet that the (z) carriage axis was raised or lowered manually and abruptly, and the induced current blew the super cheap a4988 trash driver commonly put in fire boxes like the anet. ill also accept that it just blew because its a horrible driver for 3d printing.
    if you look at the marlin source code, that is the default driver setting, and it expects you to change it if using a quality driver, like the TMC series.

  2. Avataaar/Circle Created with python_avatars Winston Smith says:

    Would you really Big Clive ? Buy another chip ? when you now know a current level has been exceeded and has tobe monitored whilst adjusting the pot and you don't know where or by how much ?
    My advice to anyone buying stepper motor drivers is , put the toys away and look to Parker Controls are the dogs bollocks and British is BEST. Leave it to the experts and stop making rubbish tips.

  3. Avataaar/Circle Created with python_avatars Overlord says:

    Great to see you have a go at something i've actually got and actually repaired my self multiple times also lol

    I've got 2 of these things, actually ones been converted into an extremely quick CoreXY style printer. They're extremely sensitive though to back EMF and if the original owner didn't short the pot or caps, the other main reason the driver probably died was manually moving the stepper motors (and inducing current back into the drivers). Happens all the time.

    These drivers are terrible bog standard cheap drivers slapped on many different chinese printers. If you were ever going to fix this board you'd do your self a favor and solder in a much better driver (lots that aren't much more expensive but offer so much more control while still being electrically compatible).

    Personally i killed the ATMega on 2 of my boards with a faulty USBasp flasher (Didn't know it'd go bad but it fried 2 boards…) luckily again those atmegas are cheap as chips, did the old cut the legs/desolder leftovers trick and fixed them both. Next time one dies it'll be board upgrade time i think

  4. Avataaar/Circle Created with python_avatars thumbwarriordx says:

    I wouldn't actually recommend doing work on that flimsy board because its traces are basically spring-loaded when it comes to peeling up off the thing.
    But it is entirely possible to bypass a stepper driver and use a replacement on it, I have unfortunately done it.

    Sent 12 volts into one of the microcontroller pins too, whoops. Luckily if you flash it with your own firmware, cut some traces and reroute around the 12v mishap it can be repaired with the single spare pin on the micro.

    But I also solder bridged the spare so stubbornly to another pin in the attempt that I had to reclaim the Z-axis enable wire, attach it to the X/Y enable wire and make further adjustments to the firmware.

    TL;DR Bjorn was 100% right to ship it far away and get it out of his sight.

  5. Avataaar/Circle Created with python_avatars legalsolutions07 says:

    I just watched your Simple Guide to Electronic Components and I enjoyed the clear explanations. Question: Suppose you have 220v three phase current that is powering a 220v three phase 3/4hp motor that drives a pulley but is directly connected to some circuit boards that run out to a power cord. Can you tell me if the values of the electrical components on such a circuit board are dictated by the 220v three phase current that is powering the motor? I'm trying to determine if I can use the same circuit boards for the same application with the same electrical components but power them with 110v single phase current and replace the motor with a 110v single phase 3/4hp motor?

  6. Avataaar/Circle Created with python_avatars David Evens says:

    The frequency with which the stepper motor drivers is one of the two main reasons that some 3D printer control boards have them on daughter boards. The other is you need to change the drivers to use much more (or less) powerful steppers, such as for building a 3D printer that can print large things, like chairs. Not chairs for doll houses, chairs for your house. Or, for that matter, the more experimental printers for doing whole buildings. So far there's no provision for installing plumbing and wiring by machine (getting the structure to reliably print properly is the current objective of most projects) but even if it just eliminated most of the labor from putting up concrete walls, it would be a substantial savings in labor.

  7. Avataaar/Circle Created with python_avatars Eremon1 says:

    Hey Clive, I'm curious if you've heard of Ellumiglow or any of their specialty lighting gadgets. They have some odd stuff I wouldn't mind learning about if you find any of it interesting. Cheers from across the pond.

  8. Avataaar/Circle Created with python_avatars Gerald Tompsett says:

    The FLIR camera since about 2001 has been one of my primary fault detection tools helping me zero-in without testing each component with a meter or scope. I just wish they were a bit cheaper and there was a "nice" phone with one built in.

  9. Avataaar/Circle Created with python_avatars Fluffy Blue says:

    I have an Anet with that exact same board. It's still going strong. Probably because I didn't fiddle with that trimmer pot. I just flashed it with Marlin firmware so I was able to make it work with the BL-Touch sensor for automatic Z-calibration. I also added a bigger mosfet for the heated bed.
    BTW, what exactly is set by that pot? – EDIT: found the answer in the comments.

  10. Avataaar/Circle Created with python_avatars ian bertenshaw says:

    Keep the LCD board as it is useful and peg the rest in the bin ! it is old shit technology with crap drivers and not worth the trouble of reviving it . If he played around with the pot he may have had it set too high which kills 4988 drivers pretty quickly and as there is only one pot it is the one connected to the burnt out driver – metal screwdriver can short out the pot internally .
    Would have been better to use this excuse to upgrade to a better board with 32 bit chip and silent drivers .

  11. Avataaar/Circle Created with python_avatars kev4241 says:

    the metal trimmer screwdriver gives an easy clip on to monitor the Vref. certainly don't want it skittering across the board though. for A4988's the 2208 / 2209 are far superior replacement. i'd certainly have to trash the board, lacking the surface mount chip removal skills shown here

  12. Avataaar/Circle Created with python_avatars harshbarj says:

    That board REALLY needs a firmware upgrade. It has the default firmware. I have an A8 and with a few physical upgrades and the firmware upgraded it's a very safe and reliable printer. I have had mine now for about 4 years. Never been a problem.

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