Dead short on the power input of the Pinecil
#1
Hi everyone,

I've been using my Pinecil for the past few days, and it's been great (like, really! Smile ).

However, when I plugged it in this morning, it didn't turn on anymore. A quick measurement with the multi meter revealed that there is dead short (~0.5 Ohms) on the VBUS_TYPEC rail. So I did some more troubleshooting and tried to locate the point of lowest resistance, and it appears to be right in front of the RT7272B DC-DC converter. I haven't removed that IC yet (need to get my hot air station out for that), so I can't be 100% sure, but it seems likely that it's the culprit.

As for the cause of the short, I have no idea at the moment. I always supplied it from a lab power supply set to 20V, and it's been working perfectly fine right until this morning.

Three questions:

1. Has anyone else seen this kind of issue?
2. Is it generally possible to get replacement ICs from Pine64? Or should I just look in the usual places (Mouser, Farnell, Digikey, ...)?
3. @ Pine64 Team: Should I raise an RMA? (I don't think I did anything that could cause to break, so maybe I just got unlucky and got a bad unit.)

Thank you!
Markus
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#2
Just a quick update: I removed the RT7272B from the board, and indeed, it's the cause. There's a short inside the IC from VCC to SW to GND. Now I just have to hope that VCC didn't short to SW first and that the rest is fine... and find a replacement part.
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#3
Hi, I received my PINECIL (2nd run) recently and used it twice over a 24hr period. This evening I found it would not turn on at all and sure enough, same issue: RT7272B is shorted.

Removed the RT7272B, but no luck, it's not powering up nor detected as a device following the steps to enter DFU mode for firmware update. Looking at the layout, I would not think the RT7272B being absent would prevent it turning on if the rest of the device was in a healthy state, so I assume some significant damage has occurred elsewhere.
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#4
(01-23-2021, 06:10 PM)Aergan Wrote: Hi, I received my PINECIL (2nd run) recently and used it twice over a 24hr period. This evening I found it would not turn on at all and sure enough, same issue: RT7272B is shorted.

Removed the RT7272B, but no luck, it's not powering up nor detected as a device following the steps to enter DFU mode for firmware update. Looking at the layout, I would not think the RT7272B being absent would prevent it turning on if the rest of the device was in a healthy state, so I assume some significant damage has occurred elsewhere.

As far as I see, the input of RT7272B called VBUS_TYPEC which is also the same line which is available at DC input connector.
This RT7272B has an output of VCC_5V which is set to 4.2V as the comment says.
Then LP3986-33 has VCC_5V as input and VCC_3V3 is its output.
Furthermore, the microcontroller is powered from this VCC_3V3 line.

So, if the RT272B is not soldered, there should be no VCC_5V line, so there should be no VCC_3V3 line, so there should not be any action by the microcontroller as it is not powered.

To power it on, you should have some replacement power supply to power the 5V line so to have some chance to power it on at all.
However, I would check if there is no short-circuit on 5V line and 3.3V line prior powering on and also a current limited power supply would be good for troubleshooting.

It is also considerable to apply 4.2V instead of 5V because they may have reason of powering at 4.2V.
(One reason is the power loss at 3.3V LDO but other components may also have lower rating.)
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#5
I have ordered some replacement RT7272B to try then as I don't have the time to play with voltage rails to see what parts are / are not dead as it's already unfortunately delayed my existing workloads by a day. Bit of a shame this has occurred but I understand bad batches of components happen.
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#6
If still under warranty, please file RMA. However, if you have interest to fix yourselves, support team can make the RT272B arrangement.
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#7
(01-27-2021, 12:15 AM)tllim Wrote: If still under warranty, please file RMA. However, if you have interest to fix yourselves, support team can make the RT272B arrangement.

Purchased and replaced both of the SOIC and no, still dead. Voltage rails present, so assume it's chipset related. Warranty has long expired (30 days) before I even opened the box in the first place. Would it be possible to purchase a pre-populated board? Might be a solution for those with DOA units after the short warranty has expired etc.
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#8
(03-23-2021, 03:28 AM)Aergan Wrote:
(01-27-2021, 12:15 AM)tllim Wrote: If still under warranty, please file RMA. However, if you have interest to fix yourselves, support team can make the RT272B arrangement.

Purchased and replaced both of the SOIC and no, still dead. Voltage rails present, so assume it's chipset related. Warranty has long expired (30 days) before I even opened the box in the first place. Would it be possible to purchase a pre-populated board? Might be a solution for those with DOA units after the short warranty has expired etc.

Please issue the support ticket and PM me your ticket number. I will inform support team to use the date that you report this incident (assume still fall into warranty period) in this thread as claim date. The Pinecil mainboard is thin and long, that needs a protective case during shipping transport. The total price end up close to a Pinecil price, this is reason why Pine Store does not post a mainboard as spare item.
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