Sun Blizzard A/C Machine QTech II - troubleshooting board and cpu

[DK87]

Hi there,


a few days ago I obtained an A/C servicing machine for cars/trucks.

It's in rather nice condition, but has one major issue: the LCD isn't showing anything. (see attachment)

So I began to remove the board along with the lcd to test it on the bench.

I took an visual inspection and I found an corroded ic  (but seems to work just fine...I had probed it later)

Then I probed the connections comming out of the board to the LCD and there is no valid signal comming out of it:

frameground, ground, backlight positive and backlight ground are working
pin 6 (Read Select :->5V 140Khz square wave signal.... seems to be okay?
pin 11 (DATABUS 0) -> 3V 70 Khz sqare wave signal   hmm...
All other lines are DEAD 

So I think the problem is not the LCD.

I digged further and tried to get a connection to the LPC2148, but nothing works.

I probed UART0 Pins of cpu ->no valid signal
I probed UART1 Pins of cpu ->no valid signal

I tried usb-connection: error, windows says the device doesn't work.

Even if I pull the RESET pin low, and pin 0.14, so that the cpu will start the bootloader..no connections

I checked power supplies: 12V ok, 5V ok, 3.3 V ok.




I suspect the cpu hangs, has corrupted user software or is just faulty. 


So, can you help me further?
Do I have missed something?



Btw I noticed:
There are HCT573 octale D-Type latches.
On a few latches the LE (LatchEnable)  pin is on the 5V rail. Why?
I thought especially the latches which are connected to the lcd take the LE signal to send the databits simultaneouslyto to the lcd?


Unfortunately, I have no service manual or anything about that machine.
I contacted the manufacturer SUN aka Snap-On but still no answer.


Detailed and annotated pictures of the pcb are on my onedrive accout:
https://1drv.ms/f/s!AjDFITipILdAyUSNivWeN7ldm3ej


Thank you!

[Turhabi]

Hallo mein Freund ich habe gleiche Fehler wie bei die mit meinem klimagerät kannst du mir helfen hast du repariert was war den fehler bitte um Rückmeldung?
Liebe Grüße

[ebastler]

DK87, the original poster, has last been seen on this forum in 2019. (You can click his user name in the post above to see that.) So it is unlikely that he will respond. Also, please note that this forum uses English language.