Philips 190/B6 Monitor OSD Fault.

[banger]

Hi all newbie to this board here. Been having some problems with my Philips 190/B6 and the OSD intermittently flashing on and off. But I'm very rusty so need some help in diagnosing the problem.

This is the second monitor with a similar fault, first being replaced under warranty, but second is now out of warranty.

Fault appears to be as if the "OK/OSD" button is being pressed bringing up the OSD on screen sometimes momentarily then going off.

I've already had the monitor apart and cleaned the control board, which cured for 3 months then the problem came back. I have just replaced the tactile switch for the OSD button, and again one day in this seems to have cured the problem for now. Next day it flashed up again so replaced the Up, Down switches too. I think the line is connected to a schmitt trigger according to my searches for the CPU and a register which provides an interrupt to display the OSD but don't understand why it is self displaying. Think the CPU is 6502 so it might be possible in code to ignore the register for the buttons in the program but that's not an ideal solution.

But after removing the old switches - testing with an ohm meter shows the switch completely open circuit so I am doubting my current fix.

There appears to be three switches attached to one line, OSD/OK, UP and DOWN, each with a resistor of 47k, 10k and 1k0 respectively, pulling the line down when switch is pressed.

Can anyone point me in the right direction as where to look/test next ?

The service manual for the monitor including schematic can be found at
https://cdn.badcaps-static.com/pdfs/...149c139919.pdf

Sorry for long post and thanks in advance.

[banger]

Re: Philips 190/B6 Monitor OSD Fault.

Well so far so good. Replacing the three switches and cleaning the back of the board where the spark gaps are seems to have cured it for now. Have started a database of fail dates and fixes applied, fingers crossed, may have to repeat the cleaning at some stage. Next is to look at the caps on the scaler board see if any are bulging and possibly the power supply just in case the PSU is rippling and causing the register to get data. Feel free to shoot down my theories.

[kc8adu]

Re: Philips 190/B6 Monitor OSD Fault.

do you spray glass cleaner directly on the screen?
it runs inside and causes the problem you are having.
phillips seems to design stuff to be vulnerable to this.
fixed a ton of their tv's for this.

[banger]

Re: Philips 190/B6 Monitor OSD Fault.

Good thinking Batman, but I use screen alchohol wipes to clean the screen and they have very little fluid.

Previous monitor (warranty) failed with symptoms as if all keys were being pressed ie. volume, brightness and OK button after 2 and a half years of use. Interestingly this monitor has had about 2 and half years (bit more) since it's production in January 2006 which is stored in the NVRAM of the monitor. Also the running hours of the monitor in factory settings is 4084 hours. Out of 50,000 hours MTBF that isn't much.

I'm still trying to work out if it's PSU, Scaler board, keyboard/switches or temperature/humidity related. It's cured for the moment but temperature has really dropped, it was warmish when it happened, anyway fingers crossed.

Tim