fixing a Levono/IBM 6659 PCD monitor (any idea what part 'F701' might be?)

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Hi all,

I'm trying to fix a 6659 monitor which is showing some odd symptoms.
When I got the monitor it would power up roughly 50% of the time. The
other 50%, pushing the power button did nothing. I suspected that it
might just be an issue with the power plug socket on the monitor, so I
opened up the case. Unfortunately, while probing around with it
plugged in, I must have shorted something since I soon got a whiff of
fried component and the monitor now powers up 0% of the time.

Visual (and olfactory) inspection have led me to suspect a surface
mount component labelled 'F701' might be the culprit. This part is
sort of translucent, possibly with a piece of wire running through it
(maybe its a fuse?). It has '4FT' printed on it. Any ideas what it
might be? Better yet, anyone have schematics for the 6659?

thanks!
Graham

 

[[email protected]]

Hi all,

I'm trying to fix a 6659 monitor which is showing some odd symptoms.
When I got the monitor it would power up roughly 50% of the time. The
other 50%, pushing the power button did nothing. I suspected that it
might just be an issue with the power plug socket on the monitor, so I
opened up the case. Unfortunately, while probing around with it
plugged in, I must have shorted something since I soon got a whiff of
fried component and the monitor now powers up 0% of the time.

Visual (and olfactory) inspection have led me to suspect a surface
mount component labelled 'F701' might be the culprit. This part is
sort of translucent, possibly with a piece of wire running through it
(maybe its a fuse?). It has '4FT' printed on it. Any ideas what it
might be? Better yet, anyone have schematics for the 6659?

thanks!
Graham

Fuse, 4AT is 4Amp Time delay. But fuses dont olfact when they go, so it
sounds like something else is wrong. Freecycle might be quicker.


NT

 

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Thanks, the fuse was indeed blown. However, after replacing it, I'm
back to where I started with this odd behavior of powering up only half
the time. This occurs even when the monitor has been sitting
undisturbed, so I don't think its a loose connection. In fact, it
almost seems as though the problem only occurs after the monitor has
been plugged in for a while (maybe 30 mins), but this might be
coincidental.

I'm pretty sure the problem is somewhere on the '48.L2501.A04' board;
not very specific I know. Is anyone familiar with this or similar
monitors? Any ideas as to what parts I should look at replacing? Any
idea where a schematic could be found?

thanks again,
Graham

 

[[email protected]]

Thanks, the fuse was indeed blown. However, after replacing it, I'm
back to where I started with this odd behavior of powering up only half
the time. This occurs even when the monitor has been sitting
undisturbed, so I don't think its a loose connection. In fact, it
almost seems as though the problem only occurs after the monitor has
been plugged in for a while (maybe 30 mins), but this might be
coincidental.

I'm pretty sure the problem is somewhere on the '48.L2501.A04' board;
not very specific I know. Is anyone familiar with this or similar
monitors? Any ideas as to what parts I should look at replacing? Any
idea where a schematic could be found?

thanks again,
Graham

Are you far from civilisation? If not, why spend time on it?


NT

 

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Are you far from civilisation? If not, why spend time on it?


NT

3 reasons:

1) First, the 6659 is a pretty fancy display (21" and will do
2048x1536) and I got it for free because of its flaky condition.

2) I'm a graduate student and don't have money to buy a new display or
pay for this one to be repaired.

3) I thought it would be fun!

 

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3 reasons:

1) First, the 6659 is a pretty fancy display (21" and will do
2048x1536) and I got it for free because of its flaky condition.

2) I'm a graduate student and don't have money to buy a new display or
pay for this one to be repaired.

3) I thought it would be fun!

Right I see. Well, repairing smpsus driving EHT stages is not
especially straightforward, so if youre a graduate student I dont think
your odds are very high on this.

However if you must, the smpsu is refusing to start: why? Either its at
fault or its going into protection mode because of a fault downline,
which usually means a horizontal output area fault.


NT

 

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Right I see. Well, repairing smpsus driving EHT stages is not
especially straightforward, so if youre a graduate student I dont think
your odds are very high on this.

Just out of curiosity, are there typically EHT stages in LCD monitors?
Maybe for the backlight?

However if you must, the smpsu is refusing to start: why? Either its at
fault or its going into protection mode because of a fault downline,
which usually means a horizontal output area fault.

A bit more info on the symptoms which might serve as a clue: For about
10 minutes after the DC powersupply is plugged in to the monitor, the
unit will power up fine. However, after it has sat for 15 or 20
minutes plugged-in, it will then refuse to power up until its unplugged
and then re-plugged in. The powerswitch is just a SPST button (checks
out fine) that pulls a logic signal low. That's about all I could get
from probing the (multi-layer) board. Strange symptoms, but I'm hoping
useful info for someone more experienced than me.

thanks,
Graham

 

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Just out of curiosity, are there typically EHT stages in LCD monitors?

no, i was thinking it was crt for some reason.

Maybe for the backlight?

CCFLs do run on HT

A bit more info on the symptoms which might serve as a clue: For about
10 minutes after the DC powersupply is plugged in to the monitor, the
unit will power up fine. However, after it has sat for 15 or 20
minutes plugged-in, it will then refuse to power up until its unplugged
and then re-plugged in. The powerswitch is just a SPST button (checks
out fine) that pulls a logic signal low. That's about all I could get
from probing the (multi-layer) board. Strange symptoms, but I'm hoping
useful info for someone more experienced than me.

thanks,
Graham

if its lcd its more likely to just be the psu.


NT

 

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If i remember correctly 48.L2501.A04 is made by Benq, Benq 's quality
is not very good compare to other makers.
IF the UL number of your IBM monitor is E144906, then i am 100% sure it
is a Benq one.
Since the fuse blow again, i think the problem is at the primary side
of the board(before AC convert to DC)
I guess you can check whether there is a cold solder join at the
primary side of the board, And also look at the capacitor and
transistor and see if they got damage or not.

 

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Sorry, if did not see your second reply when i first reply.
You said on the second reply, that it needs a restart after 15 min.
I see a whole bunch benq 's lcd has the same problem, sometimes it is
the transistor, or capacitor, transformer, or even cold solder joint.

If you have an ESR meter, you can check the capacitor(disacharge the
big cap before mesauring it)
Colder solder joint is easy to find, just need to look carefully.
Transformer(inverter) is liitle bit difficult, Since it is difficult to
find the replacement

First i will look at the board, and see any discoloration(if something
run hot for a long time, it will change the color of the board.) If
somthing run very hot, it usually break first.
Then Measure the cap with esr meter,check colder joint, then measure
the voltage of different rail, and find out which section cause the
problem.

Usually the manfacturers don't give out any service manual, but if you
want to learn how lcd
power supply works, you can goolge "hp vf17 manual". This is a service
manual for HPvf17, it has the block diagram and flow chart. It teachs
you a lot so read it carefully and try to understand it as much as
possible.


i guess your lcd may has bad caps or colder solder joint, since you
can't power it up 50%of the time and it needs a restart will made the
lcd alive again.