Help Identifying datasheets and or Pinouts

[LiftedTrace]

Hi everyone, old / new nerd here. I am trying to get back into electronics after 20 years of inactivity. Never really had much experience and sort of fell away. Now I found the eevblog channel and have been binge watching David and rekindled the love I have for tinkering with things. So I am sort of on a path to reteach many of the things I have forgotten, which it turns out is quite allot.

So I have this BT speaker "Douni A5" that is non functional. I opened it up and began to check voltages. It seems I lack 5v and 3.3v anywhere on the board. Not having a schematic, and also trying to learn on the way makes things rough.
I have identified some of the major components, identified their pins from data sheets and started to trace the power pins back through the board to try and locate where the problems might be. I have hit a wall when I get to a few components I cant see to find any info on on them at all, which brings me here. I am hoping the plethora of knowledge from here, someone knows what these components are and maybe provide a link to a data sheet.  This things is Chinese in origin and fairly new, so I am not able to find any info when searching the web......which is another skill I need to learn.

The time spent repairing this probably is not worth the cost of it, but it would make me feel warm and fuzzy if I got it up and running again.
I have attached the pictures of the elusive parts.

Can anyone shed some light to what these things are, and what they do?

[fzabkar]

SY6912AFCC, Silergy, Battery Charger Li-Ion 8-Pin SOIC, marking AIQxxx:
https://www.avnet.com/shop/us/products/silergy/sy6912afcc-3074457345631026735/
https://wenku.baidu.com/view/e2e083365727a5e9856a61b3.html

It would help to see the markings on the other known ICs. In this way we could determine which characters are most likely to be date or batch codes.

It would also help to see the whole PCB, as this would place the unknown ICs in context.

[LiftedTrace]

SY6912AFCC, Silergy, Battery Charger Li-Ion 8-Pin SOIC, marking AIQxxx:
https://www.avnet.com/shop/us/products/silergy/sy6912afcc-3074457345631026735/

It would help to see the markings on the other known ICs. In this way we could determine which characters are most likely to be date or batch codes.

It would also help to see the whole PCB, as this would place the unknown ICs in context.

Thanks, the helped confirm a suspicion I had about that chip being for charging.
Attached is the whole board, minus some stuff I removed so I could follow traces around the board.

[fzabkar]

The ENxxx part appears to be a …

SY8201ABC, Silergy, High Efficiency Fast Response, 1A, 27V Input Synchronous Step Down Regulator, marking ENxyz, SOT23-6:
www.hytic.net/upload/files/2015/07/SILERGY-SY8201ABC.pdf

x = year
y =week
z = lot number

Therefore I suspect that FR71A marking may have a similar format, ie "FR", year 2017, week 1, lot # A.

AFAICT, U5, L9, U7, D7, D9 are configured as a boost converter. The electrolytic capacitor above C15 would be the boosted output. Its rating should provide a clue as to the boost voltage.

[amyk]

FRxxx is SY7901:
https://world.taobao.com/item/524767419312.htm

Unfortunately this is all the info I can find on it:
https://wenku.baidu.com/view/3c9aa170c8d376eeafaa3139.html

[LiftedTrace]

 
This is great...these get me much further than I was before. I dont understand any of this just yet, but at least now I can follow the leads on some of these and try to understand whats going on.
As a side question, How did you know what these part numbers were based on the package markings? Experience working with these packages a while and you get to know the numbers, or is there a reference package marking to part number database somewhere?

Just looking at the datasheet for the ENxyz and see the 3.3v out....thats one of that im missing 
Now I just have to track down why its not working.

[fzabkar]

www.smdmark.com/en-US
http://kazus.ru/datasheets/smd/index.html
http://www.s-manuals.com/smd
http://www.ti.com/packaging/docs/partlookup.tsp

[fzabkar]

Just looking at the datasheet for the ENxyz and see the 3.3v out....thats one of that im missing 
Now I just have to track down why its not working.

Check whether it is being enabled (pin #4 should be high).

[LiftedTrace]

Just looking at the datasheet for the ENxyz and see the 3.3v out....thats one of that im missing 
Now I just have to track down why its not working.

Check whether it is being enabled (pin #4 should be high).

Im trying to follow the flow of this thing, from the press of the power button. My brother has a working version of this in a different state. I had him take some voltage measurements for me when its on and off off all them pins on all them chips before I posted in here. So I know what they "should" be, I just haven't figured out how this thing turns on to enable these things. I suspect this BT module somehow controls it all because it looks like many of chips all terminate at the BT module.....which makes me things this module is no good.....which would also suck as it seems its unubtaininum. But if I can workout how this thing works, maybe I can retrofit a more available BT module into this and get this thing making audio again.

Thanks to you guys I at least have some data to go by now where I have some idea of what pins are doing. I haven't got to the point yet where I can see a group of components and sort of know instinctfully what is going on.

[fzabkar]

Perhaps this thread might help you to understand the principles behind your device:
https://www.badcaps.net/forum/showthread.php?t=48479&highlight=bluetooth&page=3

IIRC, the OP had a problem with a leaky ceramic capacitor on the reset pin of the Bluetooth module.

[LiftedTrace]

Wow thats a long post. Thanks for the help. Ill come back if I get anywhere or need more help. Probably take me a while to read through and understand everything in that post too.

[LiftedTrace]

Well I have made progress.
It seems it was the
“SY6912AFCC, Silergy, Battery Charger Li-Ion 8-Pin SOIC, marking AIQxxx
Chip causing the thing not to come alive.
Found it by mistake trying to remove it to see where a trace was going and ended up breaking the thing off because I didn’t know there was a pad under the chip 
The board is fine, but the chip is destroyed 
Once it was gone it fired right up 😂😂😂

So I’m asking for a bit of help again. Tracking down that thing leads to Chinese sites that I cannot read.
I searched DigiKey for “Battery Charger Li-Ion 8-Pin SOIC” but zero results were found.
Any suggestions on a possible alternative to this thing?

[amyk]

https://www.aliexpress.com/item/SY6912AFCC-SY6912A-SY6912-AIQxxx-AIQ5VA-AIQ3EA-AIQ2SZ-2A-Multi-Cell-High-Efficiency-Switching-Charger-IC/32802733056.html

[fzabkar]

full datasheet:

https://datasheet4u.com/pdf-down/S/Y/6/SY6912A-Silergy.pdf

[LiftedTrace]

Thanks a bunch for all the help. Got a new charge chip on order, hopefully that's all it was and not anything surrounding it. No schematic makes it hard to know what values things are supposed to be.