Re: KDS LCD monitor, Sampo Inverter..

Arfa Daily wrote:
"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@xxxxxxxxxxx> wrote in message news:rhMil.12694$Yz.3378@xxxxxxxxxxxxxxx

Franc Zabkar wrote:


On Wed, 04 Feb 2009 22:30:57 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@xxxxxxxxxxx> put finger to
keyboard and composed:



It appears I have a failing inverter with a KDS 17" monitor.
this is a dual unit Sampo QPWBGL9151DG
http://www.lcdpart.com/Products/qpwbgl9151dg.html


I found a pin out on the net and states that pin's
1,2 = 12V, it has that, pin's 3 is a On/Off, it's at
~ 4.1 volts via a resistor from the processor board coming from
a 5 volt source. Pin 4 is a dimmer control, it's at 3.35 volts,
5 is ground/common..

With that, I assume the inverter board should be operating and
generating some voltage to the CCL lamps?

Is my assumption correct? If So, I guess I need to repair the
inverter ?


It could be that the ON signal is active low, in which case shorting
it to ground should turn on the inverter. To find out for certain, you
may find an application circuit in the datasheet for the main IC (top
centre in your photo). It may also be helpful to view the data for the
8-pin ICs below each of the coils.

The usual culprits in inverters appear to be electrolytic capacitors,
so I'd change those first. I'd also reflow the solder joints at the
transformers and coils.

- Franc Zabkar

Ok, i've already tried pulling that On/off signal to ground.
It does nothing, Normally standard markings of on/off is the same
order as +/-, since I'm getting + to that pin from the processor board
via a resistor from a 5 volt supply, I guess that thought is out the
door, but like I said, I did pull it low with out success.

There is 1 electrolytic on that board that seems to be related to both
inverters . I will lift the board from the chassis and inspect closer..

thanks.


I'm pretty sure that I can see two electros on there - one conventional through-hole, and one s.m. Have you looked carefully for a s.m. fuse ? They usually have one soon after the incoming supply, and it is not at all uncommon for them to fail for no good reason. Have you followed print from the on / off control input to see if you can find a transistor that does the actual switching ?

Arfa


Actually, I made a mistake on the vender of the monitor, it's AOC, not a
KDS, I don't know where my head was at on that one.

Any ways, last night I got back into it, yes, the large cap in the view was defective. Spec'ed out to be a 50uf 30v, tested as 1.2 uf.

So, I replaced it with what I had close to it at the time, 47uf, 35V

Still does not fire up how ever, I'm not sure as to what the
"On" signal voltage is suppose to be? Currently I have 4.18 volts when
unit is switched on at the control pin. Since this unit operates from
a 12 volt level, I'm making assumptions that I'll need to insert a video signal and see if this level turns into like 12 volts of so..

At this point, I just assumed the inverter should kick in with no
video signal and at least show something for a short time like a
"No signal" or Menus before it goes to sleep.

Tonight, I am charging up one of my older laptops to be used as a video signal to give this a try...

I may have it fixed, Just may not have one of those monitors that shows anything at all unless I active it out of sleep mode with a
video signal (yellow light)..

P.S.
I didn't want to override the on signal with something higher than
that in fear of unneeded additional damaged.

It sure would be nice if I had a service manual for this to so me the
prints.. To me, this is just a shot in the dark project to see if I can
save this monitor and use it for a spare.. It's not worth it to me to sink lots of money into when you can buy them so cheap these days.


http://webpages.charter.net/jamie_5";

.

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  • Re: KDS LCD monitor, Sampo Inverter..
    ... Franc Zabkar wrote: ... I found a pin out on the net and states that pin's ... Pin 4 is a dimmer control, it's at 3.35 volts, ... I assume the inverter board should be operating and ...
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