Philips 170S4 goes blank when video signal applied

[redart]

Hi,

I have a Philips 170S4 LCD monitor that I've been troubleshooting with no luck so far. Screen turns on and displays menu, 'no video input', 'entering sleep mode', and 'check cable connection' messages fine, however as soon as I plug the vga cable in it goes black. Note that the backlights are definitely on - it's just 'displaying' a black screen. Have tried it on 2 computers and with different cables, and at different resolutions. When resolution is changed you can see the screen resetting, but always comes up black. I'm thinking it must be the video board that's bad. Any thoughts ?.

[PlainBill]

Re: Philips 170S4 goes blank when video signal applied

Hi,

I have a Philips 170S4 LCD monitor that I've been troubleshooting with no luck so far. Screen turns on and displays menu, 'no video input', 'entering sleep mode', and 'check cable connection' messages fine, however as soon as I plug the vga cable in it goes black. Note that the backlights are definitely on - it's just 'displaying' a black screen. Have tried it on 2 computers and with different cables, and at different resolutions. When resolution is changed you can see the screen resetting, but always comes up black. I'm thinking it must be the video board that's bad. Any thoughts ?.

You're probably right. Have you verified the resolution you are using is one of the resolutions supported by the monitor?

PlainBill

[redart]

Re: Philips 170S4 goes blank when video signal applied

Thanks for the suggestion. I've tried just about every resolution under the sun. 1280 x 1024 is it's native resolution I believe, and this gets displayed in the menu. Some resolutions / refresh rates cause the power LED to blink, but apart from that all give the same result - black screen.
I've fixed a couple of monitors in the past where the power/inverter board has been the problem, but assuming the power board is ok and it's the video board that is at fault, does this mean it's for the scrap heap ?

[PCBONEZ]

Re: Philips 170S4 goes blank when video signal applied

Depends on what's wrong with the video board.
.

[redart]

Re: Philips 170S4 goes blank when video signal applied

Depends on what's wrong with the video board.
.

Thanks PCBONEZ I guess my inference was that there's not much to fix on a video board....well not this one anyway. Pic attached, sorry about the poor quality. About the only thing up for replacement to my mind would be the 8 pin DIP. Not sure what this does though. Any ideas ?.

[PCBONEZ]

Re: Philips 170S4 goes blank when video signal applied

SMD caps go bad too. They just aren't as much 'fun' as radials.

Have you reseated the ribbon cables?
They can develop bad contact in the sockets.

Have you checked that all the voltages are getting to the board?
.

[redart]

Re: Philips 170S4 goes blank when video signal applied

Well none of the SMD caps are bulging
Ribbon cables have been checked. Voltages going to the board are as follows... (see attached circuit diagram).
1, 2, 11, & 12 have 3.2V. 13 has 0.1V (brightness!), and 7 has 11.8V.
Not sure what the voltages should be apart from the 3.3 and 12. Should the brightness be higher?.

Stop the press ! Have just noticed that in the on-screen menu, the brightness and contrast values are reading -1, and wont respond to the buttons on the panel control board. The arrows next to their bar graphs blink when the buttons are pressed, but the graph and values remain at -1. Could this be significant ?.

[PlainBill]

Re: Philips 170S4 goes blank when video signal applied

Well none of the SMD caps are bulging
Ribbon cables have been checked. Voltages going to the board are as follows... (see attached circuit diagram).
1, 2, 11, & 12 have 3.2V. 13 has 0.1V (brightness!), and 7 has 11.8V.
Not sure what the voltages should be apart from the 3.3 and 12. Should the brightness be higher?.

Stop the press ! Have just noticed that in the on-screen menu, the brightness and contrast values are reading -1, and wont respond to the buttons on the panel control board. The arrows next to their bar graphs blink when the buttons are pressed, but the graph and values remain at -1. Could this be significant ?.

Yes. You probably have a corrupted user EEPROM. Google the model number of the monitor and reset for instructions on resetting it to default values.

PlainBill

[redart]

Re: Philips 170S4 goes blank when video signal applied

Yes. You probably have a corrupted user EEPROM. Google the model number of the monitor and reset for instructions on resetting it to default values.

PlainBill

The on screen menu has a "Reset to Factory Settings" option which I've already tried. Is this what you mean or are you talking about flashing the EEPROM ?.
I Google'd 170S4 reset and got a few pages that talk about this but none that explain how it can be done on a monitor. I presume the EEPROM is the 8 pin DIP next to the control board ribbon cable. It's an ATMEL 24C16A by the looks of it (very faint writing). Would replacing this with a blank equivalent work ?.

[PlainBill]

Re: Philips 170S4 goes blank when video signal applied

The on screen menu has a "Reset to Factory Settings" option which I've already tried. Is this what you mean or are you talking about flashing the EEPROM ?.
I Google'd 170S4 reset and got a few pages that talk about this but none that explain how it can be done on a monitor. I presume the EEPROM is the 8 pin DIP next to the control board ribbon cable. It's an ATMEL 24C16A by the looks of it (very faint writing). Would replacing this with a blank equivalent work ?.

Usually you hold down several of the front panel buttons while plugging in AC power to the monitor. Replacing the IC itself is another way to accomplish this. An Atmel 24C16 sounds like the right part.

PlainBill

[redart]

Re: Philips 170S4 goes blank when video signal applied

Usually you hold down several of the front panel buttons while plugging in AC power to the monitor. Replacing the IC itself is another way to accomplish this. An Atmel 24C16 sounds like the right part.

PlainBill

Thanks PlainBill. Have searched the net and can't find anything on doing a hard reset for this monitor. All I have is the OSD/Menu reset option, which has no effect.
I read somewhere else that installing a new, blank eeprom might not work, as it wont have any of the settings on it that the monitor needs. I tried starting the monitor without the eeprom and it wouldn't turn on at all. Is it just a case of try the blank and hope that it works ?.

[PlainBill]

Re: Philips 170S4 goes blank when video signal applied

Thanks PlainBill. Have searched the net and can't find anything on doing a hard reset for this monitor. All I have is the OSD/Menu reset option, which has no effect.
I read somewhere else that installing a new, blank eeprom might not work, as it wont have any of the settings on it that the monitor needs. I tried starting the monitor without the eeprom and it wouldn't turn on at all. Is it just a case of try the blank and hope that it works ?.

That's about the only option, but it doesn't look promising. There are at least two schemes I've seen used. One has the program memory in the main control chip, and user (configuration) data in a serial eeprom. On those the contents of the serial eeprom are read at power up and checked for corruption. On others there are two serial eeproms, one containing the firmware and some user data, the other containing user data. In the cases I've heard of with a single serial eeprom, the monitor will work without the IC, but settings cannot be saved. This is of course at the whim of the programmer.

PlainBill

[voxer]

Re: Philips 170S4 goes blank when video signal applied

@redart
I encountered the same problem with my Philips 170S4FG and was wondering if you managed to find a solution.

PS. The EEPROM in my set is 24C16W6 (ST Microelectronics)