LCD wrong viewing angle Sony Walkman

[dredd]

Hello.

I bought Sony Walkman to restore, WM-FX822. I still waiting on rubber band, but radio works. Now problem is, I can see LCD screen in good contrast only looking at it at 45 degrees down from vertical, and still good all the way down to 90 deg (when its on the table and I'm on the battery side). When i move up to vertical view (0 deg) it fades to nothing.

I tried feeding it from lab PSU at 1.5V, nothing changed.

I attached service manual, IC702 is LCD driver chip. Whats can be done here, please?

Thanks!

[dredd]

There is numbers on IC702 pins on the diagram, I think its ref voltages, I'm yet to check it. But I suspect complex waveforms there, from what I read on multiplexed LCD drivers, ones with more than one Common pin from the glass (this has four, there is pins description table in the doco).

[GLouie]

Just guessing, could there possibly be a polarizing film over the display that is backwards, or missing?

[dredd]

Just guessing, could there possibly be a polarizing film over the display that is backwards, or missing?

Seems unlikely, how could this happen. I'm waiting on solder sucker and will lift the pcb tomorrow. There is "zebra strip", conductive rubber thing inside LCD assembly, I plan to open the assembly.

[dredd]

Well, cleaning the conductive rubber strip inside LCD assy did not help

[R.J.]

Does the walkman react on any button?

Please check C701 in the reset circuit and the other components around.

[dredd]

Does the walkman react on any button?
Please check C701 in the reset circuit and the other components around.

Yes, Walkman if fully operational. Will do C701! Sorry for long delay, I used email I don't check, changed now

[R.J.]

The display is directly driven by IC702.
This is a microprocessor and need a oscillator to operate so also check R724 (470k) or the pins with an oscilloscope.There has to be a smal signal (sinus/square) on both sides of this resistor.
The reset signal from Q701 (collector) should be 0V and on pin 27 of IC702