Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

[tn245]

Hi! I've got this Bush/Vestel LED smart TV I'm hoping you can help me get going.

When first plugged in it starts off in standby and when powered on with the remote it comes up with picture and sound with no issues. 30 seconds later the picture and sound shut off with the power LED flashing continuously. 15 seconds after that it comes back on for another 30 seconds, then 15 off, 30 on, etc, etc. Apart from the initial switch on it doesn't respond to the remote at all and the only way to stop it cycling is to unplug the power.

I've attached photos of the back and the boards. PSU/LED driver is 17IPS71 which I have not found a schematic for. The main board is 17MB95M.

With the connector to the backlights removed the symptoms are the same, though obviously with no backlights, just the sound going off and on.

Does anybody have any ideas or experience with similar issues? I'm not sure whether main board or PSU at this point.

[tn245]

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

I have taken voltages along the connector between the PSU and main board. There are two rows of six pins, with the second row hiding behind the first. Helpfully the pins are not labeled and without the schematic we have to figure out what the function of each pin is.

From top to bottom row 1:

Pin  Standby   With picture   No picture    Pin Function?
1   12V     12V        12V
2   0V     0V        0V
3   0V     3.2V then 1.8V  0V        Connects to Brightness control pin of LED driver IC
4   0V     3.2V       0V        Connects to Enable pin of LED driver IC
5   2.2V    0V        0V        Drops to 0V immediately on remote switch on signal so PS_on?
6   0V     23.7V       23.8V

Row 2 just has two more 12V pins and the rest are ground.

[ReeceyBurger123]

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

I would say corrupt firmware on this one, seen it happen on a 17mb62 that was sending improper signals to the psu. Unplug the mainboard from the psu and see if the voltage still fluctuates you may need to jumper the psu to get it to turn on.

[tn245]

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

Thanks ReeceyBurger. I'm not clear how to jumper it to turn it on. I was thinking pin 5 needs to be shorted to gnd as it drops to 0V when the power button on the remote is pressed. But with the main board removed that pin is at 0V anyway.

With the PSU isolated I have ~ 12V pin 1, about 1.8V pin 3, 23.8V pin 6 and the rest 0V. When isolated there is also a faint tick sound on the PSU every 3 seconds and on each tick pin 1 jumps from 11.7V to 12.3V and back down.

[ReeceyBurger123]

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

Remove the psu from the main board and measure the pins, find the pin that has 5v on it and use a 100-500ohm resistor and short that pin to ground that should be enough to power the psu on then check the voltages if its good it may bring up the backlights. I think that this psu shares the 17pw71-2 schematic.

[tom66]

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

I would expect corrupted firmware, have also heard of this happening when accessing certain apps in the menu e.g. Netflix/iPlayer. Since TV works for 30 secs, you MAY be able to update firmware over USB port if you can get hold of a copy. If you have an existing same or similar TV you may also be able to copy off the firmware from the set using the service menu (Copy NVM) available on some Vestels.

[ReeceyBurger123]

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

The pain with these sets is that you cant just interchange/swap parts they have to be exact and for the specific panel ohh vestel your tvs are far from smart

[tn245]

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

ReeceyBurger: Thanks. I had quoted the voltages with PSU removed just about your last post and there's no pin with 5V. It has 12V when isolated which seems to be used as the standby voltage by the main board. I will check out the 17pw71-2 schematic thanks.

[ReeceyBurger123]

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

ReeceyBurger: Thanks. I had quoted the voltages with PSU removed just about your last post and there's no pin with 5V. It has 12V when isolated which seems to be used as the standby voltage by the main board. I will check out the 17pw71-2 schematic thanks.

No problem I think that this is firmware tbh if you have no luck with the psu try flashing the firmware, read what Tom66 said.

[tn245]

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

tom66 thanks! I have no idea where to even start looking for firmware but I will get looking into it.

[tn245]

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

Would I be looking for firmware based on the main board or TV model number?

[tn245]

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

I also note I'll probably need to use the remote to do the firmware update, and it doesn't respond to the remote at all once it's got into its on-off cycle.

Maybe best to look out for a compatible replacement main board?

[tom66]

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

Would I be looking for firmware based on the main board or TV model number?

Product code... a 7 digit number on the back of the set... IIRC there's a database somewhere with tons of firmware files on it... can't find it right now though.

[tn245]

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

Can't find any Bush firmware but Toshiba have firmware available for their Vestel TVs that use 17mb95 main boards. I'm guessing one of those would work.

As expected I'm not able to do a flash from the TV usb drive in the normal way as the TV does not respond to any input. I'm thinking about getting a cheap eeprom programmer and removing the 25L chip and flashing it that way.

[tom66]

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

That might work - note it's not an EEPROM but an SPI/Serial flash, so make sure your programmer supports it. Copy original data off before flashing. Also, maybe best to replace entire chip, as failure is likely due to flash wear out rather than actual corruption.

[tn245]

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

Awesome. Was thinking about one of these:
http://www.ebay.co.uk/itm/24-25-Seri...-/400841941718

It says it can do MX25L1605. The ic on the board is 25L1606E, but I guess I can replace the ic with an equivalent SPI chip more readily available here?

[stj]

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

wouldnt surprise me if it was a bad regulator or related part on the mainboard on those - they are very similar to the boards in LG's

[stj]

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

btw, the system boots by reading the bios from the flash into ram.
then running it.
if the tv starts up and runs then the bios is probably o.k.

[tom66]

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

It says it can do MX25L1605. The ic on the board is 25L1606E, but I guess I can replace the ic with an equivalent SPI chip more readily available here?

Depends if the registers on-chip are compatible, sometimes they will not be, so be careful. Unlike EEPROMs most flash ICs aren't natively interchangeable.

[tn245]

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

Ok thanks Tom. So best to order the same chip from China then I guess. Will probably try rewriting the existing one while I wait for it to come anyway.