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820-3481 iMac 2013 27" no external Display

D

Dozer

Member
device is working good but no external display possible, both ports I can connect the cable but monitor has "no signal"

dont found schematic and boardview but i took the 820-3299 seems to be similar.

L9400 and L9600 both sides have 3.3V

U9610 pin 19/20 3.3V

TBTA/BPWRSW_EN is 3.3V
TBT_S0_EN = 3.3V

TBT_A/B _HV_EN is 0V
R3688/87 is 10K

perhaps I have a problem with u3600?

R3695 has 806 ohm, on Pin 2 ans 1 is a nice clock with 25MHz


I am stucked now with this problem and would be glas about some help
 
D

Dozer

Member
yes, with an MBP 2011 15" working good

and the client told me the problem as well. he notified the problem when he wanted to connect another display in home office.
the machine came in to replace drive and check the connector problem
 
2informaticos

2informaticos

Administrator
Staff member
So the client complains that external video was good before replacing HDD?
Then check for knocked off components, or broken traces.
 
D

Dozer

Member
ok I will check that.
But the client did nothing. He only want to connect an external display and notified that it is not possible.
then he used the imac normaly until he decided to have a bigger drive. he bring the device to me for replacing and pleased me to have a look during replacing for the problem with the thunderbolt
 
2informaticos

2informaticos

Administrator
Staff member
So thunderbolt issue is older.
First, clean thunderbolt pins and corresponding area in the MLB.

Check TBT_A/B_HPD on the port where you connect the device.
 
D

Dozer

Member
I cleaned the thunderbolt pins and the corresponding area on both sides from the MLB

TBT_A/B_HPD when disconnected is 0V, if connceted is 3.24V but no display to see

I check only the mainboard with RAM and extern SSD and connected extern Display, nothing more connected
 
D

Dozer

Member
I found another, a real 820-3299. plugged in only with power and extern display cable I get a picture
 
D

Dozer

Member
Problem ist solved! thanks to @EsteTron, I found the same problem

iMac 27" Late 2013 820-3481

Got an iMac that thunderbolt is not working. Opened up iMac and discovered a noticeable burn in the thunderbolt IC U2800. The part number is DSL3510L and I have this same IC on a donor 820-3437 MBA L2013. My question is, is it even possible to replace the Thunderbolt IC, or is the firmware...
boards.rossmanngroup.com boards.rossmanngroup.com
after replacing the burned Thunderbolt Host working great again, thanks all for help
 
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