HP 1940 with a different inverter/power board

[Sygma6]

Hello all,

I am expanding in to fixing electronic devices on the component level for weekend/walking around cash and came upon this site looking for information on a LCD monitor I got for free. The power light turns green but there is no video or backlight.

The interesting thing is that the power/inverter board does not match up with the Benq ones that I have seen everywhere else on this site and the web at large. The number on the board is T50P057.

I am game for replacing the caps but I am having trouble finding a cross reference or even finding the original specs of what is installed there now. I've put as much information as I can figure out on the picture below. Any assistance would be most appreciated.

http://sygma6.net/pix/t50p057.png

[Bobdee]

Re: HP 1940 with a different inverter/power board

Hello Sygma6
Not the best place to be seen by the monitor gurus here
We post monitors in Troubleshooting Computer Displays
As you are going to recap those crapXtons, In general members recommend Panosonic FCs or FMs series
Dont bother with the big 100uf 450v its a general purpose cap, they very rarely fail

Suggestion if I may
If recap does not fix the monitor, take much better pictures of both sides of Board and post back in (Troubleshooting Computer Displays) lots of help there
Inform them of the caps you replaced
BTW that is strange board for hp 1940, I dont think its a Benq it may have been swapped by previous owner, only a thought

[Sygma6]

Re: HP 1940 with a different inverter/power board

I doubt it was replaced by the previous owner as the entire monitor was replaced when it went bad. My company had the 1940 under contract and it seems like such a nice monitor to let it go to waste. I will try to see if I can get a better picture and repost in the section you mentioned.

[Sygma6]

Re: HP 1940 with a different inverter/power board

I replaced the caps as marked in the picture and the backlight still does not turn on and there is no video but the light is green. I am thinking that the pico fuses have gone out so I am going to try those next. Any other suggestions?

http://sygma6.net/pix/t50p057.png

[Bobdee]

Re: HP 1940 with a different inverter/power board

A failed inverter pico fuse would make sense, but I dont see one
Picture of the other side of this Inverter/PSupply is a must have
Can you confirm that when you turn the monitor on only the green light comes on and nothing else happens, and the same when you turn on/off again ??? (no quick flash of B/lights or no input signal box ect)

[EGuevarae]

Re: HP 1940 with a different inverter/power board

A failed inverter pico fuse would make sense, but I dont see one
Picture of the other side of this Inverter/PSupply is a must have
Can you confirm that when you turn the monitor on only the green light comes on and nothing else happens, and the same when you turn on/off again ??? (no quick flash of B/lights or no input signal box ect)

Agree. Post a pic of the underside of the board

[Sygma6]

Re: HP 1940 with a different inverter/power board

Here are some pictures of the underside. I don't have the proper equipment to get a good picture of the shiny bottom so I had to go at an angle and focus on half the board at a time due to depth of field issues with a point and shoot.

http://sygma6.net/pix/straighton.jpg
http://sygma6.net/pix/tophalf.jpg
http://sygma6.net/pix/bottomhalf.jpg

Again, thanks for the assistance. This is fun.

[Toasty]

Re: HP 1940 with a different inverter/power board

Turn it on and supply video input. Light is steady green?

If so, shine a flashlight on an angle on the front and see if there is video.

Set your voltmeter to its highest range DC (250v or better), hook the negative to the large filter cap negative leg, and see if you get any voltage across that cap. If you do, then keep the neg lead attached and carefully probe around on those exposed jumper wires on the topside. Stay clear of the tube transformer area(s) on the left. Check on several exposed component leads. If your getting readings in several areas, I don't think you've a fuse problem.

I'm thinking your back lights are shot. I'm also concerned about the large amount of discoloration of the board above the lower transformer only. It may be failed.

Toast

[Sygma6]

Re: HP 1940 with a different inverter/power board

Turn it on and supply video input. Light is steady green?

If so, shine a flashlight on an angle on the front and see if there is video.

That was one of the first things I tried. No video before or after replacing the capacitors.

Set your voltmeter to its highest range DC (250v or better), hook the negative to the large filter cap negative leg, and see if you get any voltage across that cap. If you do, then keep the neg lead attached and carefully probe around on those exposed jumper wires on the topside. Stay clear of the tube transformer area(s) on the left. Check on several exposed component leads. If your getting readings in several areas, I don't think you've a fuse problem.

I'm not quite sure what you mean by jumper wires. I had thought they were used after the fact for repairs and such. Are you referring to the solid wires on the top side like the ones at position 9810 and 9118 just to the left of the heatsink?

I'm thinking your back lights are shot. I'm also concerned about the large amount of discoloration of the board above the lower transformer only. It may be failed.

I'll check again and get some readings at the office today. If the transformer is blown how do I go about identifying it to find a replacement? I do not see anything in the way of markings on either of them unless they are on the underside.

[Bobdee]

Re: HP 1940 with a different inverter/power board

That discolouration is probably down to the 2 fets on underside of board (AOD442s) but no point going there yet when you have no video, I like to hold BRIGHT torch flat to screen and move it around to get best results
(Obviously connected to a running comp)
There maybe SMD fuses on underside of board, hard to see with these pics
Eguevarae will be the man to know where they are if any on there, he has done a lot of this type of board