820-01041 5v ub400 getting hot

Donlan78

Member
working on a1990 that was working but had failed usb port, replaced the bad cd3215 (ub300) but had no power after, replaced ub400 still no power, chips i was using were bought online, figured maybe the was bad, so i pulled chips from donor board and reballed,
anyhow after spending most of the day Sunday on it i have restored 5v to all ports with .45amps, but UB400 i getting hot, both ub400 and ub300 have been replaced 4-5x cant seem to figure this out, cant seem to locate short on any of the LDO lines or surrounding components, qb300/qb4000 u7000 and rom chip have also been replaced
 

2informaticos

Administrator
Staff member
First inspect for knocked off components.
Compare diode mode readings on LDO lines between all CD3215 chips.
 
Last edited:

Donlan78

Member
pp3v3_upc_tb_ldo .0009 CB408
pp1v8_upc_tb_ldod .0013 CB405
seems UB400 might be shorted again, very strange i have replaced chip 4 times, could something else be blowing the chips after replacing

replaced CB400 again, ldo readings are normal again back to 5v .28amp
pp3v3_upc_tb_ldo .470 CB408
pp1v8_upc_tb_ldod .516 CB405
ppv1v1_upc_tb_ldo_bmc .516 CB404

these ldos seem a bit low compared to working board but not shorted
c3208 .347
r3208 .347
r3209 .347
 
Last edited:

Donlan78

Member
yea pp1v1_upc_tb_ldo_bmc is present on all 4 ports. was missing on u3100, replaced chip and restored 1v1 ldo but still no power, 5.14v .26amp on all ports
 

2informaticos

Administrator
Staff member
If the board was working before, I can only suspect bad chips, bad solders, or broken trace.
Considering you've discarded knocked off components.
 
Top