iphone 7 plus excessive battery drain and failed restore

[lots2learn]

Never noticed excessive battery drain before/after I completed the Audio IC repair many months ago.....
Now.....

1. Phone boots to the home screen ok(though the boot time is longer than usual)
2. Phone charges fine - current draw = known good
3. charging time 0-100% = known good (3 hrs)
4. battery drain excessive (standby mode/screen off - 6% per hour)
5. motherboard swapped from its own into known good housing - battery drain remains 6% per hour)

Only extra installed app was Phone Diagnostics - otherwise factory installed apps only. Then, when in order to eliminate software as cause of drain, I attempted via 3U Tools to update to IOS 14.6 to bring the problem motherboard's software inline with known good board.
1. Quick flash - fails at 80% error code 1 ✘
2. Deep flash - stuck at 60% Unknown Request(PersonalizedData) ✘

Tried restore, then DFU mode. Fails as above, remains stuck in recovery mode.


Prior soldering work(by me)
1. Audio IC jumper repair - successful - no loss of Baseband function..(done MANY months ago)
2. U3502 IC replacement (attempt to address non working vibrator) - there was a short on PP_ARC
3. Trinity replaced (went short after U3502 IC replacement)
4. U3502 replaced again (2nd attempt to address non working vibrator) - no short on PP_ARC this time but vibrator wasn't working either.
Abandoned repairing vibrator and reassembled
That was when excessive battery drain was first observed.

Could the battery drain and corruption? that has left the board in it's present state be attributed to my soldering?

[Jessa_the_Professa]

If it came in for vibrator not working (which is never a board problem in my experience) and left with rapid battery drain after you microsoldered then yes—you created a short on the board. Find it quickly with a Seek compact pro thermal cam and macro lens.

vibrator is either the vibrator part or a serialization issue—some vibrator motors seem to not work on all models. You can try the Qianli read/write software for vibrator

[lots2learn]

Just to confirm. The rapid battery drain wouldn't be the cause of the phone failing to restore? My understanding is that the failure to complete update at 80% with error code (1) is a Baseband issue. Apparently it's at the 80% point that the phone updates its Baseband. I know when heat is applied on the audio IC repair(a little to long) Baseband CPU can go south and requires a reball. But I usually test calls after an Audio IC repair and don't recall connectivity issues.(though it has been some months)

[Jessa_the_Professa]

Baseband used to be error (-1) not error (1), but iTunes errors change and are really vague. You can look at the logs to see what if there is any extra detail about why it fails restore. For example, it may say "could not update homer" which is next to audio ic---and that would be a clue. We can't say that rapid battery drain is unrelated---maybe it is related, who knows. If you have rapid drain, somewhere you have a short. Find the short with thermal cam.

[lots2learn]

I had a partial short on PP1V8_SDRAM(seated resistance of all lines PP1V8_SDRAM compared against known good were less than half of what they should be) which I relieved by desoldering and replacing Audio IC. All seated resistances on PP1v8_SDRAM now normal. I'm wondering if this could have been the cause of the battery drain?

Tried flashing on 3U Tools(again)
80% Updating Stockholm ERROR: Unable to restore iDevice(-1)

This is the same error that I had when I tried restoring the phone before relieving the partial short. Stockholm is right at the top of the board. I haven't done any microsoldering in that area.

[Jessa_the_Professa]

I would try updating it with audio ic off a couple of times. If it still doesn't update then it may be a baseband CPU problem from the work done at audio ic. You could attempt to eliminate the variable of baseband on the update by temporarily removing baseband pmu---i.e. ask it to update without trying to read/write to baseband cpu.

[lots2learn]

-desoldered audio IC reassembled.

80% Updating Stockholm

ERROR: Unable to restore iDevice(-1) (same as before)

desoldered Baseband PMU

80% Updating Stockholm

ERROR: Unable to restore iDevice(-1)

I guess Baseband CPU is ok. Any other ideas?

[Jessa_the_Professa]

You might as well replace stockholm chip and see if you can get it to pass update

[lots2learn]

The iphone 7 doesn't need Stockholm to update.
I recently verified this by desoldering Stockholm on an iphone 7 and attempting an update from IOS 14.7.1 to IOS 15.0
(Apple recently stopped signing IOS 14.8!!!)

The sequence is as follows.....
Updating Stockholm (80%)
unknown operation
sending NOR data
creating System Key Bag
Unknown Operation
Congratulations Clean Flash completed!

After the install The De Stockholmed Phone booted fine to the setup screen.

So I desoldered Stockholm off this iPhone 7 plus and reattempted an update to ios 15.01
The error is the same as before ie 80% Updating Stockholm ERROR: Unable to restore iDevice(-1)
So I now know Stockholm is not the cause of the failure to update
Which makes sense...prior to the problem occurring I hadn't done any soldering in this area of the board - there is no mechanism for failure.
I am thinking perhaps it makes sense to undo any soldering work - working backwards - that is not required for the phone to boot/update.
Attempt an update and if it still fails then redo any that is required for the phone to boot eg Trinity

[Jessa_the_Professa]

Sounds reasonable