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820-2530 no chime no display but turns on.

stray77

stray77

New member
First post...
Like the title says, 820-2530-A, charges battery, shows power and charge leds, turns on with battery or charger alone, fan spins normally for the first few minutes then slowly speeds up to max rpm, cpu warms, video warms...however no chime, hence no display.
PP1V05=0.779V
R7780, R7781 both somehow measure 193K ohms but schematic says 7781 should be 806K ohms and 7780 should be 255K ohms (this has me confused)
PP3V3_S5=3.3V

PP18V5_G3H=16.93V
PPBUS_G3H=12.58V

The S3 rails look good but I didn't write down values, just checked them off with the exception of PPVTT_S3_DDR_BUF which I didn't check.
There doesn't appear to be any water damage, lvds connector looks good as well as the cable. I have no way to test the display independently however I have no reason to suspect it being bad.
I would love some guidance...

The only spare parts I have on hand are from several other branded laptops, otherwise I'll be looking to your suggestions for replacement parts, lacking that, it would be ebay.


p.s. I enjoy the live streams but I'm not getting notified until long after they are over.

http://imgur.com/K3y4PtI
http://imgur.com/HeHSuRW
 

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dukefawks

Administrator
Do you have a programmer to flash the ROM chip? Is there any history on this board, they usually don't just fail like this.
 
stray77

stray77

New member
unfortunately there's no backstory. It's owned by a cute waitress at the corner bar, she brought it to a "few" places, all said they couldn't fix it (no specifics given). Again, no signs of water damage or corrosion or any signs of anything but normal wear and tear. There were a couple screws missing but just from the bottom plate. I have a raspberry pi 3, arduino, ftdi, and USBASP + ISP 51 for Atmel AVR USB Programmer ..if one of these will do, ill happily try to reflash the bios. I thought I saw something about using a raspberry pi to flash the chip but have no experience with mac's.

Also, I edited my first post to include links to full sized images on imgur. I can't seem to delete the one remaining tiny image posted originally.

Looking at
SSTSST25VF032B4096SPIOKOKOKOK2.7003.600

it appears my raspberry pi will/should work based on
https://www.rossmanngroup.com/board...ite-erase-apple-efi-spi-rom-with-raspberry-pi
&
https://www.flashrom.org/Supported_hardware#Supported_flash_chips

I assume my 220 ohm resistors will suffice as a suitable substitute for 150 ohm in this use case.
http://imgur.com/EAXwlfw

If you think this is the path to take, I'll give it a shot.
 
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stray77

stray77

New member
I first attempted to reprogram the chip onboard and had no success, so I removed it and was able to read, erase and reprogram with file linked above. Unfortunately there is still no change in behavior. Anything else come to mind? Its so frustrating having a machine with power and charge leds, fan spin, harddrive spinning up, cdrom seeking and now a known good bios, but no chime or display.
 
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dukefawks

Administrator
At this point it could be anything. Is there any history on this board, they usually don't "just" fail like this.
 
larossmann

larossmann

Administrator
Staff member
My experience with this is bad MCP79 or corrosion from some light liquid that got under it. I'd just reflow it and see if it works. Do keep in mind that even if the chip is bad the replacements you will get are actually shittier than your reflowed zombie chip. I've reflowed a bunch that worked, and only a few worked when I replaced the reflowed chip with the "new" chip. I put the original "reflowed" one back on and it worked.

I am not saying this is something I would charge a customer for, but if you are at your wits end and just want curiosity answered, I'd reflow MCP79.
 
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