820-3332 No charger light

[grmacs]

Hi there,

I'm very new to logic repair but have had some success and I've been watching the videos. I'm trying to troubleshoot the charger circuit on 820-3332. I was able to very 3.42 to SMC and I have 3.42 at U6901 pin 5 but no SMC BC ACOK there (.42mV). Also at R5087 I have 3.42 on pin 2 and .42mV on 1. Is the SMC toast? other things to verify?

 

[2informaticos]

First of all, welcome to the forum!

SMC_BC_ACOK is controlled by U7000 (ISL6259), not by SMC.
There is very low chance that SMC (or U6901) input gets leakage and kills the signal; supposing R5087 is good, of course.

You didn't say anything avout PPBUS_G3H (exact) voltage.
However we need few voltage readings on U7000 pins; 1, 2, 3, 9, 12, 13, 14, 15, 17, 19, 20, 27.

 

[grmacs]

PPBUS_G3H = .201V at f7040
U7000 has a pit in the top of it I just discovered...
Here are the readings:
1-15.5v
2-16.1v
3-7.6v
9-2.24v
12-3.39v
13-3.35v
14-42mV
15-.3mV
17-.228V
19-5.5V
20-5.5V
27-7.1mV

 

[2informaticos]

"3-7.6v"
Are you sure about this?
There should be 4V aprox.
Check R7010/11; can be U7000 fault also.

Also check and post exact resistance between pins 27/28.

 

[grmacs]

Thanks for your help. I replaced the ISL being that it had a hole in the top. I didnt notice anything at all on the board at first but after you pointed me to that chip I saw something on top and scraped it and apparently it was a blister that lead to me discovering the pit in the chip. Not sure if I blew off R7002 when I removed the ISL but I just noticed it is not there which is definitely a problem...
I'll check the others you pointed me to.

 

[grmacs]

so after putting r7002 on the board my readings on u7000 are the same except the following:
pin 9 has dropped to 9.2mV??
27 is at 4.5
14 & 15 still about .5mV

I checked R5441 per the drop in voltage on pin 9 and it is reading 7.6k (schematic says 45.3k - so I assume this is bad but didnt know if there could be something on the circuit affecting the measurement besides the actual resistor).

 

[2informaticos]

I said you to check the ACIN input resistors.
And some resistors on the pins 27/28...

 

[grmacs]

Oh sorry wasn't sure if those were still needed w new isL and changes in voltages from that.
7010 - 86.4k ohm
7011 - 35.2k ohm
21.2 ohms btween pin 27/28

 

[2informaticos]

You cannot have 7.6V at ACIN pin with these values; unless U7000 is bad...

 

[grmacs]

that is now reading 3.92V after changing the ISL

 

[2informaticos]

Then post again voltage on all mentioned pins of U7000; actual and correct values, please.

Also check resistance between pins 17/18.

 

[grmacs]

Ok...
u7000
1-15.5V
2-14.83V
3-3.92V
9- 9.4mV
12- 3.4V
13 - 3.38V
14-.6mV
15 - 46.4 mV
17 - 171.9 mV
19 - 5.5V
20 - 5.5V
27- 3.6 V (drops while checking)
resistance between 17&18= 3.8 ohms

 

[2informaticos]

Change U7000 again; pin 1 has incorrect voltage.
Post first diode mode to ground at PPBUS_G3H.

 

[grmacs]

diode ppbus_g3h to ground = .436V w no isl. Is that what you meant?

 

[2informaticos]

Is good, no short; check it again after resolder new chip.
Change U7000 and comment...

 

[grmacs]

after new u7000 0v drop diode ppbus_g3h. I haven't put power to the board since changing u7000

 

[2informaticos]

If you have short on PPBUS_G3H after changing U7000, remove it and check again.

 

[grmacs]

ok i pulled, checked +no short. put back on and @.419V drop w diode check to ground on {PPBUS_G3H

 

[2informaticos]

Did you check PPBUS_G3H voltage now?

 

[grmacs]

oy 18mV and rising...