HP L1702 goes on and off

[dvorav]

Re: HP L1702 goes on and off

Yes, the monitor all goes off. And it couldn't be turned on for a while (unless you unplug it and pug it in again with some delay). Seems strange.
And also that buzzing noise, can't determine right direction, but it seem it is going from PSU board (maybe even from the small green board on it).
Any clues?

[Qwertyco]

Re: HP L1702 goes on and off

I have a 2005 L1702 with the same problems, but it seems to have a different inverter board to all your photo's.
It was flickering on for a few seconds, then losing the backlight.
Green light is on, and the image can be seen shining a bright light on the screen.
I changed all 13 caps, and now I don't even get the initial flickering!
Image is still visable, so just no backlights at all now.

What do I do next?

[PlainBill]

Re: HP L1702 goes on and off

I have a 2005 L1702 with the same problems, but it seems to have a different inverter board to all your photo's.
It was flickering on for a few seconds, then losing the backlight.
Green light is on, and the image can be seen shining a bright light on the screen.
I changed all 13 caps, and now I don't even get the initial flickering!
Image is still visable, so just no backlights at all now.

What do I do next?

Post good pictures of the power supply and inverter, both top and bottom. You will have to check the fuses.

PlainBill

[Qwertyco]

Re: HP L1702 goes on and off

Post good pictures of the power supply and inverter. . . . .
PlainBill

Thanks PlainBill,
Can't seem to upload to the forum, so they are on photobucket,
Here you are:
Pic 1
Pic 2
Pic 3
Pic 4
The main fuse just below the power cable is Ok. I can't see another fuse anywhere on either board!

Thanks,
Mike Q

[Bobdee]

Re: HP L1702 goes on and off

Top of board to the left of 1st picture behind pair of caps, looks like 3 Amp fuse
Those new caps on inverter look like Jamicon KT, if they are is the esr low enough for inverter???

[PlainBill]

Re: HP L1702 goes on and off

Thanks PlainBill,
Can't seem to upload to the forum, so they are on photobucket,
Here you are:
Pic 1
Pic 2
Pic 3
Pic 4
The main fuse just below the power cable is Ok. I can't see another fuse anywhere on either board!

Thanks,
Mike Q

Oops, Bobdee caught it!! Well done.

PlainBill

[Qwertyco]

Re: HP L1702 goes on and off

Thanks for the quick response Guys!

I did wonder what that component was, it has a 'J801' number. (Jumper?)
I'll check it tonight.
If it has blown, can I replace it with another type of 'off board' fuse, as I don't know where I'd find one of those?

The new Caps came from here:
Caps LINK
I'm afraid I don't know what ESR means!

Please be aware that I'm just handy at soldering and replacing things.
I have no electronics background, (in fact I'm an offshore piping engineer!)

[PCBONEZ]

Re: HP L1702 goes on and off

ESR = Equivalent Series Resistance.
Resistance is for DC.
The same property (resistance is not correct word for AC) in caps for AC is the sum of the effects of Xc and ESR.

As the AC frequency goes up, Xc goes up and ESR goes down.

ESR is measured [Rated] at 100 kHz where Xc is nearly zero.

100 kHz is close to the frequency of the noise created by the SMPS that these caps are there to filter out so ESR is what we look at to know how effective a cap will be at filtering out that noise.
.

[Bobdee]

Re: HP L1702 goes on and off

ESR = Equivalent Series Resistance.
Resistance is for DC.
The same property (resistance is not correct word for AC) in caps for AC is the sum of the effects of Xc and ESR.

As the AC frequency goes up, Xc goes up and ESR goes down.

ESR is measured [Rated] at 100 kHz where Xc is nearly zero.

100 kHz is close to the frequency of the noise created by the SMPS that these caps are there to filter out so ESR is what we look at to know how effective a cap will be at filtering out that noise.
.

Hello PCBONEZ
Can you help Me and Qwertyco out with this dilemma, I use these Jamicon TK from MAPLINS in Monitor P/SUPPLY without problems but never in the Inverter, due to reading members advice that you only use good Quality low ESR caps in Inverters, the D/Sheet for these caps is as follows



Can these work in the Inverter at all ???
If so any guesses as to how long they would last given that they are rated as Standard G/Purpose caps

I know a little about ESR and caps only what I have read in Forum but dont fully understand it,
Could this be Qwertyco problem ???
Would appreciate any info you can give.
Many Thanks
bob

[Bobdee]

Re: HP L1702 goes on and off

Thanks for the quick response Guys!

I did wonder what that component was, it has a 'J801' number. (Jumper?)
I'll check it tonight.
If it has blown, can I replace it with another type of 'off board' fuse, as I don't know where I'd find one of those?

The new Caps came from here:
Caps LINK
I'm afraid I don't know what ESR means!

Please be aware that I'm just handy at soldering and replacing things.
I have no electronics background, (in fact I'm an offshore piping engineer!)

Hi Qwertyco
I doubt if that fuse is your probem, you say you still see image if that is so then that fuse will be ok due to it being input fuse for other board, cant see inverter fuse anywhere, was wondering if there is a fuse under that glue gunge lower down the board between those 2 caps or is it just a jumper
Plainbill and PCBONEZ will see you right, in the meantime check your solder joints for ring cracks with a good magnifying glass on the inverter transformers and anything on a heatsink resolder if needed
bob

[Qwertyco]

Re: HP L1702 goes on and off

Thanks Bobdee,
I'll get my Lidl magnifying glass and Aldi soldering iron out this weekend.

There's nothing under any of the white globs, I removed it all after I took the photo's.

I seem to have made this worse by changing the caps!
At least I got 2 seconds of flickering image before!

Is it usual to have so many different boards in one model of monitor?
I've seen pictures of 3 different versions of the power/inverter in an HP L1702 so far!

[Bobdee]

Re: HP L1702 goes on and off

Thanks Bobdee,
I'll get my Lidl magnifying glass and Aldi soldering iron out this weekend.

There's nothing under any of the white globs, I removed it all after I took the photo's.

I seem to have made this worse by changing the caps!
At least I got 2 seconds of flickering image before!

Is it usual to have so many different boards in one model of monitor?
I've seen pictures of 3 different versions of the power/inverter in an HP L1702 so far!

Hello again
It may seem worse but its not realy, it is your inverter that has the problem and its never that hard to put it right, transistors, or soldering, fuses ect even CCFLs sometimes, never had a transformer die on me yet and I have a lot of repaired monitors under my belt,so they should be ok with luck.
But those jamicon TK caps on inverter may be your problem,I do say May (I dont know for certain myself) I am eager to find out myself on that one,have to wait for PCBONEZ to reply or another helpful member even, but PCB certainly knows his caps

No its not that unusual for more than one board be used in the same monitor, or for that matter you sometimes find the same boards in other monitors
Thats why some members put their board No in there post so as it can be crossed referenced with search box,so that if you cant find info on your particular monitor then you may find info on another monitor that uses your board by searching your board No (hope that made sense)
bob

[PCBONEZ]

Re: HP L1702 goes on and off

Hello PCBONEZ
Can you help Me and Qwertyco out with this dilemma, I use these Jamicon TK from MAPLINS in Monitor P/SUPPLY without problems but never in the Inverter, due to reading members advice that you only use good Quality low ESR caps in Inverters, the D/Sheet for these caps is as follows



Can these work in the Inverter at all ???
If so any guesses as to how long they would last given that they are rated as Standard G/Purpose caps

Yes the Jamicon TK are general purpose. General purpose caps often don't even have ESR shown in data tables and Jamicon TK does not show it.

The ~best~ thing to do is look up specs of old caps and then at least match those.
I say that because, where one design uses two middle grade caps, another design might use one high grade cap to do the same thing.

-Usually- LCD screens use caps about the grade of Panasonic FC but -occasionally- they use caps closer to Panasonic FM.
If you don't know what the old caps were for sure it is best to "fail up" and use something like FM or better.

Xc + ESR is Impedance.
Some data tables will say Impedance and some will say ESR.
The reason is at 100kHz [or occasionally 120kHz] the Xc is almost zero and so at the frequency used in the data tables ESR = Impedance almost exactly.
Some companies use 120kHz instead of 100kHz in their data sheets.

I attached tables for FC and FM.
Look at 1000uF 6.3v in both tables and compare.

ESR is given as Ohms at 100kHz and at 20°C
Higher Ripple is given as Milliamps at 100kHz and at 105°C
[ Some data sheets give ESR in Milliohms instead of Ohms. ]

ESR and Ripple are ratings for AC characteristics.
If it was DC instead then ESR would be Resistance and Ripple Current would be Amps.
-
ESR tells you how easy it is for the cap to pass Ripple.
[Less ESR is better]
The Ripple Current rating tells you how much it can pass without overheating.
[More Ripple Current is better.]
.

[PCBONEZ]

Re: HP L1702 goes on and off

What are the old caps?
I have data sheets for all sorts of hard to find caps.

[Qwertyco]

Re: HP L1702 goes on and off

Big thanks for all this advice!
I'll check the old caps tonight, non of them showed any sign if distress, but I changed them all anyway.

Where can we buy small quantity good quality caps in the UK?
Maplins is my only source (but it's turned into a toy shop these days!)

. . . and for future search purposes, the inverter board is a PTB-1569 dated 10/21/'04
and number 6832156900-01

[PCBONEZ]

Re: HP L1702 goes on and off

This guide is pretty good. [Site owner is moderator here.]
http://www.capacitorlab.com/where-to...tors/index.htm
.

[EGuevarae]

Re: HP L1702 goes on and off

Is it usual to have so many different boards in one model of monitor?
I've seen pictures of 3 different versions of the power/inverter in an HP L1702 so far!

As usual as having one PSU/Inv board in many different LCD brands/models.

[Qwertyco]

Re: HP L1702 goes on and off

Typical old caps I removed are marked:

CapXon
470uF 35v
KM 105c
C514
VENT

[severach]

Re: HP L1702 goes on and off

ESR tables aren't necessary. Ripple current tables are sufficient.

Jamicon TK are low ESR caps. They are used in SMPS power supplies by many manufacturers and are suitable for LCD SMPS where quality and long life are not an issue. I have some used Jamicon here with ESR that have similar ESR to good brands:

Jamicon TK 2200uf 10v 0.02 ESR
Jamicon TK 2200uf 16v 0.04 ESR
Jamicon TK 1000uf 10v 0.08 ESR

It would be nice to have better caps but the Jamicon probably aren't the problem.

[Bobdee]

Re: HP L1702 goes on and off

ESR tables aren't necessary. Ripple current tables are sufficient.

Jamicon TK are low ESR caps. They are used in SMPS power supplies by many manufacturers and are suitable for LCD SMPS where quality and long life are not an issue. I have some used Jamicon here with ESR that have similar ESR to good brands:

Jamicon TK 2200uf 10v 0.02 ESR
Jamicon TK 2200uf 16v 0.04 ESR
Jamicon TK 1000uf 10v 0.08 ESR

It would be nice to have better caps but the Jamicon probably aren't the problem.

I have some new jamicons TK here that I recently purchased from maplins store
they read 220uf 50v = 198uf 0.20 esr
..............100uf 50v = 90uf 0.44 esr

And their 100uf 25v are a lot worse, also I find all of there caps are 10 per cent or more under capataince, I asume that he used one of these three on inverter
This link of jamicon clearly show you that they are standard caps and not low impedance
http://www.icd-sales.com/JamiconSeriesGuide.asp

hope this may help, but I am not saying this is the problem only a possibility, I hold my hands up to not knowing
bob