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820-00840 no SYSCLK_CLK12M_SMC

2informaticos

2informaticos

Administrator
Staff member
SMC is the master, the one which set PPBUS_G3H level.
So communication through corresponding I2C bus is required.

Remove U5274/R5275 (as per case) and check if any voltage appears at PPBUS_G3H.
 
2informaticos

2informaticos

Administrator
Staff member
Yeah, on old boards is active low; its name ends in _L.
ISL6259 will deliver 12.25V (3 cells battery case) with 0V at reset pin (reset enabled).
In such case no communication is possible through I2C with SMC.
You can force now 3V at ISL9239 reset pin (SMC_RST_IN); it will enable reset in this case.
Don't forget to isolate SMC_RST_IN for the rest of board.
U7000 should enable reset for SMC too (0V at SMC_RESET_L) and you can check if some voltage appears at PPBUS_G3H.
I don't know untill which point has similar behaviour with old boards...
 
M

melvinvdb

New member
Well nothing interesting is connected to SMC_RST_IN or SMC_LSOC_RST so i've applied 3v to them (no keyboard connected).
Result is SMC_RST_IN low, SMC_RESET_L low and BUF_SMC_RESET_L low.
No voltage at PPBUS_G3H.

Very interesting things happen though when I disconnect the 3v.
SMC_RESET_L gets high again (3.41v) but BUF_SMC_RESET_L gets to only 1v.
After disconnecting charger and reconnecting same thing happens. Than waited some time reconnect charger and BUF_SMC_RESET_L is 3.41v again.
I do have U8510 (SLG4AP4998).
I though you may have found the issue but after waiting and reconnecting charger it's 3.41v again. So either the SMC is doeing weird things or U8510 may be bad.
 
2informaticos

2informaticos

Administrator
Staff member
Change U8510, if possible.
Or try the bypass at least (chip removed); just to see what happens with PPBUS_G3H.
 
M

melvinvdb

New member
Ok I've removed U8510 and replaced it with a bypass resistor just for the SMC_RESET circuit. When the 20v works I'll place a u8510 from a donor board.
Anyway the 1v issue is gone. Still no difference on the other rails. Still nothing on PPBUS_G3H.
 
M

melvinvdb

New member
I don't have them available but can order them. Will take two week though.
So at this point I think that would be the best option.
Also If that doesn't work I'm thinking of replacing the SMC.
I have a china donor board with the same 820-00840.
Also on ebay there are SMC chips for sale. TM4EA23IH6ZXRI which matches exactly.
Unsure if that might be an option.
The serial number and manufacturing date are burned in the SMC right? So changing SMC would change serial number?
 
2informaticos

2informaticos

Administrator
Staff member
CD3215 chips boot in master/slave pairs.
The second one (slave) boots from UART lines of first one (master).

These new boards require lot of work to collect necessary information for repairs.
I appreciate the time you take on this one.
Should be good to check an working board and see what happens with PPBUS_G3H when SMC_RST_IN is forced high.
You can see then if U7000 requires communication with SMC, in order to generate PPBUS_G3H.
 
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