Dell Inspiron 3585 CAL51 LA-F121P

[Eniaro]

So this PC has been running really slow and won't charge

It turns out the DC-IN jack was broken which I replaced. But it still won't charge.
I inspected the board and RC639 is fractured

I plan to replace it however the volts aren't stated in the schematics
https://www.badcaps.net/forum/showthread.php?t=97207

I don't really see how RC639 could prevent the PC from charging should I be looking for something else?

[mon2]

Re: Dell Inspiron 15 LA-F121p Slow and wont charge

really slow and won't charge

Linked to a low rated power supply or the logic board believes the power adapter is not the proper rating.

What is the power of the adapter? Does the BIOS show the same details?

Otherwise, the logic board will throttle the CPU speed and will not charge the battery. Sluggo time.

[Eniaro]

Re: Dell Inspiron 15 LA-F121p Slow and wont charge

bios and on startup, something about PSU wattage cannot be determined...
45w psu original one it came with.

just trying to save on shipping since the resistor seems to be a few cents I'd like to purchase whatever else I'm missing. On that topic what voltage resistor is it?

[mon2]

Re: Dell Inspiron 15 LA-F121p Slow and wont charge

See attached.

Often, PQ1 gets damaged. This mosfet acts like a switch between the center pin of the power adapter and the logic board.

When the mosfet is enabled, by default since the gate voltage is 5v, the communication can occur between the logic board and the power adapter using the 1-wire communication protocol.

Using this protocol, the details of the adapter can be extracted.

Meter in dc volts mode (20v is ok). Measure the voltage to ground of each pin on this mosfet.

So red meter probe to pin #1, black meter probe to ground (shield is ok).

Repeat for other pins on this device. Have the adapter plugged in and plugged into the wall socket.

Post each measurement.

Do you have soldering tools, flux and wire?

From where will you buy the parts? Digikey?

The RC639 that is damaged is not linked to this fault. It is available from Digikey. Do not order anything till we review the ps_id circuit.

[mon2]

Re: Dell Inspiron 15 LA-F121p Slow and wont charge

Attaching some replacement parts from Digikey:

PQ1 mosfet:

https://www.digikey.com/en/products/...FDV301N/458851



RC639 - order a 100 pcs since they are easy to lose and small:

(10k 0402 SMD size)

https://www.digikey.com/short/5rhw85dh

First, you should measure the voltages and then we can bypass PQ1 for initial testing.

[manol278]

Re: Dell Inspiron 15 5570 Plugged in not charging

I have Dell Inspiron 15 5575 Compal CAL51 LA-F121P Rev 1.00(A00).
Burnt diode.The laptop only blink white light.No start-No screen.In foto i removed the diode. I cant find which part is. Can anybody recognize the diode? equivalent diode?

[mon2]

Re: Dell Inspiron 15 5570 Plugged in not charging

Do you have any part markings from this part?

[manol278]

Re: Dell Inspiron 15 5570 Plugged in not charging

I think CG5

[SMDFlea]

Re: Dell Inspiron 15 5570 Plugged in not charging

I think CG5

search for the part with the boardview - https://www.badcaps.net/forum/showthread.php?t=97207

[manol278]

Re: Dell Inspiron 15 5570 Plugged in not charging

Boardiew part is pd1....????
It means?

[mon2]

Re: Dell Inspiron 15 5570 Plugged in not charging

PD1 is a dual line unidirectional TVS diode for 5 volts.

The part will be passive and remain out of circuit unless a transient event spikes the voltage higher than 5 volts. Then it will shunt the event to ground to protect the line from damage.

Datasheet is attached. It is a common part that can be replaced by many other vendors.

From where do you purchase your parts?

[manol278]

Re: Dell Inspiron 15 5570 Plugged in not charging

Thank you. I replaced it from donor motherboard and work fine.

[Eniaro]

Re: Dell Inspiron 15 LA-F121p Slow and wont charge

See attached.

Often, PQ1 gets damaged. This mosfet acts like a switch between the center pin of the power adapter and the logic board.

When the mosfet is enabled, by default since the gate voltage is 5v, the communication can occur between the logic board and the power adapter using the 1-wire communication protocol.

Using this protocol, the details of the adapter can be extracted.

Meter in dc volts mode (20v is ok). Measure the voltage to ground of each pin on this mosfet.

So red meter probe to pin #1, black meter probe to ground (shield is ok).

Repeat for other pins on this device. Have the adapter plugged in and plugged into the wall socket.

Post each measurement.

I got distracted from this one for a bit my apologies


I'm not sure which is Pin 1... I think pin 1 starts at the bottom left and counts counterclockwise if so...

Pin 1 5.15 V
Pin 2 194.4 mv
Pin 3 194.0 mv

IF not ...

Do you have soldering tools, flux and wire?

From where will you buy the parts? Digikey?

The RC639 that is damaged is not linked to this fault. It is available from Digikey. Do not order anything till we review the ps_id circuit.

I do have solder and flux... on the fence with flux still testing out what works well for me

[Eniaro]

Re: Dell Inspiron 15 5570 Plugged in not charging

Bump?

[mon2]

Re: Dell Inspiron 15 5570 Plugged in not charging

@Eniaro, see attached.

The mosfet @ PQ1 appears to be ok but continue the checks.

Remove all power. Meter in resistance mode.

What is the resistance of the resistor @ PR1 ? It should be ~33 ohms. Confirm it. Meter probes across PR1.

Next, power up with the official adapter and measure the voltage to ground on each side of the same PR1 resistor.

Red meter probe on pin #1 (PR1). Black meter probe to ground. Voltage reading?
Red meter probe on pin #2 (PR1). Black meter probe to ground. Voltage reading?

Also interested in the voltage to ground readings of PR5 (~2k2 pull-up resistor).

Post all readings.

[Eniaro]

Re: Dell Inspiron 15 5570 Plugged in not charging

PR1: 032.9Ω
PR5: 2.168Ω

PR1: Pin1 to ground 194.6mv
PR2: Pin2 to ground 241.6 mv

PR5: Pin1 to ground 241.6mv
PR5: Pin2 to ground 3.349 V

[mon2]

Re: Dell Inspiron 15 5570 Plugged in not charging

Remove the diode at PD1 and measure again the voltage to ground of the PS_ID signal line.

Apply ample flux and low air pressure till the solder melts.

[Eniaro]

Re: Dell Inspiron 15 5570 Plugged in not charging

PR1: 032.9Ω
PR5: 2.168Ω

PR1: Pin1 to ground 194.6mv
PR2: Pin2 to ground 241.6 mv

PR5: Pin1 to ground 241.6mv
PR5: Pin2 to ground 3.349 V

Remove the diode at PD1 and measure again the voltage to ground of the PS_ID signal line.

Apply ample flux and low air pressure till the solder melts.

I've never really been great with the hot air station. I either blow things away or fall asleep of boredom waiting on something to happen

Flux (not the one I'm using now, it crystalizes after cooling -really annoying), A dab of Sn/Pb solder on each leg, and solder wick... is the method I use.

Any way...


PR1: 033.2Ω
PR5: 2.168Ω

PR1: Pin1 to ground 3.281 V
PR2: Pin2 to ground 3.282 V

PR5: Pin1 to ground 3.282 V
PR5: Pin2 to ground 3.350 V

I'm assuming PD1 is dead?

There appear to be four TVNST52302AB0_SOT523-3 packages on the motherboard. In addition to PD1, PD5, and PD6, I think EU4012 is the same package type. It appears to be connected to Pin 2 of JFP1, the fingerprint reader connection. However, when I look for it on LA-F115P TOP.pdf, it appears in the middle of the board, nowhere near the fingerprint reader connector. Now I need to examine the motherboard under a scope to find EU4012.

I'm just looking for all the spare TVS diodes that I can harvest from donor boards to replace blown PD1, since it seems to be a common failure point (by design).

This website was started because of Bad Capacitors (and has evolved over the years...) I'd replace the tvs diodes with new ones because tvs diodes might be the new bad caps

[mon2]

Re: Dell Inspiron 15 5570 Plugged in not charging

PR5 resistance is in Kohms or ohms? Guessing it is a typo?

What is the voltage to ground of PD1 pin #2?

[Eniaro]

Re: Dell Inspiron 15 5570 Plugged in not charging

Not mistyped It is indeed a 2K resistor


I assumed PD1 pin 2's pad since PD1 was removed

PD1 Pin 2 pad to ground: 3.821V

PD1 itself detached from board PD1 Ground pin to PD1 Pin 2: 0.079V


If PD1 is indeed bad

I found these on mouser but I'm unsure which will be meet/exceed manufacture spec