820-3023 RAM shorted to Gnd?

Bouba148

New member
Hi Team,

PPBUS_G3H: 8.39V
PP3V42: 3.407V
PPVRTC_G3H: 3.319V

PP5V_S5: 5.150V
PP3V3_S5: 3.319V

PP5V_S3: 5.152V
PP3V3_S3: 3.320V

PP5V_S0: 5.151V
PP3V3_S0: 3.318V

PP1V8_S0: 1.805V
PP1V5_S0: 1.509V

PPVTTDDR_S3: 0V
PPDDR_S3_REG= PP1V5_S3 : 0V
at R7350 short to gnd: in diode mode : 0.0V
removed R7350: short to gnd on the 2/4 side of R7350
removed C7340, C7341, C7345 and C7346 still shorted to gnd
So my guess is one RAM chip is shorted to ground

R7402: 91.3 Ohms
At U7801:
Pin1: 5.150 V
Pin2: 3.313V
Pin5: 0V


PPVCORE_S0_CPU: 0V
PPVCORE_S0_AXG: 0V

Injected 1.5V an slowly ramped up the current step by step but nothing is getting hot except the wiresas you can see in the attached picutre.
Also in the mean time my Lab power supplies shows 0.9V when I apply 4A, and turns into protect mode.

I've noticed that Fizzl92 has more or less the "same" issue....... at https://boards.rossmanngroup.com/forum/board-repair-troubleshooting/48990-820-3023-not-turning-on

FLIR_820-3023.jpeg

Best Regards
 

2informaticos

Administrator
Staff member
STOP to touch the A limit button, when inject voltage!!!
Let it at max, you can NOT adjust the injected current; learn about Ohm law first.

In the same mentioned thread you have examples of powerfull lab power supplies; which support 20-40 A.
 

Bouba148

New member
i 2Informaticos,
Thanks for your reply.....
Those power labs will not turn to protection mode? Whats is (are? the difference(s) compared to the one I have (30V, 5A ) like in the attached picture?

dps-305bm.jpg
 

2informaticos

Administrator
Staff member
5-10A will not help in case of very low value short.
Will get them in protection mode under 1V and you will heat nothing with 2-5W; 0.7V/5A for example.
0.7V/15A is more than 10W and you will be able to sense the heat somewhere; imagine 0.7V/30A.

As already mentioned, you cannot adjust the current.
But used power supply must support the current sink by the short; before entering in protection mode.
 

Bouba148

New member
Got it, thanks
It make sense. so if I choose the 48V 10A model of Power Supply I will just have to adjust the voltage to 1.5V and the current to 10A ( Max current ) , in that case I will rise to 15W.
Maybe It's better to choose the 36V 15A model,as for the same voltage (1.5V ) I can rise up to 22.5W or the 48V 10A is enough and could be used for some other purposes......
What do you think?
 

2informaticos

Administrator
Staff member
You cannot adjust the current.
Let the A limit at max ALWAYS.
The power supply I use doesn't even have current adjust.
And choose at least 20A model...
 
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