Joined: 24 Jun 2010
|Posted: Thu Jun 24, 2010 15:33 Post subject: wrt150n hardware BUG
|I discovered a hardware bug today.
After searching to web, I found out that almost all wrt150n v1, v1.1 have this problem.
red circle from top to bottom:
1. label shows its a 1.8v test point
2. but the measurement shows 2.2v
3. it is a lm117-3.3v compatible ic
4. the input is already 3.3v
5. the resistors are 50ohm and 100ohm
The 2.2v is generated because the Vdo of lm117 is just about 1.1v.
So 3.3v - 1.1v = 2.2v.
According to the label(1.) and the resistors' arrangement it is logical to conclude that the lm117-3.3v is mistakenly used to replace the lm117-adj.
Although it might be because the broad really needs 2.2v to operate, this is a very bad voltage regulating solution.
While the Vdo is not achieved,lm117 will not actually regulate to volatge at all.
I guess this IC is powering the BCM5325 because it is right becide it.
To support my assumption, I teared apart a few other routers/switches that has a Bcm5352.
All of them has a 1.8v regulator beside Bcm5352.
1. ignore it for the router has no relibility problem all this time.^.<
2. replace the lm117-3.3 with a lm117-adj
3. replace the lm117-3.3 with a REGULATED 2.2v
Please tell me what you think, I would really appreciated. Thank you