I have a revision of this display with independent +12V PSU, a TDK inverter for 6 tubes and big signal board. After recap the PSU provides +12 V OK with 25 mV ripple, when it works, tubes light OK so inverter is also working.
Problem is than with signal board. First, when I am lucky, it powers up for the first try and shows image OK. But than if I turn it off, I won't get image when I turn it on again even though display seems to be operating, there is +5 V on inverter on/off pin (but 0 V on brightness pin).
Lately it just lights diodes for a while, than it switches to a state when only orange diode is on and the backlight is in operation. It seems to be a state when it has no input connected, but I have D-Sub plugged in all the time! And the worst, it does not react to power button at all, no matter how many times I press it.
The button is OK, cables as well - I can read drop of voltage from 5 V to 0 on one resistor near the pannel connector. I have replaced all 100uF caps and 10uF caps on the signal board, some of them were not in the best condition. Now only a few 22uF casp remain and soem bigger filtration ones (but these are OK). Can repalce the 22uF ones but I bet this is not the problem.
I've noticed the signal board gets some feed from the D-Sub, +5 V and there is some regulator to make 2,5 V from that.
Problem is than with signal board. First, when I am lucky, it powers up for the first try and shows image OK. But than if I turn it off, I won't get image when I turn it on again even though display seems to be operating, there is +5 V on inverter on/off pin (but 0 V on brightness pin).
Lately it just lights diodes for a while, than it switches to a state when only orange diode is on and the backlight is in operation. It seems to be a state when it has no input connected, but I have D-Sub plugged in all the time! And the worst, it does not react to power button at all, no matter how many times I press it.
The button is OK, cables as well - I can read drop of voltage from 5 V to 0 on one resistor near the pannel connector. I have replaced all 100uF caps and 10uF caps on the signal board, some of them were not in the best condition. Now only a few 22uF casp remain and soem bigger filtration ones (but these are OK). Can repalce the 22uF ones but I bet this is not the problem.
I've noticed the signal board gets some feed from the D-Sub, +5 V and there is some regulator to make 2,5 V from that.
Half of the computer problems is caused by bad contacts 
...
Comment