Following wires on the mainboard in a broken FormLabs Form 1+ laser resin 3D printer, I found harnesses leading to several components mounted on the front panel. There is a sensor to detect if the lid is open. (Or more technically, if a magnet is nearby. A magnet is embedded in the lid.) There is also a button combined with embedded LED illumination. And finally, the dot matrix display.

When this printer boots up, a short logo animation is shown before proceeding to display text, indicating arbitrary dot matrix graphics capability and not restricted to alphanumeric character display of a built-in font. Which is great for flexibility but would also mean it is more complex to operate.

After removing four tiny hex screws I could pull the display circuit board free. (Promptly losing one of four plastic spacers between the circuit board and front panel.) Now I can confirm its blue color came directly from the display and not a tint imparted by front panel plastic window. We also see the circuit board is a FormLabs custom breakout board labeled with:

FORMLABS, INC.
DISPLAY BOARD REF 01
334056-01

But what is that module hosted by the board? I couldn’t see any identifying markings as-is. Maybe there are some on the back? The display module is held in place by four twisted rear metal tabs that I could straighten out with pliers, freeing the module.

I had noticed the pixel illumination didn’t look like backlit LCD, and here we see it very clearly marked as an OLED unit. Nice! Printed on the back were the following information:

PG-2832ALBM
P1471277-20-D14

And my search for that text came up with… nothing. Quite disappointing! I went on the internet to see if anyone else has identified this OLED module but didn’t find anything definitive. What I found was “Possible OLED display swap/spare” on the FormLabs user forums, posted by someone before they even received their Form 1 printer. They speculated it might be an NHD-2.23-12832UCB3 by Newhaven Display, which has a SS1305 controller. Sadly, they never returned to FormLabs forum to confirm their speculation, so I guess I’ll have to try that myself.

FormLabs circuit board has 10 IO pins in two rows of five. Newhaven Display’s website shows a very different breakout circuit board of 20 IO pins in a single row. But this difference could be explained. The display has very flexible IO configuration options: “This self-illuminating module has 6800/8080 parallel, serial SPI or I2C interface compatibility.” A custom FormLabs circuit board would only need to accommodate the interface they actually use in the product, ignoring pins for other interface options.

The collection of components on the FormLabs board looks broadly similar to the Newhaven board, though missing a few parts that could likewise be explained by supporting just data one interface instead of several. I would feel better if there’s a match between information printed on the OLED module itself and what’s listed on Newhaven Display website. But I felt more confident after looking at the thin FPC ribbon cable connecting the OLED to the circuit board: They are both 24-pins and have a very similar layout, including a truncated pin 4. Furthermore, they are both printed with the text:

E308847 F-D 1 94V-0

If these were two different displays, they’re using the same FPC ribbon cable so there’s a chance they use the same control protocols. Newhaven Display website says they welcome custom orders so maybe PG-2832ALBM is a FormLabs custom derivative of 2832UCB3? Either way, it is a promising starting point for a deeper look.

I turned on a broken FormLabs Form 1+ resin laser printer without its rear panel so I could poke around. I started with cables (POWER, X SIGNAL, Y SIGNAL) between its mainboard and galvanometer control board, because that’s where things broke. But now I have a better understanding (and even a long-shot idea to try) I came back to measure voltages of wires on the remaining mainboard connectors.

The Z-axis linear motion actuator (Z MOTOR) is driven by a bipolar stepper motor with two phases and two wires for each phase, the four wires labeled A+/A-/B+/B-. The resin tray peeling actuator (TILT MOTOR) is physically a very different motor but driven in the same style. Z-axis limit switch appears to be an optical interrupter which can be more accurate than the physical contact microswitch typically used for limit switch duty in FDM printers. It has three wires. One end has continuity to ground, the other end measured +5V while the printer is powered up. Middle wire measured 0.06V when Z-axis is positioned at top, and 3.7V when Z-axis is lowered.

As part of laser eye protection, the printer stops printing if we open the lid. Detecting this condition is the job of a (likely Hall effect) sensor just under the lid along with a magnet embedded in the lid. The magnet sensor plugs into the connector labeled INTERLOCK on the mainboard, with three wires colored black, blue, and red.

Wire Color	Volts DC (No magnet)	Volts DC (Magnet nearby)
Black	0V (Ground)	0V (Ground)
Blue	11.18V DC	0.02V DC
Red	11.18V DC	11.18V DC

Speaking of that laser, I had hoped to see a diode module with two wires positive and ground. (Example*) But LASER connector actually had four wires: red, black, blue, and yellow.

Wire Color	Laser Standby	Laser Illuminated
Red	11.18V DC	11.18V DC
Black	8.55V DC	6.6V DC
Blue	5V DC	3.3V DC
Yellow	0V (Ground)	0V (Ground)

I’m sure those voltages aren’t the whole picture so if I have the ambition to drive this laser module myself, I have more investigation ahead.

Next connector is BUTTON for a gorgeous illuminated metal button on the front panel. Four wires support this button, two for the LED and two for the switch. Red wire is LED+, gray wire is LED- (wired to ground on this circuit board.) Yellow is pulled up to 3.3V on this board and when pressed, yellow wire shorts to black which is wired to ground.

The final connector is a little more complex. It is a 10-pin (2×5) IDC ribbon cable for the front panel display. Probing that display will be a project all by itself.

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(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

The laser galvanometers on this FormLabs Form 1+ resin laser printer no longer move, which rendered the printer useless. Probing voltage of wires leading to those galvanometers weren’t as enlightening as I had hoped but hinted that actuator position sensors were analog. Earlier probing of wires between printer mainboard and galvanometer control board, I also found mainboard commands were analog voltages.

With these analog inputs, I was confused by the fact I found no analog-to-digital converters among the list of ICs. The STM32 microcontroller has but a single ADC channel. And even if it had enough channels, I doubt they’d be fast or accurate enough. (Built-in ADC peripheral proved to be limited when I used a ESP32 to measure voltage, and when I used an ESP8266 to measure temperature.) I found many digital potentiometers and a two-channel SPI-controlled DAC for converting digital commands to analog voltage, but not the other way around.

I went online to look at other galvanometer control boards. Looking at this unit (*) and this unit (*) found a few commonalities. They have six wires leading to their galvanometers as well, hinting at a standardized system or at least a convention. I see they also want positive and negative supply voltages, which matches what I’ve seen. I also noticed they want different input voltage ranges, and their galvanometers don’t operate with the same mechanical ranges. (Movement in terms of degrees of rotation.) Dashing any hope of a direct replacement.

They also have 6 or 7 potentiometers on board for tuning, and this was my “A-ha!” moment. I saw similar potentiometers on the teardown of a Form 1, but such manual tuning potentiometers are missing here. This is what the STM32 and those digital potentiometers/SPI DAC are for: instead of manual tuning control with potentiometers, the upgraded Form 1+ galvanometer control board uses a STM32 to manage those parameters using those SPI-controlled digital potentiometers. The high-speed control loop is still an entirely analog process built out of those quad-pack op-amp chips.

Looking at this system with new knowledge, I see a tempting possibility. When I turn on the printer, I see a few brief LED flashes on the galvanometer control board as if STM32 booted up. Probing the 3.3V regulator (component U5) I saw it received +24VDC input and output the expected +3.3V DC for digital logic. Looking at the burned-out power connector, I saw the drama happened with the purple wire which I now know carried -24VDC. Perhaps this damage meant the board no longer has negative voltage and that’s why analog control system stopped working. What if I soldered the purple wire to some other location on the -24VDC plane? Say the input leg on one of two L79 negative voltage regulators? There’s a good chance it’ll only recreate the electrical fire, because I have not fixed the root cause of whatever caused that fire. But I see a slim chance rerouting -24VDC will get the galvanometers running again.

While I contemplate this potentially destructive experiment, I will look at other parts of this printer starting with the rest of those mainboard connectors.

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(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

I’m learning what I can from a broken FormLabs Form 1+ laser resin 3D printer, and it was instructive to probe voltage of wires between its (apparently functioning) mainboard and its (definitely toasted) galvanometer control board. Since I had my tools ready, I thought I’d take a look at voltages of wires leading to those galvanometers themselves. Even though they’re not moving anymore I had little to lose and hoped to learn something.

There weren’t many markings on these galvanometers. There are two stickers on both. On a flat end is a sticker with “ct-pass” probably for quality assurance during production. On the side of the cylinder is another sticker. One read “1411-0765 X” and the other “1411-0985 Y” Given that the X and Y axis are labeled, these are probably not part numbers. But what else would they be? Maybe something from the calibration process? I might see more markings if I remove these galvanometers from their aluminum mount, but I didn’t want to do that just yet. In the remote chance I could get things working, removing the galvanometers would ruin their factory direction calibration because I wouldn’t be able to put them back exactly in the same place.

Electrically speaking, from galvanometer Wikipedia page I knew a coil of wire to be involved, and there should be some way to read current position for closed-loop control. Examining the thin circuit board hosting the connector, I see the white and red wires on one end routed to one side together, a candidate for coil wires. Remaining four wires were routed together in a different direction, and I guess they are involved with position sensing in some way. Perhaps a high-resolution quadrature encoder? Or perhaps the four wires communicate position digitally via I2C or SPI? I did see a lot of chips on the control board communicate using SPI.

Turning the system on, I measured the following standby voltage values:

Wire Color	Volts DC
Yellow	-0.044
Red	-0.026
White	+1.328
Black	0.015
Red	0.015
White	0.040

Not terribly informative by themselves, sadly. I didn’t want to probe these voltages while the laser is shining, out of concern for my eyeballs. But I was curious to test my hypothesis of position sensing. Using fine-tipped tweezers, I rotated the output shaft while watching voltage values. The yellow wire showed a tiny change that correlated to shaft position: from -0.014V to -0.078V. The adjacent red wire showed a larger range, from 0.044V to -0.235V, also correlated to shaft position. Both of these are tiny changes in voltage, but the fact there’s a repeatable correlation of voltage rules out quadrature encoder or digital data communication. This is an analog position sensor of some type. If it were like potentiometers I’ve dealt with, then at one end of the range of motion either yellow or red wire should get up to +1.328V provided by a white wire. But it didn’t, so something else is going on. These observations aren’t enough for me to fully understand workings of this board, but enough for me to formulate a few guesses.

Despite some concerns, I’ve decided to poke around inside a broken FormLabs Form 1+ laser resin 3D printer while it is running. I think it’ll tell me more about how it was supposed to work, because I didn’t learn very much from just a roster of ICs. But it still wouldn’t tell me everything, because some of its current behavior would be as intended while other behavior would be wrong because the printer is broken. And as my only example of the species, it might be hard to tell which is which.

Before I powered it up, I probed around for all the ground wires. Since the printer is powered by 24V DC delivered through a standard barrel jack, it was least easy to probe for continuity to ground. There was even an exposed pad on the main processor board labeled GND. Knowing which wire is ground for each connector established a baseline for voltage measurements once I turned the printer on.

The first surprise was on the GALVO POWER connector. It had three wires colored red, black, and purple. Black was known to be ground. Red was expected to be +24V DC, which was confirmed. I didn’t know what to expect for purple, and it turned out to be -24V DC. Negative voltage! Something I rarely see but it would be consistent with the presence of a ST Micro L79 negative voltage regulator delivering -15V. Which is a mirror match for the L78 positive regulator taking +24V DC and delivering +15V DC. Separately there is an On Semi NCP1117 delivering 3.3V for digital logic.

As for GALVO SIGNAL, it had three wires colored black, white, and red. Again I knew black was ground from earlier probing. Once the system was powered on, I saw white wire voltage stayed pretty consistent at 2.5V DC. The red wire was where interesting things happened: It varied between 0V to 5V relative to ground (or -2.5V to +2.5V relative to white wire) while this printer went through the motion of printing, blissfully unaware its galvanometer control system was fried. Plotting X and Y galvo signals against each other on my oscilloscope’s XY mode, it sure looks like a laser draw path. That is, as long as we ignore that diagonal noise I blame on my beginner level oscilloscope skill. Anyway, noise aside, it shows this 0-5V (Or -2.5 to +2.5V) analog voltage is how mainboard commands galvo position. This scorched control board couldn’t translate those commands into galvanometer movement, but I wanted to see if anything is getting to those galvanometers at all.

Exploring the guts of a dead Form 1+ laser resin printer. Looks like galvanometer commands are analog voltage level: oscilloscope plot on XY mode resembles laser beam path. pic.twitter.com/7FvrgSRF1k

— Roger Cheng (@Regorlas) September 9, 2022

Curious about what I could learn from a scorched laser galvanometer control board, I looked up all component markings I could find. That gave me a few pieces of a puzzle, but I’m missing many more pieces and I don’t have a guess as to how those pieces fit together. In the interest of getting more data, I thought I would probe around while this FormLabs Form 1+ printer is powered up.

The biggest danger is a laser at the heart of this laser resin printer. This whole printer is classified as a Class 1 laser device, which means it is safe to use without eye protection. But that guarantee of safety only applies when used as intended. If I’m going to probe its circuitry with panels removed, I lose protection provided by those panels. Bypassing such protection means I have to be careful not to damage my eyes. Anyone who plans to try this as well: please be careful!

Working with lasers is especially dangerous if they operate at a wavelength outside human visible spectrum. We have evolved a blink reflex to protect our vision, but it wouldn’t work for wavelengths we can’t see. Thankfully, 405nm is within human visible spectrum (it should show up as an intense blue or violet beam), so I still have my blink reflex as a final line of defense. Why 405nm? Apparently, this wavelength became popular because Blu-ray drives drove R&D and economies of scale. I don’t know about power levels, though. I would guess resin printing runs 405nm lasers at a higher power level than reading Blu-ray discs (60mW as per Wikipedia) but I have no data to support that guess.

There’s another interesting data point I want to investigate: the printer was happy to run through its printing process with a dead galvanometer control board. Such behavior tells me something is running as an open-loop process, operating without feedback that its laser beam wasn’t being steered. I knew stepper motors used in cheap FDM 3D printers are open-loop devices, where the printer control board sends motor pulses without knowing if there is actual physical motion. But laser galvanometers are closed-loop actuators, so something else is going on.

Despite my wariness of a laser operating at unknown power levels, my curiosity motivated me to power it up and poke around.

This Form 1+ laser resin printer has a scorched galvanometer control board, and replacements are no longer available from FormLabs. I don’t have any background to make heads or tails of a laser galvanometer control board, but I might get a vague idea and learn something by examining its collection of components. Here’s a roll call based on markings on those chips.

The board controls both X and Y axis galvanometers, probably why the middle section of this board a pair of identical assemblies.

Starting from the upper left, component U4 looks to be the brains of this operation: a ST Microelectronics STM32F030K6T6 with its ARM Cortex-M0 core running at up to 48MHz.

U5 in the upper right is an On Semiconductor NCP1117, a low-dropout (LDO) voltage regulator marked with 17-33G indicating it outputs 3.3V. This would supply power to the STM32 and other 3.3V digital logic.

Back towards the centerline, U6 is a Microchip MCP4802 digital-to-analog converter (DAC) with dual 8-bit resolution channels controlled via SPI.

Just below that is U7, a TI TL032 dual-channel op-amp.

On either side of U7 is a collection of 8 chips, four on each side. (U104, U105, U106, and U107 on the left. U204, U205, U206, and U207 on the right.) They are all marked with Microchip logo and 41H51103, which I found to be a MCP41HV51 SPI-controlled digital potentiometer. In section 11.1 Package Marking Information of the MCP41HVx1 datasheet, 41H51103 is identified as MCP41HV51-103E/ST variant.

There are a lot of surface mount passives in the center section with two copies of the layout left and right. Each copy gets a trio of chips marked with On Semiconductor logo and MC33274ADG. These MC33274A chips are each a quad-pack of op-amps. Each side has an additional component that is mounted vertically so we only see their top here.

Going back to an earlier picture focused on the burnt and melted connector, we can see one of those vertical standing components clearly on the right. They are On Semiconductor BD139 NPN power transistors.

Three components are bolted to a heat sink at the bottom. To the left is a single Texas Instruments LM1876. It is a dual 20W audio power amplifier. Adjacent to that amplifier are a mirror pair of ST Microelectronics voltage regulators. The L79 negative voltage regulator accept up to -35V DC and output a regulated -15V DC. L78 is its symmetric positive voltage sibling, accepts up to +35V DC and output a regulated +15V DC.

Those components are major pieces of my “how did this board work” puzzle, but I’m still fuzzy on how they fit together. If I want more data, I’ll have to probe around while the system is powered up and I’m not entirely sure I want to do that.

Diagnosing why a FormLabs Form 1+ resin laser 3D printer wasn’t working; I found the smoke trail of an electrical fire on its galvanometer (galvo) control board. This board is cooked in a very literal sense. Even though the printer is long out of support, I contacted FormLabs hoping for a replacement board. While waiting for a response, I took the printer apart to get a closer look at the damaged board.

It looks far worse from this angle. A lot of charred and burnt plastic at the base of power connector, which had melted together into a single lump. It is no longer possible to (neatly) unplug this connector. A surface-mount capacitor C20 has been vaporized along with some of the circuit board creating a small pit.

Holding the board at a different angle, I saw charred residue of smoke trail running all the way up the board. This fire was more significant than I had previously thought. This is good news and bad news. I had been worried that I cooked the device with a nonstandard power supply but seeing extent of damage confirmed it happened before I got my hands on the device. If it happened on my watch, I would have definitely smelled dead electronics, a scent I was reminded of quite recently.

On the downside, severity of this damage puts repair out of reach of my current skill level. I don’t know anything about how galvanometer control circuits are supposed to work. My electronics engineering skills aren’t good enough to reverse engineer this board and fix it without technical information like schematics and diagnostics procedures.

After this (very discouraging) sight, FormLabs got back to me: no replacement galvo control boards are available. Unsurprising but at least it didn’t hurt to ask. I briefly considered buying a laser light show galvanometer setup from eBay or Amazon. But even if I could interface them, I don’t know how to test and tune them for good resin prints. Given these challenges, I’m not going to try to get this printer printing. I’ll focus on learning as much as I can from taking it (further) apart.

I had been given a FormLabs Form 1+ resin printer that’s been sitting unused for years and requested to get it back up and running. Working with FormLabs equipment isn’t cheap, and this “free as-is” printer required nearly $300 of stuff just so I could see if it even runs. With the hardware in hand, I moved on to the software side of things.

All FormLabs equipment require their PreForm software to run, and the current version (3.25.2 as of writing) no longer supports the Form 1+. I dug through FormLabs support to find this page Using PreForm with the Form 1+ which provides a link to download PreForm 2.20. That was the final release before PreForm dropped support for this old printer. PreForm 2.20 is also available for download from the page listing PreForm versions and their equipment compatibility. If someone wants to go even older because they have a need for 32-bit edition, PreForm 2.16.0 was the final 32-bit release and available on that same page.

Installing and launching PreForm activated an introduction to the software, which guides us through printing the FormLabs test object: a (hair?) clip in the shape of FormLabs butterfly logo. I followed through the tutorial to properly orient the shape and generate supports. I installed the Form 1+ compatible aftermarket resin vat from Z-Vat industries, and poured in Form 1+ compatible aftermarket resin from ApplyLabWork. I hit print and started hearing the buzzing of the Z-axis stepper motor. A good sign! Given the upside-down printing nature of resin printers, the metal printing platform blocked my view of what it was doing. I left the machine alone to do its thing.

Roughly half an hour later, the print height has risen enough I could see between the print platform and the vat. I had hoped to see a sturdy print raft forming the foundation of my test clip, but I saw only a lumpy misshapen blob. This is not good.

Watching the machine work, I could see the laser illuminated only a single spot instead of sweeping through the shape as I had expected. I didn’t see movement from the resin vat, either, which was supposed to move as part of peeling process between layers.

After I cancelled the print job, the build platform was raised to its maximum height where I can confirm the misshapen blob. This is definitely not the intended test clip object. It isn’t even in the right place. The test clip was supposed to be close to the peeling hinge edge. (Right side edge in picture above.)

The unmoving laser beam is what hardened the blob. It also hardened various bits of resin which are now floating amongst still-liquid resin. I drained all of that contaminated resin into a disposal container that I will leave out in direct sunlight to harden. Wiping the resin vat clean of residue, I see a hole burned in the precious PDMS layer.

The good news is that all the aftermarket hardware I bought for this printer worked: the aftermarket AC power supply brick seemed to deliver enough power, the aftermarket resin hardened in response to the laser, and the aftermarket resin vat’s PDMS layer allowed the hardened resin to separate between layers. That’s great! But there is something wrong with the printer itself and I’ll take it apart to look for hints.

This FormLabs Form 1+ resin printer was purchased as part of a company’s R&D project. Presumably sometime between June 2014 when Form 1+ was released, and September 2015 when Form 2 launched. It printed a few things and sat neglected since. Recently it came into my possession in “AS-IS” condition delivered by someone several steps removed from that R&D project. The people in that project has since departed, and all he knew was that “something was wrong with it”. If I could produce satisfactory results from this printer, they may subcontract me to print some parts for them and earn an operator’s fee to run this machine that used to be theirs. If I fail, they’ll still be happy because it’s no longer uselessly taking up space gathering dust at their facility.

When this agreement was reached, the machine still had a resin vat that held resin left from its last print. Neither vat nor resin would be any use after several years of neglect. That plus the high probability of making a sticky resin mess meant they were disposed instead of shipped. I was not given the power adapter, either. During the years it sat unused, it had been moved from one workbench to another and became separated from its original AC power adapter.

Fortunately, FormLabs had the foresight to clearly specify power requirements right next to the power socket. I have several 24V DC adapters on hand, but none as high as 2.5A. The best on hand is a 1.5A unit, which I bought for the Neato vacuum charging experiment. I put the correct size barrel connector (5.5mm OD, 2.1mm ID) on the wire and plugged it in.

That was enough for the printer to go through its startup sequence. Now assured the printer at least powers up, I will order a 24V power supply that can supply more than 2.5A. (*) What else would I need to run this printer? The Form 1 and Form 1+ have fallen out of official FormLabs support since March 2017, so now the best reference material I have is the “Retro Form 1 Guide” compiled by a user and posted to FormLabs user forums.

Another consequence of being out-of-support is that FormLabs no longer sells replacement resin vats for the 1 and 1+. These are considered consumables due to something called “PDMS layer” at the bottom of the vat. PDMS in this context may or may not mean polydimethylsiloxane, but I understand it is something that gradually degrades during printing so it (and the resin vat it is attached to) needs to be replaced periodically. With FormLabs no longer supplying this consumable, I looked for aftermarket solutions and found Z-Vat Industries. They would sell me a replacement resin vat.

FormLabs also no longer sells their specifically formulated resin in bottles we manually pour into a Form 1 resin vat, only in cartridges for installation into Form 2 and 3 which dispenses resin automatically as needed. From this FormLabs forum thread, I learned that resins for DLP resin printers are very different formulation from resins designed for laser resin printers like this Form 1+. (Quick summary: laser resin is designed to be sensitive to a quick flash of intense laser beam, DLP resin is tuned for longer exposure to less-intense light.) This fact drastically limited my options of aftermarket resins, leaving a few vendors like ApplyLabWork. Looking over their catalog, I will avoid the brittle precision resins and order one of their resilient “Robust” resin.

Resin printing is expensive, and FormLabs resin printing more so! I’ve spent nearly $300.00 just so I can find out if the printer even works. And the answer was… it doesn’t.

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(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.