Power up your board safely when you're unsure of your soldering skills - Page 1
Forum section: electronics / beginners

author: amateur_25
author_rank: Regular Contributor
timestamp: December 03, 2016, 08:26:26 pm
content: HiI accidently shorted out the thermistor on my 3d printer whilest removing the blocked noozle.I believe it has destroyed the controller board. No longer boots no matter what.Following dave's video on chipquik and smd solder. I've successfully replaced the part I think.I have done a visual inspection, I can't see any shorts but there could be a really tiny solder whisker there ready to ruin my expensive micro.It's my first 100 pin TQFP package and it costs 10 quid a pop (mega2560)!!!Is there a way I can power it up safely without it blowing up if i goofed up somewhere.Would current limiting help but I don't have a proper bench supply.

author: Simon
author_rank: Unknown
timestamp: December 03, 2016, 08:28:21 pm
content: Current limiting is all you can do but if you are under the correct voltage for the uC to work it sort of defeats the object but with a try.

author: Rerouter
author_rank: Super Contributor
timestamp: December 03, 2016, 08:57:57 pm
content: shorting the thermistor at the nozzle side will do no damage to the project 3d printer controllers,What is unclear is what you where soldering, and that you where soldering with everything unplugged or not, if it was powered while you where soldering, then that could have killed it,same for getting back in and triple checking that you dont have a tiny solder ball resting between 2 smd chips or similar,In such cases i go outside with the board, drink a drink, eat a snack, and look at it with fresh eyes, 9/10 times i catch the mystery short,

author: klunkerbus
author_rank: Unknown
timestamp: December 03, 2016, 09:37:49 pm
content: I agree with rerouter that a shorted thermistor shouldn't have damaged anything. Unless this printer has a very unique design approach, the thermistor is used in a simple voltage divider. With the typical NTC-type thermistors used on 3d printers, a shorted thermistor will cause the firmware to read a lower temperature than normal. Depending on the firmware configuration, you may even get a "low temp" error.One common way that the electronics boards *can* be fried is by 12V or 24V being applied to the thermistor wiring. This often happens when there is a failure in the hot end heater or heater wiring that applies heater power to the hot end aluminum block, and thermistor leads weren't properly insulated from the aluminum block.

author: amateur_25
author_rank: Regular Contributor
timestamp: December 03, 2016, 11:16:29 pm
content: I don't have a schematic as the ramps boards am using is believed to be a clone of clone.I put a pair vice grips across the thermistor by accident when I was trying to get some grip on the hotend.It's definitely blown the adc pin though because instead of showing 5v it was showing 1.8v on my scope.A blown adc pin no big deal as long as the other s work but the chip is some how locked up.The original marlin firmware didn't boot i.e. nothing on lcd or serial terminalI uploaded a basic flash led(arduino example sketch) and on the scope it just shown 5v i.e. no switchingThe serial stk500 bootloader wouldn't respond despite my efforts of re-flashing it on via the icsp header.But I could upload to it successfully using my avrisp mkII.Btw since I don't have any means to limit the current to 20ma, I just went for broke.IT's ALIVE!!!Code:startecho:Marlin 1.1.0-RC6echo: Last Updated: 2016-04-24 12:00 | Author: THE_KILLERCompiled: Dec 3 2016echo: Free Memory: 3321 PlannerBufferBytes: 1232echo:Hardcoded Default Settings Loadedecho:Steps per unit:echo: M92 X80.00 Y80.00 Z398.27 E94.50echo:Maximum feedrates (mm/s):echo: M203 X500.00 Y500.00 Z5.00 E25.00echo:Maximum Acceleration (mm/s2):echo: M201 X9000 Y9000 Z100 E10000echo:Accelerations: P=printing, R=retract and T=travelecho: M204 P3000.00 R3000.00 T1500.00echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s), Z=maximum Z jerk (mm/s), E=maximum E jerk (mm/s)echo: M205 S0.00 T0.00 B20000 X20.00 Z0.40 E5.00echo:Home offset (mm):echo: M206 X0.00 Y0.00 Z0.00echo:Material heatup parameters:echo: M145 S0 H180 B70 F0echo: M145 S1 H240 B110 F0echo:PID settings:echo: M301 P63.00 I2.25 D440.00 C100.00 L20echo:Filament settings: Disabledecho: M200 D3.00echo: M200 D0echo:Z-Probe Offset (mm):echo: M851 Z0.00

author: Rerouter
author_rank: Super Contributor
timestamp: December 04, 2016, 02:12:55 am
content: so does this mean it was just corrupted code, or is the pin actually damaged, if its an ADC input, i dont see why measuring 1.8V would be odd?