Powerboard (Siemens 11017800)

[Traceless]

Hi everyone,

I'm currently trying to repair the power board of a washing machine. Albeit there was no visible damage I found and replaced a defective diode (see picture below). Unfortunately this was not the only fault. I used my multi-meter to try and trace the problem (measurement see picture below, the blue and red arrows indicate the resistance between two points on the board). The readings seem to point towards the yellow path that runs through the DSC (dsPIC33EP256MC206).



To test the DSC I used its pin 41 (Vss) and found very low resistances between that and the following other pins (cf. dsPIC33EP256MC206)

Code: [Select]

Resistance | Pins
in Ohm     |
----------------------------------------
<= 0.01    | 5, 8, (9) 11, (20), (25), 50, 55
0.02       | 32
0.03       | 31
0.08       | 64
----------------------------------------

Solely based on the measurements I currently suspect the DSC chip to be the problem. However with a dead DSC I'd expect the washing machine to not run at all, yet it was still partially working.
In particular I could turn it on, select a program (time was correctly displayed), starting the machine would even start the pump. Once the target water level was reached though the program would not
proceed and the washing machine would sit idle indefinitely. So now I'm now left scratching my head, am I missing something?

--
Cheers

Traceless

[Traceless]

I have been thinking about the options available to me and how to proceed. I guess the easiest thing would be to get a replacement power board for ~160€ plus shipping. However I still don't really know why the old one failed. Maybe the broken diode was just marginal to begin with and when it died it also killed the PIC. However if something else is wrong the replacment power board might blow up in no time as well. Alternatively I could just desolder the PIC33 from the broken board and see if that fixes the problem. While it is not expensive to get a replacement PIC, getting the actual software is a lot harder. If the old chip is broken I can't get it off of that chip. I guess I could try the following:

• Order a replacement powerboard
• Get a PICKit4
• Use the PICKit4 to read the software from the PIC33 on the new board
• Get a blank replacement PIC33
• Flash it with the software from the newer board
• Repair the old board with the replacement chip

If I get the fault again then I still have the replacement board as backup and also always can replace fried PICs using my backup image as well. However I haven't worked with PICs in the past, so I am hoping to get some advice and/or an estimate if the above plan has any chance of success? In particular I see the following potential problems:

• PICs do feature some DRM measures (aka CodeGuard). I am not sure if I'm guaranteed to be able to read the software of the chip on the replacement board at all.
• The PICKit4 is advertised as an "In-Circuit-Debugger". Can I read software of the chip while it is still soldered to the replacement board or would I have to desolder it first? (soldering and desoldering TQFP is fiddly and there is some chance of damaging the chip so I'd prefer not to start soldering on the replacement board if possible.)

[ace1903]

Could you please post wider picture of the board together with IGBT bridge part number.
To me is unclear where damaged diode was connected? IS it part of 3,3v/5v  power rail or is it part of the high IGBT gate drive?
When IGBT bridge fails it is accompanied with rectifier failure and lot of smoke and holes in the ICs.
Low resistance reading looks OK since it is on low side current shunt path.
Guess that when target level is reached next step is to heat the water to chosen temperature, so it is good if you can check heater resistance , its driving circuit relay/triac and probably measurement sensor NTC/PTC placed on the drum.
 

[Traceless]

Hi ace1903,

thank you for the response. As requested I added some more pictures of the board (see below).

Regarding the low resistance readings, please note that on the two pads right above the C1603 label there was originally a 100nf smd cap installed. I took it off because both both pads are shorted to ground. Regarding the diode: one side of that diode is connected to the 0 Ohm resistor below L1601 as well as the 0 Ohm resistor next to "C8901/C8907" (I think this is visible pretty well on the picture "powerboard_top_002.jpg"). The other side seems to be connected to the 9th pin of IS2401 (counting starting from the top left side of IS2401 on image "powerboard_top_002.jpg").

Port X11-X3 connects the load- and unbalance sensor and uses 3.3V.

[ace1903]

On the board there are two switching supplies. First one is 3.3 or 5v for  dsPIC and second one 12 or 15v for the relays and this IGBT bridge for the motor.
My theory is that this 12v is dead and that is why relay for the heater is not actuated and motor does not spin. Check part number of the switching chip and see the datasheet.
Probably there is some fusible resistor that went open when diode shorted.

[Traceless]

Hi ace1903,

unfortunately neither IS2401 nor GR1400 are labeled. I already unsuccessfully tried to get schematics and/or a bill of materials for the board from the vendor - they won't hand them out. Especially IS2401 looks super custom - I already tried to find it, no luck so far. This is the first time I've seen a package like this. If anyone knows these parts (IS2401 and GR1400 on the pictures) I'd be grateful for any hints. So all I can currently rely on for debugging is the (defective) board itself which is not much.

[ace1903]

Read the label on the 7 pin chip next to GR1401. Check those two zero ohm resistors nearby the diode that you have replaced.
That diode I guess should be zener diode not rectifying one. That is why it is important to read the label on 7pin chips.

[Teichhermelin]

The IS2401 could be this one ...IS2401 IRAM535-1065AS
Take a look at this one ... TNY284 (7-pin IC)
If it doesn't work, it's also the end of the day.

[Traceless]

@ace1903:
Okay I checked the 7 pin chip, the label is quite faint it reads either LNK30406 or LNK304DG.

@Teichhermelin:
Wow, thanks for the hint I think you might be right - the IRAM535-1065AS looks very similar to the IS2401 on my board

[ace1903]

Schematics shown in LNK304 datasheet is very similar to the components present on the board.
Chip has no enable pin so 12v is always on. You can power the board outside the machine and check if 12v are there.

[perieanuo]

https://sw19.ru/forum/15788
maybe that iram is the one shorted? somebody reported after changing this one, it resolved the problem
if that's the case, you find plenty on ebay like this one https://www.ebay.com/itm/123465494982?hash=item1cbf1df1c6:g:~6oAAOSw-tlb3Fqd
but first, find the shorted device like others suggested, maybe on 12V rail

[Traceless]

Hi everyone,

I'm back with a few updates, first I added some parts numbers and pin numbering for IS2401 (suspected IRAM535-1065AS), for better clarity.



I desoldered Pins 7, 8, 9 of IS2401 (marked with a red rectangle in the above picture, the picture was taken before I desoldered thats why the joints are still visible). Afterwards I measured high resistances between Pins 7, 8, 9, A, B, C so IS2401 seems not to be shorted internally, for now I assume that it still works. I also measured resistances between all Pins on the LNK304DG, there was no dead short between any of them, also across both ES1J rectifiers next to the LNK304DG I measured high resistances. The short is still present and must be somewhere else on the board.

[Teichhermelin]

Sorry ... I meant this chip ... please have a look at it ...

[Traceless]

@Teichhermelin

I measured the chip you marked, it is labeled TNY285DG. In-between the pins on the "4-pin-side" I measured 0\$\Omega\$ as expected, both in-between the pins on the "3-pin-side" and across the IC from the "3-pin-side" to the "4-pin-side" I got readings in the 50k\$\Omega\$-1M\$\Omega\$ range. So I guess no short there either.

[perieanuo]

Schematics shown in LNK304 datasheet is very similar to the components present on the board.
Chip has no enable pin so 12v is always on. You can power the board outside the machine and check if 12v are there.

well, you gotta check those voltages, especially 12V
if you don't have that 12V for example (or the 5V or whatever), disconnect the ps that make that voltage and apply the voltage from external power supply.
you don't know what voltage to apply? well that's easy-peasy, that voltage is supply for some IC, read IC datasheet and you know what to apply.
or just start from 3.3V rising with current limit and raise current limit and see who's gettin hot on the board
all this take less than 1 hour, datasheet search included, reverse engineering included
maybe you have just a shorted cap, try to test with diode tester not with resistor tester, diode tester 'polarize' stronger the DUT

[Traceless]

Hey everyone,

thanks for the additional input. I made a short video today to summarize the problem. I haven't hooked up the board to a power source yet because I already know there is a short and did not want to risk frying the dsPIC. Of course, as I wrote in my first posts, there is a good chance that this chip is dead already (the reason you will see in the video). Anyhow I guess to see if there is still any life left in the dsPIC I could try and order some Micro IC clamps attach them to the dsPIC and try to power it with 3.3V directly. Alternatively I could do as I wrote in my second post above, get a picKIT4 and diagnose the chip with that.

Anyhow if you guys have better ideas let me know. I hope the video helps to clarify the situation a bit better.

[sperb]

I don't have information specifically about this board/micricontroller, but I think that is unlikely you be able to download/recover any firmware from the original microcontroller. The usual practice is to password protect the firmware. If the microcontroller is bad, unfortunatelly the board is trash.

[Traceless]

After putting the board aside for a while, simply because I didn't have the tools at hand to investigate this further I've now upgraded and decided start another attempt. It turns out that my initial assumption that the DSPIC might have shorted out was wrong. I took the chip off, as well as both IS1543 and TS1542 and the short is still present. Currently my attention is again on IS2401 which as suggested Teichhermelin might be an IRAM535-1065AS. Unfortunately I did not find any datasheet for that IC. I tried to find out as much as possible about how the chip is wired with the DMM. I marked the connections in the image below, green traces are connected to ground, red traces are non-ground connections between endpoints. What currently seems odd to me is that the three dedicated pins A, B, C, which lead to the resistor banks above L1601 are all short to ground as are the two pads for a (now removed) ceramic cap next to C1603 . Also the pads of pins 8 and 9 of IS2401 are shorted to ground, while the pins are not shorted inside IS2401 itself, the resistance between pin 8 and 9 is around 100k Ohm. So there seems to be sth. wrong. Does anyone know how those IRAM535-1065AS work? To me it seems odd that pins A, B, C are all connected to ground, but three distinct traces are routed to the resistor banks above L1601. Since the short shows up everywhere on the board but does not seem to be tied to any component I now wonder if the short is within the PCB itself.

[Traceless]

Just posting an update on the last picture. I'm currently trying to get a better understanding of what is going on around the 8-pin IC labeled "293 GZ606" next to those resistor banks that connect to the pins A, B, C on the IRAM535-1065AS.

[ace1903]

It is overcurrent detection. It allows IGBT bridge to be preventively turned off if voltage drop on sense resistors is greater than trip value.
All IRAM chip work on same principle. Look at some application note for motor control.