(347) 552-2258 [email protected]

A1708 820-00840-A no power

H

hgoncalves

Active member
Hi,

I have an A1708 820-00840-A with only 5V on ampmeter.

UPC_XB_SPI_CLK has only 0.120 on diode reading, and comparing it with other board, it seams to be low.

Should I replace U3200?

Can you help?
 
H

hgoncalves

Active member
It was on TBT_X_SPI_CLK, and after replacing U2890 the diode readiing on TBT_X_SPI_CLK went back yo 0.605, and UPC_XB_SPI_CLK to 0.669.

UPC_XB_SPI_MISO went to 0.055 on diode reading. Can U2890 be bad? How can i be sure?
 
Last edited:
H

hgoncalves

Active member
Replaced U2890 again, and now UPC_XB_SPI_MISO went back to 0.650 on diode reading, but still 5V only on ampmeter.
 
Last edited:
H

hgoncalves

Active member
It was R3205. It was 0.505 on diode reading, and it should be 0.740. After replaced it, it started to go to 20V, but only one time.

Now it is with 5V again...

Any idea?
 
Last edited:
H

hgoncalves

Active member
Client said it closed it one night, and in the morning it didn't start again.

However, it had oxidation signs on the backlight area, and client said it was two years ago, and it was repaired then (can't see nothing shorted there, except some caps a bit darker, but with normal diode readings).

Now, I've replaced U2890 for 3 times, and they only work on the first power on. Something is killing U2890, but I can't understand what it is.

Any idea?
 
2informaticos

2informaticos

Administrator
Staff member
Impossible to kill TBT ROM, if its power is correct.
Be sure adjacent resistors have good ohm value.
U2800 may have accumulated crap underneath, or internal problems; it connects with U2890 too.
Try to reball/replace it.
 
You must log in or register to reply here.
Top