Help with a HP L1800

[mjsbv]

I've got a L1800 monitor by HP (D5065A) with some issues. It still works but lamps seem dim and has significant wavy horizontal lines moving verticly on screen. This is an older unit built in 99 and built like a tank. No cost reduction efforts in this baby. It has a backlight timer that says it has 27000 hours on it with 3000 left so I'd guess the lamps are about done for. But if it didn't have the lines would still be useable. I cracked it open and found no bulging or leaked caps just one little 4.7 uf with a red dot on top (don't know if thats a leak or not so I replaced it). Only other thing I found was one of the two inverter transformers seemed to have a clear goo all over the secondary end. Looks like hot melt but softer and spread around like it ran out of the transformer. Is this the winding insulation/potting comming out that would indicate its gone bad? Would a weak or bad transformer make the wavy lines? Didn't seem like it to me. I checked all the caps I could with out removing them for cap value and all seemed ok. I don't have a esr meter so perhaps there is a bad one in there. I've looked a little for replacement transformer but no luck yet. What do you think? Is it worth the effort to try to fix?

Thanks
Mark

[EGuevarae]

Re: Help with a HP L1800

if you give the brand/ series of the installed caps, perhaps someone can come with a suggestion (did you look up the caps in your board against the bad cap list in this site?)
I'm going to start a thread about a Proview 568 that has no bad caps on a visual inspection, but it delays to start on cold. Checking my notes, all the caps are su'scon (in the bad list), so maybe your problem is similar to mine.
Greets from SoCal.

[mjsbv]

Re: Help with a HP L1800

I spent a bit more time working on this thing and have found it seems to have two problems. One is the wigglely lines that angle across the screen at about 30 deg from horizontal and slowly scroll vertically and the other is one half of the inverter isn't working. It only lights one lamp and the same side works on the other lamp when I switch the lamps. Intrestingly the side that works is the one that had the goo all over it. There are several surface mount power transistors that I'll test. I think that explains the dim screen but not the lines.

I illuminated the screen with a flashlight with the inverter disconnected and the lines are still present. The inverter board only has 2 lytic caps (220uf-16V). I replaced both of them but it made no difference. The main board also has only 2 normal lytic caps that are 470uf-25v so I replaced them too but no difference. There are also about 6 surface mount caps that look like they might be lytics but in metal cans. They are 100uf-10V. I made a small effort to get one off the board but gave up when it didn't come off easy. This monitor uses a offboard brick powersupply that puts out 12v 5A. I'm going to rig up a replacement power source to see if the PS is the problem.

Any thoughts on what else I should test to figure this one out?

Thanks
mjsbv

[Scenic]

Re: Help with a HP L1800

hmm... sounds like my HP L1820 (18" 1280x1024)

if it looks like this one


and its power brick has a 4 pin connector, its probably the same thing internally..

i replaced _all_ caps on the "mainboard" in that LCD to fix it.
had to play around a bit because i couldn't find matching caps in the same size (this thing hat "Elite" and "Lelon" caps all over it )
so i ended up putting a few caps lying flat on the pcb and some of them off-board connected with wires, because it was almost impossible to find good caps with the same physical size as the original ones..

a pic of those original crapcaps (all dried out)
that rubycon on the right is just for size comparison..
http://bambooz.pytalhost.net/badcaps..._mini-caps.jpg

i hope i can find the pics i made back then when i was fixing this thing..
can't remember where i put them lol

[mjsbv]

Re: Help with a HP L1800

My monitor looks pretty different than yours. It also only has a simple 12v power brick with coaxiel plug. The four caps that were labled were samaxon or something like that. The inverter board says samsung on it. The main board has no name at all which is unusual for an HP designed board (if it is).

I used the o-scope to check out the sm al caps on the main board under power and found 2 with a little ripple. When I replaced these the wavy lines went away, yea, but when started cold the next day were back and worse than before. The caps I used were general purpose ones I had laying about. After a few minuits of warm up the lines went away so I hope that quality replacements will work better. I also finally realized that the inverter board has two 2A sm fuses and one was blown. The other lamp worked once that was replaced. Will have to let it burn in to see if it blows again or if replacing the caps fixes the overload.

mjsbv

[EGuevarae]

Re: Help with a HP L1800

Did you check caps (if any) on the inverter?

[mjsbv]

Re: Help with a HP L1800

I replaced the two caps on the inverter board.