STONE capacitors... suck. Badly.
Just today a neighbor of mine came in with a monitor he got for very cheap. It was one of those 12v powered things. Likom HD17A i think it was. It did not come with a power supply so he asked me to test it. Of course, it didn't work. Power LED would blink orange continuously and there was a ticking sound along with a slight flickering of the screen (lamps didn't power up).
2 bad NKCON caps on the inverter. Btw the inverter was using a TL494... Swapped out, still no change. All STONE caps on the combined PSU/logic board affair, in some weird short and fat form factor. All looked good... but as i started swapping them out for Rubycons, the monitor would power up, but only when the LCD ribbon wasn't connected.
At this point i was fed up with it and knew it isn't gonna work, so i just jammed the LCD ribbon in with the thing powered on. Surprise... it lit up. But with a full white screen. All power supplies tested good at this point btw.
The panel had an easily accessible driver board. Must be a really old panel. It had a big ACER chip on it, so i assume that's who made it. Probing around i found one of the three picofuses open. Jumpered it, and double surprise. No more white screen.
However, there were several lines on the screen that shouldn't have been there, the picture was slightly offset, and the thing continually cycled thru service patterns. No way of getting out of there. So not only did the STONE caps fail without bloating - they went bad enough to corrupt the EEPROM. I haven't checked the chip itself but i believe it was the 3.3v rail that did the damage, as it was a bit wiggly before recapping. If it was "a bit wiggly" on the multimeter i don't want to know how it would've looked on the scope.
This one was a lost cause.
2 bad NKCON caps on the inverter. Btw the inverter was using a TL494... Swapped out, still no change. All STONE caps on the combined PSU/logic board affair, in some weird short and fat form factor. All looked good... but as i started swapping them out for Rubycons, the monitor would power up, but only when the LCD ribbon wasn't connected.
At this point i was fed up with it and knew it isn't gonna work, so i just jammed the LCD ribbon in with the thing powered on. Surprise... it lit up. But with a full white screen. All power supplies tested good at this point btw.
The panel had an easily accessible driver board. Must be a really old panel. It had a big ACER chip on it, so i assume that's who made it. Probing around i found one of the three picofuses open. Jumpered it, and double surprise. No more white screen.
However, there were several lines on the screen that shouldn't have been there, the picture was slightly offset, and the thing continually cycled thru service patterns. No way of getting out of there. So not only did the STONE caps fail without bloating - they went bad enough to corrupt the EEPROM. I haven't checked the chip itself but i believe it was the 3.3v rail that did the damage, as it was a bit wiggly before recapping. If it was "a bit wiggly" on the multimeter i don't want to know how it would've looked on the scope.
This one was a lost cause.
