Hp 1940 flicker

[selldoor]

Re: Hp 1940 flicker

So far so good then- whilst budm has referred to the grey caps and his knowledge is far superior to mine, it is the first time I have noticed anyone make that suggestion. Unless you have an esr meter or cap tester I dont think you can test them, you can look for bulges or leakage, but I have never known anyone replace this type of caps.
Heat is a monitor killer so additional ventilation will certainly do no harm.

[budm]

Re: Hp 1940 flicker

Please read this thread about the tuning caps used in Royer Oscillator circuits:
https://www.badcaps.net/forum/showthread.php?t=19878
As Jasgriff found out after damaged new transistors he had replaced.

[Hunt]

Re: Hp 1940 flicker

Heat is a monitor killer so additional ventilation will certainly do no harm.

There is a comment somewhere that people have fitted fans to monitors.

Is there a suitable place on the monitor to pull 12v or even 9v (make less noise) DC to run a fan off?

[selldoor]

Re: Hp 1940 flicker

I am sure there are places where you can pull 12 v or even 5v off the power supply but wonder if it would be too much for it. I would suggest a usb powered fan run off the pc as your not likeley to have one on without the other. If you dont want to tie up a usb you could run 12 v or 5v off a molex
connector inside the pc

[Hunt]

Re: Hp 1940 flicker

Well it has been nearly a week since I re-soldered all the underside joints in the area of the four transformers and near all the discoloured section of the board.

No flickering yet and I believe the use of the monitor is reprehensive of when it was faulty.

My only concern now is the comment above about... "Also check the two rectangular body gray caps for value and leakage otherwise you may blow up your transistors."
How do I test for the above?

I'm also wondering if drilling more holes in the metal cover of the same size (finger safe) as already exist but on the adjacent side to aid cooling?

Then putting more finger safe holes in the plastic back cover?

Thanks for your help so far people.

I have fully reassembled the repaired monitor and have used it in a three-monitor system now for a week or more and I am very pleased with the results.

I have not added a fan. However, I have provided more cooling holes to the metal case and to the plastic back cover.
Pictures attached.

P.S. As I write this, I'm sure the monitor made a click. Any ideas what this could be?

[ratedK]

Re: Hp 1940 flicker

I opened up my HP L1940T expecting to find a bad cap but it was nowhere to be found, everything I could test read as it should. Thank you badcaps

Simply refreshing the solder joints worked like a charm. My board didn't indicate BenQ, but the same solution worked for me just the same.

https://www.badcaps.net/forum/images/smilies/fruit.gif

Since I have a pair for dual screen setup I'm thankful that I didn't have to replace two screens. Most Awesome.

[Hunt]

Re: Hp 1940 flicker

My HP 1940 lasted till now with only the odd flicker perhaps once a week. I just went blank and came back up ok.

Now though it has a constant flicker with the green light going on and off.

I have done a re-solder just in case it was a simple problem again but it has made no difference so I think the monitor has had its day.

3 years extra life is very good thanks to this forum

Problem is they do not seem make the old format monitors now.

Of to see what is available secondhand...

[stj]

Re: Hp 1940 flicker

you give up to easy!
see if it powers up with the cfl tubes unplugged.
these HP's overdrive the tubes - i'v had one with one of the lamps cracked from heat.