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820-2936a missing pp5v_s3

2informaticos

2informaticos

Administrator
Staff member
If no voltage, post resistance to ground (diode mode).
Must find why no voltages there.

Also post voltage and resistance for EN0.
 
2informaticos

2informaticos

Administrator
Staff member
"l7260 0.036"
That's no good.
Remove power and wait 20s before measure diode mode on board...
Measure both directions, red and black at ground.
 
2informaticos

2informaticos

Administrator
Staff member
0.007 in diode mode is aprox 10-15 ohms in 200ohm scale.
Something is strange with your measures...

Put red probe on ground and touch the coil with black probe; note the value.
Invert the probes and note the other (reverse) value.
 
2informaticos

2informaticos

Administrator
Staff member
So both lines shorted to ground practicaly...

How do you explain these values then?
"L7220 0.125
l7260 0.036"

If I'm not sure about your values, my replies will not help you.
 
K

Kyle93

Active member
at this point i believe there is a short inside the board. When injecting 5 volts in the line u7200 gets boiling hot but parts of the board get hot that have no components on them. Removed all capacitors on the line and still have a short
 
K

Kyle93

Active member
worked on this board more and removed the short which was u4800 but now all of my voltages are off ppbus on f7040 is only 1.1V. What can cause this? What to check now?
 
K

Kyle93

Active member
c7334 near u7200 is also very warm to the touch. not sure if this means a short inside the board since this is no stuff
 
2informaticos

2informaticos

Administrator
Staff member
Remove F7040 and see if get correct voltage at C7040.
If OK, then the problem is not on the power supply; which seems to be correct, but is better to discard 100%.

Looks like a short around U7200, or the chip itself.
Check Q7260 and high-side of Q7220 for short.
Also check at VREG3/5 and VREF outputs...
 
K

Kyle93

Active member
there was correct voltage on c7040 after f7040 was removed

q7260 and q7220 do not have shorts.

vreg3 0.113 v vreg 5 0.083v vref 0.113V

cant be the chip itself. already replaced it with new
 
K

Kyle93

Active member
dummy me soldered q7260 backwards. I replaced it again, soldered it in right position and now I have new voltages and nothing is getting hot. PPBUS_G3H back to 12.60V

pp5v_s3 0.602V

PP5V_S5 0.482V

what to check next?
 
K

Kyle93

Active member
should u7200 be replaced again now since it was burning hot so many times while trying to find the short?

pin 16 12.60V
pin 17 0.489V
VREG 3 0.601V
VREG 5 0.489V
 
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