please help! ic20 getting hot! SOLVED!!!

[tupinamba]

Hi,
Values are correct.
Resistance between ground and pin 4 of USB chip is 9.9K.
Only 1 pin of USN jack gets 5V...

[guest]

can you power it all up again
and measure the voltage
on both sides of r9
there is something not right there
and it might be that your usb chip is fried

[guest]

also when done
turn power off again
and measure the resitance betweens pin4 and pin5
and from pin5 pin7 and pin8 to ground

[tupinamba]

Hi,
Sorry for the late reply, I was away for the week-end.

Voltage on both sides of R9 is around 0.24V when only the power supply is plugged in. Then it's 0.82 / 5.04 (USB plug side) when USB is plugged in.Then it's 3.48 / 5.04 when both power supply and USB are plugged.

Resistance between pins 4 and 5 seems to be bove 2M (my multimeter doesn't show above)
It's the same between ground and pins 5, 7 and 8...

Thank you for your help, I do really appreciate !

[guest]

turn off power
and measure resistance
from the r9/r10 juncture to pin4 of the usb chip
it should be 0ohms

your previous measurements showed .24V on pin4
and now you have 3.48v on r9/r10 juncture
so there may be a bad solder joint somewhere
or a broken trace

[tupinamba]

Hi,

Resistance btw R9/R10 juncture and pin 4 of USB chip is 0 ohms.

Just to be clear :
Voltage is 0.24V on pin 4 when Power Supply is connected
Voltage is around 0.8V on pin 4 when USB is connected
Voltage is 3.48V on pin 4 when both Power Supply and USB are connected.

Is this weird ?

I've been looking for bad joints or broken traces but haven't found anything...

[guest]

were your usb chip voltage readings
done with both usb plugged in and power on
if not
can you redo those

its starting to look like a bum chip

[tupinamba]

Yes, the readings were made with both USB and power supply plugged in.
You think it's the USB chip ?
Could this explain why I get 0V on pin 1 of jumper 3 on the I/O board instead of the expected 0.18 to 0.24V ?

[guest]

the readings you have for pin4
seemed to have changed then

can you measure the resistance to ground
for every pin on the usb chip
after looking at the votlages you gave before
there is definitely something wrong near pin10
just report back any of the shorts

[tupinamba]

I measured the resistance of every USB pin, with power and USB plugged in.
Everything is above 2megs except for :
pin 5 (2.5k)
pin 7 (3.8k)
pin8 (17.8k)
pin 9 (0.07k)
pin 17 (0.03k)
pin 32 (0.03k)

[guest]

im not sure exactly whats going on
it could be a bad chip
and that might be the easiest place to start for now

[tupinamba]

Could a bad USB chip be the reason why I get 0v on pin 1 of jumper 3 (I/O board) instead of the expected 0.18-0.24v?
Could the chip be burnt because I first put IC4 the wrong way on the mainboard?

[guest]

reversing ic4 shouldnt hurt the usb chip
and a bad usb chip
would give wrong readings on pin1 and pin2 of j3

although it still could be a short someplace
can you retake all the usb voltages
with the power and usb cable plugged into the computer
your first set has different readings than you gave me later
and id be curious to see if any of the other readings changed

[tupinamba]

Here are the new readings with both USB abd power supply connected (the first readings were made with only power supply connected):

pin / normal voltage // my values
1 / 0 // 4.64
2 / 5 // 5
3 / 5 // 5
4 / 3.3 // 3.48
5 / 3.3 w. data // 0.01
6 / 3.3 // 3.46
7 / 3.3 w. data // 0.01
8 / 0 w. data // 0.01
9 / 0 // 0
10 / 5 // 0
11 / 0 // 0
12 / 0 // 0
13 / 5 // 5
14 / 5 // 5
15 / 5 // 0
16 / 0 // 0
17 / 0 // 0
18 / 5 // 4.62
19 / 5 // 4.62
20 / 5 // 4.62
21 / 0 //0.07
22 / 5 // 4.62
23 / 5 // 0.28
24 / 5 // 4.63
25 / 5 // 0.46
26 / 5 // 5
27 / clock // 1.64
28 / clock // 2.37
29 / 0 // 0
30 / 5 // 4.8
31 / 0 // 0
32 / 0 // 4.62

The main changes are on pins 4, 23, 25.
On pins 10, 11, 12, 15, 16, voltage is now 0v instead of 0.07 or 0.01.

[guest]

ok tihs is the last thing i can think of
turn off power
and measure resistance from pin2 of usb jack to pin8 of usb chip
and from pin3 of usb jack to pin7 of usb chip
if youre not sure which pin is which on the jack
just measure from both middle ones
and report the lower resistance value

also
have you tried the usb cable with something else
just to verify its not the cable