TCL 55P607 / 55P605 tcon dump

[howardc64]

Researched a bit into floating gate (Both NOR and NAND flash memory cell use floating gate mechanism to storage bits) Found this video that provides a simple explanation of floating gate. Its basically through trapped electrons.

Sounds like floating gate will loose charge over time (and at high temperature) so some people suggest to "recharge" them every couple of years ( link ) Perhaps thats the failure mode of these TCON's NOR flash.

Based on this understanding, I imagine just re-flashing the NOR flash will "recharge" each gate to close to their original full potential (minus age releated wear) so reflashing the corrupted NOR flash on these TCON should have good longevity. However, I don't know if these NOR flash do things like periodic internal writes to refresh the charge.

Anyway, a flash memory engineer would be able to provide much more insight.

[howardc64]

Found datasheets for GD25Q41BT and GD25Q40C*, can't tell much differences. Here are some info

Datasheets

https://www.alldatasheet.com/datashe.../GD25Q41B.html
https://www.gigadevice.com/product/f...flash/gd25q40c

Decoding Chip Markings

(pg 46-41 of GD25Q41B datahseet)

Q = 2.7-3.7V
40/41 = 4Mbit
B/C = Revision
T = SOP8 150mil (package spec)

Datasheet Dates

Data sheet revision history of GD25Q40C* shows initial date of 2/3/2016 (pg 63) which is before manufacturing date of these TCL TVs (2017) with this TCON board. So these 2 NOR flash is likely substantially the same spec wise.

Data Retention Lifetime

GD25Q40C datasheet feature set (pg 4) does say 20 year data retention typical. So maybe its good to replace the flash that is near 50% of its typical data retention duration. The GD25Q41BT in a 2017 TCL TCON would be 8 years old now while a new GD25Q40C is presumably much younger and with different semiconductor fabrication chacteristics.

[howardc64]

seem to be many differences. At this point, I'm not sure if it's just a different version, or a bad dump.

Yes, bad dumps have many difference compared to good.bin but many are just flipped bit 3 in a big endian nibble (bit 4 3 2 1) so quite a few numbers incrases by 4.

your bad.bin compared to my 2 bad dumps differ by only 2 bits. So these corruptions are happening in a very similar way.

[howardc64]

googled "25Q40 corruption" This TCL TCON isn't a unique case. Samsungs and some monitors also have failures as lotus mentioned. Found the attached document on NOR flash power up down sequence.

I guess its easy to expect these NOR flashes are simple non volatile storage devices. But in reality, its quite complex. Physics of storage mechanisms of storage devices are inheriently analog and often in the realm of quantum mechanics as designs aim to get more bits / area. These NOR flash, have pre-stored parameters called "configuration settings" that are loaded into internal registers during power up to start the device. These configuration settings include many manufacturing details including yield improvements (substituting random bad blocks from manufacturing with spares) and other manufacturing varying characteristics of analog devices manufacturing.

Document details out the proper voltage power supply sequence during power up, shutdown, brown outs etc. If not properly handled, can cause error during this initial "configuration settings" transfer to internal registers which then can result in stored data bit filps. The complexity involved seems quite high for a simple TV board designs to include all the cases.

Anyway, maybe power sequence of the TCON isn't robust enough for this complex device and encounter this error at a low random frequency. Maybe newer version of 25Q40 is more robust at handling less robust power sequences as designs improved over time to handle problems observed in the field. Probably need NOR flash design experts to have any real insight.

https://www.renesas.com/en/document/...-bO6Dr4Nzn8ZTR

[ziddey]

Reassuring Do you still have the failed tcon flash image? Would be interesting to compare it with the 2 failed ones I posted to see how similar.

seem to be many differences. At this point, I'm not sure if it's just a different version, or a bad dump.

[howardc64]

For what it's worth, I've been using the tv with the original reflashed tcon board just about daily since I made this point, so almost 3 years now. TV has taken multiple roku updates without issue, although I imagine there probably haven't been any tcon updates, if that even was to blame originally. 25Q41BT

Reassuring Do you still have the failed tcon flash image? Would be interesting to compare it with the 2 failed ones I posted to see how similar.

[ziddey]

For what it's worth, I've been using the tv with the original reflashed tcon board just about daily since I made this point, so almost 3 years now. TV has taken multiple roku updates without issue, although I imagine there probably haven't been any tcon updates, if that even was to blame originally. 25Q41BT

[howardc64]

I don’t know, put a regular one, why put a high-temperature flash in T-CON.

Thanks. Just checking. 85C part seems good enough as you suggest

[lotas]

I don’t know, put a regular one, why put a high-temperature flash in T-CON.

[howardc64]

lotas There are many GD25Q40* available, most differences are previous (GD25Q40C) vs newer versions (GD25Q40E, digikey in US require min 9000 tape reel purchase) and max temperature rating (85C vs 105C vs 125C) Most easy to get is GD24Q40C 85C part. Does this matter?

[howardc64]

Here you need to experiment, there are motherboards where there was a flash GD and after replacing it with W it did not start.

Thank you. I'll replace with same brand. I think I only see GD on these TCONs so far.

[lotas]

Here you need to experiment, there are motherboards where there was a flash GD and after replacing it with W it did not start.

[howardc64]

The problem is precisely in this flash (GigaDevice 25Q41BT), it is installed in some monitors and there was a problem in the firmware, after replacing it with 25Q40 there were no problems.

Great info. Thanks. Will order 25Q40. Does Giga Devices or Winbond brand matter?

[lotas]

The problem is precisely in this flash (GigaDevice 25Q41BT), it is installed in some monitors and there was a problem in the firmware, after replacing it with 25Q40 there were no problems.

[howardc64]

Acquired another TCL 55S405 with backlight but no screen. Failure is exactly same with TCON flash corruption. Looks like TCON ST5461D04-1-C-7 is prone to this failure. Here are some stats + failed ROM dumps and comparisons.

- 2x TCL 55S405 with TCON board ST5461D04-1-C-7 with backlight on and display blank
- Both TCON flashed with good.bin from post #1 and TV works.
- Diffing good.bin with both failed flash TCON image shows mostly single bit errors often in the same bit within the byte.
- Diffing both failed TCON flash image shows they are EXACTLY the same except a single bit.

So why is this failure so common? (ebay seller seems to sell many of these flash chip preflashed with good image, presumably same as good.bin)

- system update caused corruption?
- flash chip random corruption? These are NOR flash technology which is for high durabiity and reliability

Will use these TVs with good.bin flashed TCON and see if stays working. Also will electrical tape the buffer board guard as preventive for future flex+COF failures.

Both failed TCON flash image attached for anyone curious

[howardc64]

Thanks Diah Yours and post #1/#5 downloads fine now as well as pics showing properly in #1. I guess server glitch.

My rom file differs (a bunch of random bytes) from these. TV (TCL 55S405) at a travel location so will install the flashed tcon in 2-3 months and report back.

[lotas]

Keep getting "Invalid File Specified" when trying to download the ST5461D04-1-C-7 T-Con flash rom file. Anyone else having access difficulty? Pics on post #1 don't post either.

I downloaded from the first post and from the fifth one too, everything is fine, but some photos are now opening with errors....

[Diah]

Keep getting "Invalid File Specified" when trying to download the ST5461D04-1-C-7 T-Con flash rom file. Anyone else having access difficulty? Pics on post #1 don't post either.

how about this

[howardc64]

Keep getting "Invalid File Specified" when trying to download the ST5461D04-1-C-7 T-Con flash rom file. Anyone else having access difficulty? Pics on post #1 don't post either.

[gpatadia]

thanks