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Old 03-11-2022, 02:45 AM   #1
AJ847.63e
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Default A1708 820-00840 Missing PP1V1_UPC_XA

Hi All.

Just wanted to see if I can get some assistance with a A1708 I'm working on. Board while looking clean had it's liquid marker tripped by U2890. Board started off as fluctuating between 0.0157A @ 5.1762V to 0.0132A - 5.1751V 0.190A. Went through and checked the CD3215 bootup table on logiwiki. Found all LDOs (step 2) are present bar P1V1_UPC_XA_LDO_BMC which is completely missing regardless which USB port I use and P1V1_UPC_XB_LDO_BMC which is 0.280V, Logiwiki noted that's likely a faulty TBT rom, and judging the sticker near it had tripped I decided to remove the rom and low and behold there was junk under it. Replaced it and now the boards up to 0.0230 with a short dip to 0.01 and a short spike to 0.04 than rinse and repeat.

After replacing the TBT rom it shortly did get warm, not hot but it was evaporating IPA after maybe 40 sec or so, but after leaving it on for a minute or so and power cycling it's no longer doing that. Nothing else seems to be getting hot. Confirmed all traces between the TBT rom and the CDs are ok, as logi also mentions they often break.

What else could be causing PP1v1 to be missing? Besides bad CDs hopefully because I do not have replacements.

Thanks for your assistance.
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Old 03-11-2022, 04:33 AM   #2
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

Meter in diode mode.

Red meter lead to ground.

Black meter lead to point to test.

Check the diode mode reading of each CD3215 LDO rail.

Post the values.

https://boards.rossmanngroup.com/thr...h-ports.57331/
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Old 03-11-2022, 06:21 AM   #3
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

Thanks. I get 0.485 diode mode for XA using the test point and 0.486 for XB using it's respective test pads. When I replaced the TBT ROM chip I did so with a ROM from a 820-01598 as that was all I had and was hoping the FW would be the same. Do we know if their the same or different? Are they flashable?
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Old 03-11-2022, 06:32 AM   #4
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

Should also mention both CD fuses have been checked and both have 5.12v when their respective USB port is connected.

Just checked the voltages on the no stuff caps as well as I noticed in the post you linked to they requested those.


C3120 pad 1: 5.12v / pad 2: 4.19V
C3121 pad 1: 4.56v dips to 4.31 than back up
pad 2: 8.36 fluctuates all over the place quite rapidly. Lowest value was 6.35v.

C3220 pad 1: 5.16v / pad 2: 7.2v
C3221 pad 1: 5.15V dips to 4.82v than back up
pad 2: 10.86V dips to 9.75v after about 20 sec but bounced back to 10.86 immediately.

Last edited by AJ847.63e; 03-11-2022 at 07:21 AM..
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Old 03-11-2022, 06:40 AM   #5
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

https://boards.rossmanngroup.com/thr...equired.60466/
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Old 03-12-2022, 10:38 PM   #6
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

Well, that's a surprise. Normally Apple write protects the chips so there not flashable. After the board numbers they usually have a dash something do we know what that denotes? I'm assuming probably a region designation. I did get a 820-00840-A donor board today, but the board I need a rom for is 820-00840-1. Does that matter? I've ordered some TBT roms from our local electronics supplier incase it does need to be the exact same one and will flash one once they arrive.
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Old 03-13-2022, 04:10 AM   #7
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

For programming chips, has anyone tried the chipsetpro device? I haven't purchased a USB programmer yet so I've been doing some googling to try see what models people recommend.
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Old 03-13-2022, 07:07 AM   #8
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

I would backup the rom contents of your existing flash and apply a fresh image of the 820-00840-A onto the same device. From internet searching, do not see a dump mention of a 820-00840-1 specific rom.

The flash device is industry standard SPI interface.

So the access will occur over standard SPI read commands. Unless the logic board will extract and compare the flash device IDs, doubt there will be any issues.

Any SPI compatible programmer will work as long as the voltage is supported for the same device.

Confirm with the chip database that your exact flash is supported by the tool you wish to buy.

We are considering to buy the U301 tool for the rom dumps.
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Old 03-14-2022, 03:46 AM   #9
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

I ended up buying the BY-301 tool off phonefix and the RT801 off Ali will backup the existing chip once they arrive. Apparently the BY-301 has built in backups of all the ROM files for all the USB c boards 2016 - 2020 which is nice.
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Old 03-14-2022, 04:32 AM   #10
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

Excellent. They do not list a dump for your exact logic board but do mention 820-00840-A. So likely it will be the same and suitable for your 820-00840-1.

After the tool is received, can you post all of the TBT rom dumps here?

It will be helpful to all techs.

Thanks.
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Old 03-14-2022, 06:50 AM   #11
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

000840 should have CD3215C00, but USB-C controller firmware also depends on the USB-C controller revision (B01/B03/C00).
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Old 03-14-2022, 08:34 PM   #12
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

Thanks Piernov. Sure, once the tool arrives I’ll upload the FWs to this thread.
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Old 04-13-2022, 09:31 AM   #13
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Default Re: A1708 820-00840 Missing PP1V1_UPC_XA

Quote:
Originally Posted by AJ847.63e View Post
Thanks Piernov. Sure, once the tool arrives Iíll upload the FWs to this thread.
.

Thanks, watching with interest
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