VHO VT17w71 Display issue blinking PLED

[alexanna]

I started working on this monitor today. The monitor powered on, I am not sure what to call it washed out display very light colors on the display.
Running the monitor after about 4 minutes I noticed the PLED start to flash and the back lights trying to come on ,dimly flashing at the same rate as the PLED .
When the PLED was flashing I noticed the 12volt and 5voltages briefly going away and then coming back.
I replaced a 50v 4.7 uf cap and a 35v 100uf cap that were probably for the start and run circuits.
The blinking of the PLED stopped and back lights worked correctly but I still had display problems. I was lucky enough to have another monitor that was exactly the same, I substituted the logic board from the good monitor and it had no effect on the display problem. Next I tried replacing the 30 pin cable from the logic board to the LCD and the display problems went away.
I cleaned and reinstalled the original 30 pin cable and reinstalled it to the panel and the display issues were resolved. Originally the cable was glued to where it attached to display so I don't think it was loose. And I did replace all the remaining capacitors.
Al.

[alexanna]

Re: VHO VT17w71 Display issue blinking PLED

Wow this inverter circuitry is different
I have several of these monitors, this one had a green power LED and I could see an image with a flash light but there was no back light activity at all.
After opening the monitor up it had obviously bloated capacitors and the inverter fuse was good. After the recap I still had nothing from the back lights. I took a close look at the inverter section and it's different than any I have seen, I don't see the normal inverter controller that I am used to seeing.
Luckily for some reason I hooked my test bulbs, and the bulbs lit up .This particular monitors back lights will work with up to two bulbs not working as long as there is one working on each side of the inverter, it doesn't matter which connector.
Al.

[PlainBill]

Re: VHO VT17w71 Display issue blinking PLED

Wow this inverter circuitry is different
I have several of these monitors, this one had a green power LED and I could see an image with a flash light but there was no back light activity at all.
After opening the monitor up it had obviously bloated capacitors and the inverter fuse was good. After the recap I still had nothing from the back lights. I took a close look at the inverter section and it's different than any I have seen, I don't see the normal inverter controller that I am used to seeing.
Luckily for some reason I hooked my test bulbs, and the bulbs lit up .This particular monitors back lights will work with up to two bulbs not working as long as there is one working on each side of the inverter, it doesn't matter which connector.
Al.

It's a very sparse design, all right. Ref: The attached picture. The area circled in red (and the components in the same area on the top) are the Royer oscillators. The areas circled in blue are the current sense circuitry. And the area circled in yellow is the inverter controller. No OVP on this guy.

PlainBill