Vestel 17IPS71 + 17MB82S - no standby

[cruiser_]

hello there,
I am trying to fix a Walker 40 TV - it has Vestel 17IPS71 3R3 as PSU and 17MB82S for logic.

How I got here...
The TV had shorted USB connector, which I fixed. TV turned on. Ran for a few hours on HDMI input. Started to see some dark dots/patterns on the screen as seen on the photo.
I restored to factory setting. The TV has rebooted only to a blinking standby LED. It sat there for a number of minutes after which I disconnected it.
Now, after plugging it back in - there is not even a standby LED.

My 17IPS71 provides 12V, no standby though. There is no Q1 or surrounding elements at all - as per the diagram it should provide 5V standby. I must have some variant of the board?

However, the logic board provides 5V STANDBY at U46.
I checked power to ICs on the logic board, they have steady 12/5/3.3V.

What gives? I'm at loss here... Next step would probably be to hook up UART to SCART, but something tells me I should be getting standby LED in first place?

Any help greatly appreciated

[CityZen]

Re: Vestel 17IPS71 + 17MB82S - no standby

Some TVs remember when they were on before being unplugged. Seems like your TV is on, which is why there's no standby LED.

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

Some TVs remember when they were on before being unplugged. Seems like your TV is on, which is why there's no standby LED.

sure... but then where's my backlight, display and audio?

I checked SCART pins 10,12 with scope, signal stays low all the time. Shouldn't it be high ? - pulled up by 3v3_stby...

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

ok this is super weird.
multimeter on scart uart pins shows 2.78V on both, as expected.
the scope however, hovers around 0V. what the heck...?
anyways, i measured all the test points listed under 'board voltages' and they all check out.

[cheeky2]

Re: Vestel 17IPS71 + 17MB82S - no standby

Check the sb5100 in psu as they go short and give no standby. Possibly you also have faulty leds inside the screen which will give you black areas on the screen. I cannot tell from your picture of dark areas.

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

Check the sb5100 in psu as they go short and give no standby. Possibly you also have faulty leds inside the screen which will give you black areas on the screen. I cannot tell from your picture of dark areas.

hi cheeky2, the diodes all seem ok, provided 12V/24V is stable, this variant of PSU doesn't seem to provide 5v at all, nor 24V to the connector. It seems to be generated by the logic board.

re the picture - notice hundreds of tiny dark spots/lines, it's not band-like areas darkened.

i checked 11 test points on the logic board, all provided good voltage.
however, TP26 (which is a protect) is pulled low; my board has no Q10/Q43/D39 at all. That leaves 3.3, 5, 12 and 24V.

By examining voltages around D40 it seems that this line is pulled low since 24V_VCC is not there. Where would that possibly come from is beyond my understanding.

[dick_barton]

Re: Vestel 17IPS71 + 17MB82S - no standby

A photo of your power supply may be useful. It should provide 24V and the 5V is probably derived from the 12V at the mainboard.
What revision 17IPS71 is the power supply.

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

A photo of your power supply may be useful. It should provide 24V and the 5V is probably derived from the 12V at the mainboard.
What revision 17IPS71 is the power supply.

The 24v (actually higher) is present at C30/C31. I don't find any connection to the socket with that voltage.

[CityZen]

Re: Vestel 17IPS71 + 17MB82S - no standby

Are you measuring socket voltages with cables attached or disconnected? The power supply might behave differently with no load.

According to
pin 1 of CN4 might be 24V (it's a bit unclear to me), while pin 3 is the signal to turn on the power supply, and pins 10,11,12 are 12V (other even pins are ground). Pins 5,7 control the backlight, and pin 9 is the 5V standby that isn't populated.

[dick_barton]

Re: Vestel 17IPS71 + 17MB82S - no standby

Do you have +24V on L5 which is a link on your board?
You have D11, D13 & D15 on board which rectify the voltage feeding to L5 (24V)

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

Are you measuring socket voltages with cables attached or disconnected? The power supply might behave differently with no load.

According to
pin 1 of CN4 might be 24V (it's a bit unclear to me), while pin 3 is the signal to turn on the power supply, and pins 10,11,12 are 12V (other even pins are ground). Pins 5,7 control the backlight, and pin 9 is the 5V standby that isn't populated.

hi,
I've had lvds disconnected from the logic board during the measurements.

PIN1 on both the PSU board and logic board is not connected anywhere.
What's more, I traced the alleged 24V_vcc_a line that is shown on the protector circuit. It goes to two places, both with a jumper disconnected. What the heck... :|

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

Do you have +24V on L5 which is a link on your board?
You have D11, D13 & D15 on board which rectify the voltage feeding to L5 (24V)

The schematic isn't that great. The whole section around q5 is not present on the board. L5 has 26/27V on it.

[CityZen]

Re: Vestel 17IPS71 + 17MB82S - no standby

It seems 24V is only used on the PS board to supply the LED driver.

If all voltages on PSU check out, then you should focus on the main board.

Perhaps check for 3V3_STBY, which seems critical. You can probe the right-side (emitter) pads for Q1/Q3 (not present). Probe the upper (collector) pads for 5V_STBY.

It looks like Q61 switches power through FS2. If it's on, you should see voltage on FS2.

Everything goes through the main chip, the MT5820L. By "everything", I mean the standby LED and the standby power control.

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

It seems 24V is only used on the PS board to supply the LED driver.

If all voltages on PSU check out, then you should focus on the main board.

Perhaps check for 3V3_STBY, which seems critical. You can probe the right-side (emitter) pads for Q1/Q3 (not present). Probe the upper (collector) pads for 5V_STBY.

It looks like Q61 switches power through FS2. If it's on, you should see voltage on FS2.

Everything goes through the main chip, the MT5820L. By "everything", I mean the standby LED and the standby power control.

Testpoints that I have checked out (with exception of TP26 which is pulled low)
TP 1,3,4,10,12,13,15,18,21,26,222
1V2_MT58280 is at TP1, check
3V3_STDBY is at TP4, check
3V3_VCC is at TP222, check
5V_STDBY / TV_VCC is at TP2, check
12V_VCC is at TP12, check
not sure about 12V_STDBY

I'm thinking of removing Q9, which is the one pulling PROTECT down; however, from the manual it seems that if PROTECT is kicking in, I should be getting a blinking LED - and I'm not getting any.

[lotas]

Re: Vestel 17IPS71 + 17MB82S - no standby

Most likely, the firmware has flown into U10-25Q16, U12-25Q64.

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

I'm not getting clk signal for them at all. Shouldn't I be getting anything at all there during startup?

[lotas]

Re: Vestel 17IPS71 + 17MB82S - no standby

Have you checked spi flash 6pin. (sclk) on them?

[lotas]

Re: Vestel 17IPS71 + 17MB82S - no standby

On this chassis, the firmware flies and the LED does not light up completely, but it happens that they blink.

[CityZen]

Re: Vestel 17IPS71 + 17MB82S - no standby

This might be useful:

https://www.manualslib.com/manual/13...tel-Mb82s.html

[cruiser_]

Re: Vestel 17IPS71 + 17MB82S - no standby

Have you checked spi flash 6pin. (sclk) on them?

The clk is a single spike or a long pull up. Similar with Cs. Nothing that would look like data reading