mk4 mca radio schematic diagram need

[marekrbk]

the upper part of the main board is missing pin 4 from the top left. it probably leads inside the board. can you advise me if it is repairable?
the radio does not turn on, the screen is black and the consumption is 0.25mA.the memory is probably bad quality, but I can't read it because I'm missing the pin
https://de.aliexpress.com/item/32827909 ... pt=glo2deu

could there be a problem in the flash memory? I will try heating it to 400 degrees

[marekrbk]

I found out that Samsung has a similar memory K4H510838 we'll see if it helps....
edited: always dark

[Go4IT]

If you heat the flash tp 400 degree it will be dead. Anyhow, that don't make sense.
Before you rip off the RAMs, have you tried if the chips react on heat?
Defective Rams in MCA is very seldom, as this problem disappears after NX series.
Now it's hard to tell if the replacement chips (did you only change one?) are fail or your soldering is bad.

[marekrbk]

the radio runs out of battery, I decided to replace the memory.. it lost connection with converse+ a couple of times. The soldering was fine, but the radio remained dark. I ordered more memory, I'm continuing my research.
Without a scheme, we will not arrive at a normal result because it is necessary to perform control measurements on the electronic board.

[Go4IT]

Be very carefull with further (de)solderings, as more pads would loose up,e even those with usage, not only unused ones.
A schematic won't help you much, as even with a scope, the signals won't make much sense. But you should check the powersupply of the RAM (pin 1, lower leftmost pin).
The Samsung RAM should would, so you may need to change the lower one also (make heatup-test first). The next thing would be to JTAG the firmware.

[marekrbk]

I tried the whole set of 10 pieces of memory, not one of them worked, now I'm waiting for the Polish memory, I'm curious about the result. I know how to hack, so it's not a problem, I also repair other hardware, I don't understand why the mca failed...https://www.youtube.com/watch?v=tc894qs01SE
so far, I have always put what I had at hand in working condition. If there was a scheme, it would have been running a long time ago

[uscovu]

Hi, maybe your problem is not there.... I remember, once I have fixed a very similar defect and the problem was on the board with buttons. There is an ntc and if this part gives wrong info to cpu it will not start. Search for liquid damage on buttons board. Very often, when people clean their audio units/nav system they pray cleaning solution onto display and that solution it will go inside the unit from the bottom of the lcd and damage some traces on pcb. Hope this will help you.

[marekrbk]

I'm going to look at the front panel. memories arrived from Poland and the same result

[marekrbk]

The next thing would be to JTAG the firmware.
[/quote]
Go4IT
what could happen to the firmware? my radio consumption is 0.28 ampere
what else do you recommend to watch?

[Go4IT]

The board is able to start even without the keyboard/display attached. If so, the powerdraw rises from about 220 mA (12V) up to about 650 mA. If not, something is wrong. Well, you already proofed more than enough that the RAMs are not the problem, even if you know that all kinds of Micron RAMs you buy these days are fakes and cheap replicas. In best you get relabled ones that are somehow compatible.

Next is to measure the small voltage regulator, ensure you measure the voltages right after applying the main power:

IMG_3595.JPG

Also check the power monitoring device:

IMG_3609.JPG

Then you should attach a Segger J-Link and follow the reflash-procedure after making a backup of the flash content to disk. You can just the attached firmware to program, just to see if that makes any difference in boot behaviour.

If so, try to attach the front-part, powerup and login with pin attached to firmware-zip filename. If that all works, use https://mk4-wiki.denkdose.de/artikel/na ... a_copy_pin to copy and flash the id-sector #507 from you backuped firmware back to the device and reassemble everything and make a standard update to realign everything.