Bosch dishwasher controller without signs of life

[roli]

Hi!
At home we have an older Bosch dishwasher (SGV59A23/22) that suddenly stopped working mid cycle. The symptoms are... it's dead  . Pressing the power switch does nothing, the little LED display is dead, the program select buttons do nothing, ... Now I have traced the input voltage and that seems to be going in the right places. So the obvious culprit seems to be the actual controller board. This gets the mains voltage input (it does get there) and then has what I think is a simple switcher PSU on there that supplies the control circuitry.

When I first got the board in my hands I immediately noticed a cracked solder joint on one of the relays and a few more that look slightly dull. I re-flowed the most suspicious looking ones and tried the board again... no change.

So I took the board out again and started looking into it a bit more. There is a ST 78m05a voltage regulator (5V output) on there and it seems to be relatively near the PSU, so I assume that this is the main regulator. I tried applying around 8V to the input, just enough for it to start regulating - and it did. I was getting 5V on the output and the board was drawing around 500mA. That's when I noticed that the main MCU (mc68hc908ab32) was getting extremely hot - in just a few seconds really.

That's when I unplugged it and started doing some basic continuity checks and noticed that the regulator output and GND seem to be nearly shorted. There is about 16 ohms of resistance between those. Not sure if that is to be expected or not. Seeing how I was getting 5V on the output I am assuming that this is not an issue. What I am assuming is an issue is the MCU getting really hot. Could be that there is a short somewhere in the main MCU, or is it more likely that the short is somewhere external and that is causing the MCU to get hot? Do I even check around, or just assume that the MCU is dead?

Here are two pictures of the controller board. Sadly I cannot seem to find any schematics or anything, and I cannot find any replacements either.

[fzabkar]

I think it's clear that the MCU is dead and the PCB is a write-off.

https://www.nxp.com/docs/en/data-sheet/MC68HC908AB32.pdf

The CPU08 can address 64K-bytes of memory space. The memory map, shown in Figure 2-1, includes:

• 32,256 bytes of user FLASH memory
• 512 bytes of EEPROM
• 1024 bytes of random-access memory (RAM)
• 48 bytes of user-defined vectors
• 307 bytes of monitor ROM

VDD supply current

Run -   30mA
Wait -  12mA

[roli]

That was my fear, yes. I was just hoping that there might be some external factors that could possibly cause the MCU to start heating up as crazy.

[evac]

This seems to be Bosch part number 00488200, which appears to have some equivalent part numbers for Siemens/Neff models, google shows some online stores selling the part.

[DavidAlfa]

Check C2 and R32.
The TNY IC is a common failure too.

[roli]

This seems to be Bosch part number 00488200, which appears to have some equivalent part numbers for Siemens/Neff models, google shows some online stores selling the part.
(Attachment Link)

I was looking, but sadly I couldn't find anyone with the controller in stock. And even on some places that had it "out of stock" it was like 200€.

Check C2 and R32.
The TNY IC is a common failure too.

But since for my testing I hooked the power input directly to the voltage regulator (and also tried feeding 5V on the output) then those shouldn't really matter since I essentially bypassed those parts.

Anyways... new dishwasher has been ordered. This thing is at this point around 20 years old and has has recently had some random plastic part fail once a year. I think at this point it's better to just stop wasting time and money on repairs.