EMachines E183HV

[dcapper]

I have been reading on here about the 2 second then black. I tore this unit apart. Replaced the caps. Resoldered a lot of joints. When I put it back together it seems to be working ok but I get a small hum from the display on the top corner by the T-Con, or at least I think it's a T-Con. This normal or should I be looking at something else.

[stj]

Re: EMachines E183HV

you need to look where the hum comes from.

maybe take a foto of the area.

[dcapper]

Re: EMachines E183HV

I'll upload some pics tomorrow.

[dcapper]

Re: EMachines E183HV

Here's the pics I took today. The hissing noise, almost like air coming out of tire, is coming from the panel on the top left (facing the screen). There is only smd caps on the board that connects to the panel but I could replace those if needed. Thanks in advance.

[stj]

Re: EMachines E183HV

o.k.
when it's hissing, can you smell ozone?
like using an ioniser?

because hissing is usually high-voltage arcing.
if it is - you need to inspect the tube ends and wiring on them.

hissing is not the same as hum - it's a much higher frequency.
just saying - because you changed your description.

[dcapper]

Re: EMachines E183HV

Ya sorry, once it was apart it definitely was hissing. No smell though. I'll take the panel apart tomorrow.

[stj]

Re: EMachines E183HV

just an idea,
if it will run with the invertor or tubes unplugged,
try it - if the hissing stops - you have the answer.

[bammbammfran]

Re: EMachines E183HV

there is no t-con on this
recheck your caps to make sure you did not install one backwards and it blew and it's leaking.
if that is okay. unplug the top bulbs and turn it on with vga or dvi connected and the computer on to see if it is gone. Then plug the two top bulbs back in and unplug the bottom ones and try again. It won't stay lit with bulbs unplugged, but when you first turn it on you might hear your hiss for a second if it is a bulb arcing.
if you happen to have an old screen laying around with good bulbs, this would give you a better answer. if you do, plug two bulbs of the old screen into the two that you unplugged from the original screen.

[dcapper]

Re: EMachines E183HV

How can you tell I usually fix tv's not monitors. OK. I'm just going to tear it apart now.

[dcapper]

Re: EMachines E183HV

When I have the panel apart and smell the hissing area, it does have a small odor. Now when I did connect it back up I might have mixed up CN801 and CN802. The cables to the backlight. When I have it connected one way I get emachines for 2 seconds then black then 2 seconds with cable not connected then black. When I have the CN cables reversed I get constant picture but the hissing noise.

I checked all the caps and they are good. It's actually doing the same thing as it was before I changed the caps. I metered the old ones and they were working.

The hissing is coming from the backlight no the screen.

[bammbammfran]

Re: EMachines E183HV

On most monitors you should be able to reverse the backlight plugs

Once in a while some monitor models use one plug for 2 positives and a different plug for the two returns. These types setups would have two thicker wires on one plug and two thinner ones on another plug. Most units have 1 thick and 1 thin wire on each plug

I would need to see a picture of that actual power supply to get a better idea

I still think that one of the bulbs is creating the issue

[dcapper]

Re: EMachines E183HV

I attached a pic of the motherboard. I didn't have the 2 - 330uf 35v caps to change, but I put in 2 - 330uf 25v Rubycon caps I had to test for a few seconds. Same result. Removed the Rubycons and put the originals back in.
Question: Why would I have constant picture plugged in one way but not the other?

[bammbammfran]

Re: EMachines E183HV

not sure why it works one way but not the other.
It may be that the board turns one bulb on just ahead of the other.
I expected to see four bulbs but it look like you only have 2 which used to be in the older 12inch and 15inch screens

Picture looks like 801 should be the top bulb and 802 should be the bottom one
is that the way that it works and buzzes or the does it go 2sec with it plugged in this way.
when you have it plugged in so that it works and buzzes, did you try to unplug just one bulb or the other to see if it stays working.. (some of these 2 bulb systems can sometimes stay on with just one bulb hooked up)

I assume that you do not have any other screens laying around to use to help testing (probably anything from a 15 to a 19 would work)

[budm]

Re: EMachines E183HV

Can you show the bottom side of the board? I still think you do have bad connections at the end of the lamp.
The first picture you have on post 4, it shows that both lamps are on the top of the LCD panel edge only and no lamps on the bottom edge of the panel. Is that right?

[dcapper]

Re: EMachines E183HV

The screen is 18.5". But I did what you suggested and it does the on for 2 seconds off then on again then off. With one cable connected in either plug. The only way I can get it to stay on is with both plugs in and only one way. Bottom cable to top plug and top cable to bottom plug.

After playing some more. I have learned a lot about the backlight system. When I I have it up and running and it's hissing, I put my fluke lead into the positive of the bottom connector (which is connected to the top of the backlight planel), and I get just over 4 volts and the hissing stops but the screen stays on. When I do the same with the top connector the screen turns off. Like you, I'm convinced it's a bad bulb.

I know a meter will put in some resistance. Can I put a resistor inline to decrease the voltage a little to stop the hissing? Although it would increase the current.

[dcapper]

Re: EMachines E183HV

Budm, here is the pic. Also I noticed there is some blue caps before the connectors on the mainboard. I haven't metered them yet. I wonder if one for those is faulty. The connections for the backlight are on the side of the panel and the ribbon cable is to the top of the panel.

EDIT: I metered the 3 blue caps. 2 are reading 0. That could be my fluke, but one is reading open. I metered the same caps from a working board on a different type of monitor and they are all reading 0 on my cap test. Using a Fluke 113 that has capacitance test.

[stj]

Re: EMachines E183HV

if you have a shorted cap, the tube will get hit with the full output fron the transformer inc the dc component - that could stress the fuck out of it!

the caps are to block the dc-component so the tubes are just getting the ac pulses.

try desoldering he caps, then check them for resistance.

[dcapper]

Re: EMachines E183HV

My meter can't read in pf. Just reads 0. So I am assuming these caps work. But after assessing the board closer, I found a cracked smd transistor. Now to find out what it was. The letter are A4W on it. Crossed to a BAV70. Need to find one off an old board I have laying around.

[stj]

Re: EMachines E183HV

BAV70 - double diode with a spec just under that of a 1n4148.
well a pair of them!
meter the caps on resistance-test not capacitance.

[bammbammfran]

Re: EMachines E183HV

The blue caps don't show any discoloring signs of having run hot so they may be ok

The a4w is probably sensing current telling the controller chip that the bulb is on.
if one of the bulbs was arcing, it could have caused that a4w to cook ??
Maybe when you swap the bulb plugs you are putting the good bulb on the side that that burned diode was on and for some reason that allows it to stay on ???