Duet Wifi heats Bed and Hotend from start

sixfeetunder · 26 Oct 2018, 08:59

Hello, since yesterday my Duet Wifi starts heating up instant after startup. The Webinterface, home all, sensor readings... Everything works like before. Just the heating cant be "controlled". I installed a new fan about one day before the problems, but i cant see a connection between these two events, as the fan worked like intended. I add some Photos of the cabling and the heating LEDs, so you see what i mean.
Thanks in advance!

Jacotheron · 26 Oct 2018, 10:22

Usually this is a case of failed mosfets. Mosfets are the digital switches being used to control the heater outputs, but in stead of mechanical separation, like a relay, mosfets are solid state. Since they are solid state, they can fail in a "closed" position - allowing power to run through.

They can fail for various reasons, but usually it is a short - I have also heard of cases where they simply went bad for no apparent reason.

Mosfets have 3 pins, though for the ones used here, there are 2 pins and then their back. You can carefully measure voltage between them to determine if they are working well - on your photo they are the 2 back chips towards the bottom right (near the LEDs) and the one that looks the same near the heatbed output. On your photo I can see all of them have their LEDs on, so at the time the photo was taken, all of them are on (if not commanded, they are probably blown).

sixfeetunder · 26 Oct 2018, 11:15

Wow that was a really good explanation. thanks for this.
The LEDs are in this (on) state as soon as i Power on and in the webinterface they are commanded as "off". So i guess they are blown for whatever reason?
is there a way to fix this?

edit: i have 2 external Mosfets built in, does this help?

dc42 · 26 Oct 2018, 11:25

If both the hot end LEDs and the bed LED light up uncommanded, then it's unlikely that all 3 mosfets have failed. More likely is that the 74HCT02 driver chip (U11) has failed. The most likely cause of that would be a short between +5V and VIN.

Jacotheron · 26 Oct 2018, 11:28

I also thought it is strange that all 3 failed at the same time. Normally mosfets only fail one at a time.

sixfeetunder · 26 Oct 2018, 11:37

thanks for your response. this sounds Not that good. is it possible to teplace this Chip? it would be a shame to throw that nice piece of Hardware into trash because of one 1-Dollar Chip right?

T3P3Tony · 26 Oct 2018, 11:59

@sixfeetunder where are you located? User @W3DRK is in the US and does repairs. Does the board work other than the MOSFETs? VIN to 5V circuit might have caused some.other damage.

sixfeetunder · 26 Oct 2018, 12:02

i am located in germany, at the Moment i dont see any other Problems. Motors and Sensors are working so far

T3P3Tony · 26 Oct 2018, 12:37

@sixfeetunder Do you have the capability to replace a SMT component or know of someone.local who does. It may just be U11 that needs replacing

Jacotheron · 26 Oct 2018, 12:38

Looking at my DuetWifi v1.03 board, U11 is a small chip close to the 2 extruder mosfets^ (near the USB port; on your photo slightly hidden behind the blue and black wire's connector [looks like temperature input connector]). I have soldered this size chip before (I have limited soldering experience, I would say novice level), and here is my recommendation:

If you have access to a hot-air station, that will help you a lot.
Use a small tipped solder iron.
Use a good amount of flux while desoldering and soldering (the flux can help to keep the pins separate).
Be careful for making it too hot (especially the new chip).
Before you start ensure you make a note or mark of the chip's orientation (there may be a mark in the silkscreen, always better to be safe than sorry).
The C54 capacitor is in very close proximity to the chip, be careful around it.

If you don't feel confident doing this, rather get a friend to help, or maybe ask a repair center to help you with this.

^ On mine, this chip in U11 is marked as "HT02 78KG4 A7H8"; U12 (in the corner near the wifi module) is marked as "HC74 73KG4 ..." (bottom line is not very clear);

sixfeetunder · 26 Oct 2018, 14:51

theae are my Chips. i guess i should get a and try to replace it or find someone who can help me with this?
should i buy exactly the Model which is written on the Chip? HT0278KG4 A7H9

dc42 · 26 Oct 2018, 14:57

You need a 74HCT02 chip in a TSSOP package. A typical part number is 74HCT02PW or SN74HCT02PW. The PW suffix is the package type.

sixfeetunder · 27 Oct 2018, 08:14

ok i get some of these. Thanks a lot for you help

sixfeetunder · 31 Oct 2018, 20:38

So now i switched the chip and i think i did a quite bad job, but it should work. at least from my point of view. The board is still working (can connect to it with yat and the heat LEDs are not flashing from start). so far so good. but now i have another problem: when i start the board and want connect to wifi, the wifi module is blinking blue and then switches off. in yat i get following message:

M552 S1
ok<LF>Error retrieving WiFi status message: SPI timeout<LF>WiFi module is idle<LF>Error retrieving WiFi status message: SPI timeout<LF>Error retrieving WiFi status message: SPI timeout<LF>Error retrieving WiFi status message: SPI timeout<LF>Error retrieving WiFi status message: SPI timeout<LF>Error retrieving WiFi status message: SPI timeout<LF>WiFi module is idle<LF>

Do anyone have an idea what i could have damaged or what is wrong? maybe i forgot something?

SupraGuy · 31 Oct 2018, 22:04

No expert here, but does your board remember your network?

Is the M587 command still in your config.g?

M587 S"WiFiForSupraGuy" P"SupraGuysSuperSecurePassword"

You can enter just

M587

using your terminal, and it should tell you what networks it remembers. I generally start wifi troubleshooting with purging all of those, and adding them again.

You could purge all networks with:

M588 S"*"

Or just specify the networks you want to forget.

dc42 · 31 Oct 2018, 22:19

@sixfeetunder said in Duet Wifi heats Bed and Hotend from start:

So now i switched the chip and i think i did a quite bad job, but it should work. at least from my point of view. The board is still working (can connect to it with yat and the heat LEDs are not flashing from start). so far so good. but now i have another problem: when i start the board and want connect to wifi, the wifi module is blinking blue and then switches off. in yat i get following message:

M552 S1
ok<LF>Error retrieving WiFi status message: SPI timeout<LF>WiFi module is idle<LF>Error retrieving WiFi status message: SPI timeout<LF>Error retrieving WiFi status message: SPI timeout<LF>Error retrieving WiFi status message: SPI timeout<LF>Error retrieving WiFi status message: SPI timeout<LF>Error retrieving WiFi status message: SPI timeout<LF>WiFi module is idle<LF>

Do anyone have an idea what i could have damaged or what is wrong? maybe i forgot something?

Try re-installing DuetWiFiServer.bin. If it is already on the SD card, you can do this by sending M997 S1.

sixfeetunder · 1 Nov 2018, 01:59

@SupraGuy
i tried that already, but thanks for your help

@dc42 said in Duet Wifi heats Bed and Hotend from start:

M997 S1

i placed DuetWiFiServer-1.21.bin on the sd card and tried your command. But i guess it doesnt work as expected. This is what i get back:

M997 S1
Trying to connect at 230400 baud: failed<LF>Trying to connect at 115200 baud: failed<LF>Trying to connect at 74880 baud: failed<LF>Trying to connect at 9600 baud: failed<LF>Error: Installation failed due to comm write error<LF>ok<LF>

thanks for the fast reply

edit: i tried it in root and in sys directory

Phaedrux · 1 Nov 2018, 01:59

@sixfeetunder I think the file has to be named exactly DuetWiFiServer.bin

sixfeetunder · 1 Nov 2018, 07:40

Thanks for the hint. i renamed it and recognized that there was already a file like this in the sys folder. i replaced it anyways with the new one but i get the same result "installation failed..."

Jacotheron · 1 Nov 2018, 07:44

The Baud Rate is the data rate at which the main processor communicates with the Wifi chip, using the UART / Serial protocol.

The fact that it fails to get any response, tells me there is an issue where a trace between the 2 may have an issue.

The UART communication uses 2 data lines: TX (transmit) and RX (receive); the TX of one goes to the RX of the other. If a data line is damaged, the communication will fail.

One of the other guys might be able to tell you where to look for these traces.