820-00875-a - a1708 - frying SSD'S

2informaticos

Administrator
Staff member
First, check diode mode to ground at 3V3_S4.
If good, check U8210 voltages; pins 1, 3, 4.
Do you get 5V_S0?
 

Anterweb

Member
Diode mode to ground at 3v3_s4 0.429

U8210 pin voltages 0v

and I get no 5v_SO

But when looking at the u8210 under the scope I spot this,,,

u8210_new.jpg
c8199 appears to be loose on the board.

I will solder this back and retest

Also I dont seem to have a pin 1 on u8210 in my board view?
 

2informaticos

Administrator
Staff member
Do you get L7670 voltage at least?
If yes, check output voltages from pages 59/61/62.

Remember to check in the 10s when you nothe the trackpad click feedback.
 

Anterweb

Member
Brill thanks dude, I'll check these when I'm back,
Could you just clarify what you mean by "in the 10s" I'm not familiar with this term?
 

Anterweb

Member
I don't, I posted a couple of days back that I get 0v on L7210/20 as I probe these the meter shows around 2.0v the instantly drops to 0v
 

2informaticos

Administrator
Staff member
"L7210 and L7220 both Start at 1.5v then instantly drop to 0.0v"
Tell us what is actual situation; 1.5V, 2.0V, 0V...
In the 10 seconds when you note the trackpad feedback is the moment to check for voltage on the board.
 

Anterweb

Member
I have been offered a logic board to replace this one but it he has said it has an EFI lock, Is this something I can get around on this model if I purchase the logic board?
 

Anterweb

Member
can I just swap the bios/efi chip on the boards when it arrives, new logic board is a 2017 and this current one is. 2016?
 

2informaticos

Administrator
Staff member
That can cause weird problems in time.
Need to clean ME region in BIOS, if use the chip from other board.
 

Anterweb

Member
I have decided to leave the old bios chip on its logic board as I still may be able to get it back to life some day,

So I need a new bios chip for the board arriving tomorrow , I can buy a pre programmed one from Ebay for £10 for this logic board or would you recommend I purchase the hardware required to flash it myself. This is something I have never done before but with the amount of mac repairs I am now receiving I think it is something I should learn and after looking into it last night it does not appear to be something outside of my skillset with the right advice.
My only concerns are what hardware to buy and where to find the needed bios files,
any advice on this much appreciated.
 

2informaticos

Administrator
Staff member
Medusa is most recommended for Apple stuff.
There are also other dedicated programmers available on Internet, with some kind of flex to connect directly to the logic board (J6100).
If you desolder/resolder the BIOS chip, then cheaper programmer (like CH341A, TLL866, EZP2019) may be used.

When you need a BIOS dump, just ask on the forum...
 

Anterweb

Member
So my programmer arrived today,

12-2.jpg 11-22.jpg
it looks like I can solder the chip directly onto the back of the programmer ( See pic ) but i'm also reading that its 3v direct from programmer then I have an adaptor (in pic 1 ) that looks like its a 1.8v. so I'm not sure what to put the chip onto at this point,

I have had a play with the software using an old winbond chip from an old laptop and it seems easy enough to read, wipe and re programme.

I just now need a clean bios file dump to use with the clean ME religion you mentioned before.
 
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