Replacement inverter board for HP 1940

[archie456]

Hi,

I have a HP 1940 LCD screen which flashes on and off.

I've checked the board and resoldered new caps on it - but it still keeps flashing the picture on and off.

I've given up trying to fix it, does anyone know where I can buy a replacement board.

The board is a BENQ 48.L1G02.A00

Thanks.

[Krankshaft]

Re: Replacement inverter board for HP 1940

Replacement for that board would be tough.

Did you replace the C5707 transistors and the pico fuse?

That's the common problem with these boards.

[archie456]

Re: Replacement inverter board for HP 1940

Replacement for that board would be tough.

Did you replace the C5707 transistors and the pico fuse?

That's the common problem with these boards.

Thanks for your reply!

I'm a bit of a noobie at electronics...

... is the C5707 transistor the thing which is screwed to the heat sink?

what does the Pico fuse look like?

I've attached a pic of the board!

[Bobdee]

Re: Replacement inverter board for HP 1940

A french link here but I am not sure if its for board or schematic

http://translate.google.co.uk/transl...1G02%26hl%3Den

its not guarenteed that a new board will fix it as you may have a CCFL problem, as Krankshaft said there is a common problem with these boards

[archie456]

Re: Replacement inverter board for HP 1940

Ah ha! Found the C5070 transistors - theres 4 of them.

(Haven't found the pico fuse yet though).

Are the C5070 transistors something you can get from any component shop - like RS?

[archie456]

Re: Replacement inverter board for HP 1940

A french link here but I am not sure if its for board or schematic

http://translate.google.co.uk/transl...1G02%26hl%3Den

its not guarenteed that a new board will fix it as you may have a CCFL problem, as Krankshaft said there is a common problem with these boards

Thanks Bobdee. I did actually find that site, but didn't try to buy one as I couldn't speak French (though I've found someone at work who does - but might try to replace the transistors first to see what happens)

[Bobdee]

Re: Replacement inverter board for HP 1940

Thanks Bobdee. I did actually find that site, but didn't try to buy one as I couldn't speak French (though I've found someone at work who does - but might try to replace the transistors first to see what happens)

Good , easy fix

fuse yellow just above large transformer

c5707 =2sc5707 plenty on ebay

[archie456]

Re: Replacement inverter board for HP 1940

I've just ebayed 4!!

Thanks for your help!

[archie456]

Re: Replacement inverter board for HP 1940

Suburb!! I replaced the c5707 transistors and the monitor work again!!

I'm well pleased!

Thanks for your assistance - you were a great help!! Especially as this is the second time in my life which I have picked up a soldering iron!

Great forum.

[archie456]

Re: Replacement inverter board for HP 1940

Bugger.

Just when I thought it was fixed it went again.

It lasted about a week of perfect usage, and then pop - same problem again.

It happened when I was turning it on.

The C5707 transistors were cheap enough to replace again, but I'm now thinking its something causing them to go.

Any of you chaps know what can cause them to go.

Also, is it possible to but 'better ones' which are more resilient?

[Bobdee]

Re: Replacement inverter board for HP 1940

Bugger.

Just when I thought it was fixed it went again.

It lasted about a week of perfect usage, and then pop - same problem again.

It happened when I was turning it on.

The C5707 transistors were cheap enough to replace again, but I'm now thinking its something causing them to go.

Any of you chaps know what can cause them to go.

Also, is it possible to but 'better ones' which are more resilient?

Hello again
This happens often if you have not resoldered the 4 inverter transformers also you need to check the rest of the solder joints on the board paying particular attention to anything on heatsinks and the 2 mosfets FU9024N (they look like the transistors)
best use a good magnifyig glass 8 or 10 X magnification
The 2SC5707s are the best ones for this inverter, plenty of recomendations for them from people like DAVMAX and alike, thats good enough for me

bob

EDIT probably only one transistor has gone and the fuse again

bob

[EGuevarae]

Re: Replacement inverter board for HP 1940

Hello again
This happens often if you have not resoldered the 4 inverter transformers also you need to check the rest of the solder joints on the board paying particular attention to anything on heatsinks and the 2 mosfets FU9024N (they look like the transistors)
best use a good magnifyig glass 8 or 10 X magnification
The 2SC5707s are the best ones for this inverter, plenty of recomendations for them from people like DAVMAX and alike, thats good enough for me

bob

EDIT probably only one transistor has gone and the fuse again

bob

I agree with Bob. Resolder all the transformer points. Or you'll be swapping the Qs again in no time ...

[dmbj]

Re: Replacement inverter board for HP 1940

These boards just drive me crazy. I have 2 right now. total recap with good caps from the good cap list. replaced all 4 c5707 with tested good new ones (even though one all 4 on one board tested good out of circut the other 4 here bad) re-soldered all points on all transformers, all transistors on heat syncs and anything that even looked suspect. now one still comes up for 2 seconds and the other just has a white screen now. both have a good pico fuse.

FRUSTRATED

Consumer grade monitors are so much easier than these things. The bummer for me is there is a guy dumping these things on me for $10 non working form some hospital and the other ones with other inverter boards are a pita also. not a one of them ever had a puffy cap. they all just get the 2 sec flash. if anyone needs a good lcd for the 1740's let me know i have a crap load of them

[Bobdee]

Re: Replacement inverter board for HP 1940

These boards just drive me crazy. I have 2 right now. total recap with good caps from the good cap list. replaced all 4 c5707 with tested good new ones (even though one all 4 on one board tested good out of circut the other 4 here bad) re-soldered all points on all transformers, all transistors on heat syncs and anything that even looked suspect. now one still comes up for 2 seconds and the other just has a white screen now. both have a good pico fuse.

Possibly a bad CCFL on the one
Also the white screen one can be a tiny fuse on panel,(or someone left a connector off like I have done in the past)

[dmbj]

Re: Replacement inverter board for HP 1940

Possibly a bad CCFL on the one
Also the white screen one can be a tiny fuse on panel,(or someone left a connector off like I have done in the past)

I can swap the 2 boards from one panel to the other or mix and match the 4 board in any combination with the 2 panels and there respective ccfl's and the problems follows the inverter boards. So as far as i can tell the bulbs are good in both panels, and the lcds are both good.

The good news is i just got an email from a free cycler that i can pick up an unknown brand 19"er that just went bad the other day for FREE and its just done the road from home.

[EGuevarae]

Re: Replacement inverter board for HP 1940

Possibly a bad CCFL on the one
Also the white screen one can be a tiny fuse on panel,(or someone left a connector off like I have done in the past)

I agree. The input fuse is blown almost for sure on the white screen panel.

[Bobdee]

Re: Replacement inverter board for HP 1940

I agree. The input fuse is blown almost for sure on the white screen panel.

Hello Eguevarae
I think we are both wrong going by his last post,I think he is saying his white screen follows the inverter P/S board when fitted onto the other screen so it looks like P/S on that board,
and still inverter on other board because those black screen symptoms follow that board (I think) thats what he says in his last post to my understanding, whats your thoughts on it
bob

[EGuevarae]

Re: Replacement inverter board for HP 1940

Hello Eguevarae
I think we are both wrong going by his last post,I think he is saying his white screen follows the inverter P/S board when fitted onto the other screen so it looks like P/S on that board,
and still inverter on other board because those black screen symptoms follow that board (I think) thats what he says in his last post to my understanding, whats your thoughts on it
bob

Kinda confusing. But the blank screen is either a bad LCD panel (I've seen it on Hanns-G HU171 : I have two dead ones), a bad fuse on the LCD panel or a bad 5v output (which goes into the LCD panel) from the logic board (I have seen this before too. It was related to a bad 5v rail on power supplies) to the LCD panel.

[Bobdee]

Re: Replacement inverter board for HP 1940

Kinda confusing. But the blank screen is either a bad LCD panel (I've seen it on Hanns-G HU171 : I have two dead ones), a bad fuse on the LCD panel or a bad 5v output (which goes into the LCD panel) from the logic board (I have seen this before too. It was related to a bad 5v rail on power supplies) to the LCD panel.

Hello again
Thanks for info
So the bad 5v rail can start on the P/Supply side to give dmbj this white screen??? (thats my guess but unsure)
bob

[EGuevarae]

Re: Replacement inverter board for HP 1940

Hello again
Thanks for info
So the bad 5v rail can start on the P/Supply side to give dmbj this white screen??? (thats my guess but unsure)
bob

Yes.Seen this once. But as soon as the PSU was recaped and the 5v was stable, the panel came to life. It was a Proview/MAG 700P, as far as I can remember.