Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Stj, thanks for getting involved. Regulators was one of my first thoughts. Have tested the ones I could spot and they seem to be ok. I will give it another look though.

[stj]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

solder a few wires onto points for 3v3 and 1v8 and bring them out to your meter(s)
then see what happens when it resets.

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

solder a few wires onto points for 3v3 and 1v8 and bring them out to your meter(s)
then see what happens when it resets.

Both of them drop to 0V pretty much instantly after the screen goes off, then come back up when it turns back on, though 1.8V starts at 3.2V then drops down to 1.8 after a few secs.

[tom66]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Are you sure about 3.2V? Your meter may be overshooting - try locking it in the closest range instead of using autoranging.

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

tom66 You mean the 3.2V dropping to 1.8V? Yes I'm sure. That's the pin that connects to the brightness control pin of the LED driver ic. There is a change in backlight brightness when it drops. Have checked it with two different meters and not on autoranging.

[tom66]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Thought you were talking about the main board voltage regulators then.

[stj]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

yes, i meant tapping the outputs from the regulators on the mainboard.
or tapping power at the ram or cpu or eeprom - look for a ceramic cap nearby for an easy solder point.

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Yes of course, I've got you.

There are three regulators in the attached pic. I have looked them up on the schematic for 17mb95s-2.

U5 (2v5_vcc) is giving 0V in standby and a constant 2.49V when cycling.
U9 (5v_STBY) is giving 5.45V output in standby and when cycling on and off.
U21 (3v3_STBY) is giving a constant 3.3V in all states.

I haven't found any reg for 1v8. On the schematic U14 is drawn outputting 1v8_vcc_tuner but U14 is not installed on this board.

Is U9 ok at 5.45V or is that a little high?

[stj]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

sounds high to me.

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Actually according to the datasheet for the 54528 regulator the output should be 5.5V so I think the regulators check out ok.

https://cdn.badcaps-static.com/pdfs/...00675324b1.pdf

Going to try the firmware route I guess.

[tom66]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Output voltage will vary depending on the feed-back resistors. Can be anything. 5.5V may be too high.

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Sorry, I was measuring the wrong pin of U9. Was probing the VREG5 pin which should be 5.5V. Still not too good at reading datasheets obviously.

So the correct reading of 5V_STBY/5V_VCC is 5.22V. That is the output of U9 regulator circuit as measured at the input pin of U21.

[stj]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

well i'd prefer it to be 5.1 or under, but i'm not sure 5.22 is going to be a problem - atleast not in the short term.

[tom66]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

5.2V is within tolerance for a 5V rail, up to about 5.25-5.3V would generally be OK.

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

So the plan to flash the SPI chip with Toshiba firmware has hit a snag. The chip is 16Mbit, but the .bin files from similar Toshiba models range from about 60MB to over 100MB - way too large to program onto the chip. I pulled just over 2MB of data from the existing chip. What is with all the extra data in the Toshiba .bin files?

[tom66]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

16Mbit is tiny. Are you sure you are using the right flash? The 16Mbit is probably the mboot, bootloader. The main system code will fit on a bigger, separate chip. Usually a large NAND or eMMC managed NAND device. Looks like the "SKhynix" device is the NAND, the bootloader is on the small 8 pin chip.

mboot is more or less common for all models in MB95 so you just need to find MB95 bootloader.

Note, if mboot is bad the TV will usually act dead or flash LED only.

If main flash is bad, TV may actually power on and do something (it could also flash the LED, depends where it's corrupted)

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Ah.. yet again this forum makes me feel like an idiot.

I was evidently using the bootloader flash chip. There is a H27U2G8F2CTR nand ic which must then be the system code flash. Looks like I need a more serious piece of kit to flash that one so I will probably have to look out for a replacement main board I guess.

[ReeceyBurger123]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Ah.. yet again this forum makes me feel like an idiot.

I was evidently using the bootloader flash chip. There is a H27U2G8F2CTR nand ic which must then be the system code flash. Looks like I need a more serious piece of kit to flash that one so I will probably have to look out for a replacement main board I guess.

Lol they are very hard to find and you have to match all the bar code numbers.

[stj]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

the bootloader should be able to reflash the main chip from usb / serial port.
the vestel serial port is interesting, it runs a shell at 115,000baud if i remember right.

[tn245]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

stj, interesting. Do you know how I can get it to do that?