Xerox xa7-19i - ao4620 failed

[scokljat]

Re: Xerox xa7-19i - ao4620 failed

Thank you for your help. For now I solved the problem by salvaging SMD parts from other XEROX monitor with blown inverter and pink CCFL tubes. Replaced FAT and diode, few caps and renew some solder joints - monitor works great now.

Thanks and cheers!

Suad

[jetadm123]

Re: Xerox xa7-19i - ao4620 failed

I would think you could also use a 1N4148 diode, which is also similar and very popular.

[budm]

Re: Xerox xa7-19i - ao4620 failed

That is very generic Diode, you can use through hole by just beneding the leads. I will look at the link later.

[scokljat]

Re: Xerox xa7-19i - ao4620 failed

D107 is for Gate discharge when the output pin of the SMPS IC goes LO, you should check the resistance reading to see if the output pin has low resistance reading, for the Diode to be damaged like that, it must have been exposed to the Drain voltage when the MOSFET shorted out. You can use 1N 914 for D107.

Thank you for quick answer :-)

Well, 1N914 is not available in local shops. Would you take a minute and look at the list of available diodes? Some of them are SMD. There is actually 1N914 on the list but it's out of stock.

link:

http://www.chipoteka.hr/proizvodi/130510


Thanks!!!

Cheers,

Suad

[budm]

Re: Xerox xa7-19i - ao4620 failed

D107 is for Gate discharge when the output pin of the SMPS IC goes LO, you should check the resistance reading to see if the output pin has low resistance reading, for the Diode to be damaged like that, it must have been exposed to the Drain voltage when the MOSFET shorted out. You can use 1N 914 for D107.

[scokljat]

Re: Xerox xa7-19i - ao4620 failed

I don't understand that either. I've attached a complete schematic of the board; it appears the other one had errors, or they are different revisions.

PlainBill

Hello,

I'm a newbie and I'll try to reopen this old thread as I believe it's the best XEROX LCD troubleshooter on the web.

I have the same monitor (XA7-19i) with same boards and problem as initial poster. Following directions especially PlainBill's I found some burnt SMD components on inverter circuit.

Symptom is the usual "few seconds to black". After blackout, led lights ok and picture is barely visible with light applied to screen. All CCFL's are off.

I found two visibly burned SMD components at bottom side of PCB. One is U105 FET and other is D107 diode (connected to U102 pin 2).

U105 is AO4606 MOSFET and can be found cheap on ebay.

My question is what is exact value for D107?? What kind of diode is it and what equivalent can I use? Will it work with some standard non SMD 4xxx BAxxx or similar stuff? Any ideas?

Other FET's, diodes measure ok, lot of discoloration around transformers. Replaced one 220u cap, other caps look ok. Maybe I'll replace these two caps near transformers C101 and C105 as they were subjected to lot of heat.

(picture taken with U105 and D107 soldered out)

Thanks in advance!

Cheers!

Suad

[selldoor]

Re: Xerox xa7-19i - ao4620 failed

That is bad news - as you say its probably not an economic repair unless you can pick up another dead monitor with the same panel or need/want practice.
It may be better to offer the inverter/ power supply part here:https://www.badcaps.net/forum/index.php = Down at the bottom there is a classifieds section. People often have difficulty finding inverter transformers if you can make out the numbers and list them with the offer.

[kupervaser]

Re: Xerox xa7-19i - ao4620 failed

I dismantled the screen today and got the bulbs out. Connected them to the inverter and plugged everything on. Indeed the bottom 2 bulbs are pink, the upper 2 are not pink but do not light up completely, on the left i think 5 cm no light at all. All separates bulbs are black on the sides. I checked for replacements, but will cost around 20 euro. I figured it is pointless to go on and repair this screen, for 50 euros I can get a new one. I through it away, but I left the inverter board. If enyone needs it let me know and I will send it to ya for shipping costs.

[selldoor]

Re: Xerox xa7-19i - ao4620 failed

Resistance and Transformers can be tested with nothing else connected.

For most voltage testing everything should be connected.

Bulbs only show as pink when switched on and if they are pink then
yes the only thing to do is to replace them.

[kupervaser]

Re: Xerox xa7-19i - ao4620 failed

Thank you, all right sorry for posting pictures off-site. I have also checked the board very thoroughly and haven't been able to find any faulty components visually.

I ordered the right value capacitors and will change them later when they arrive.
I will check the transformers. Can I test everything with the LCD panel disconnected?

I will check the bulb as well, whether it is pink or not. If it is pink, the only way to fix it is to replace it?

Thanks

[retiredcaps]

Re: Xerox xa7-19i - ao4620 failed

Mine has 2 x 470uF and 4 x 680uf, but I replaced all of them with 6 x 470uF.

You don't want to go down or up in uF. Stick with the original values.

Also, it matters if what type and brand of caps you used for replacements. For the SMPS environment, low ESR (equivalent series resistance) caps are required. While general purpose caps from Radio Shack or Fry's may work, they won't last long.

[selldoor]

Re: Xerox xa7-19i - ao4620 failed

Hmm- yes that is exactly what off-site means.One of the reasons for that is that we put a lot of time in helping to fix things - often referring to the pictures. If they are off site and disappear the text is meaningless and of no help to future enquirers with the same problem. If they are good pictures they can be useful in identifying parts when people have burnt out components etc.
Anyway I have looked and cant really spot anything wrong.

I see budm has suggested testing lamps. I personally find it easier to check the inverter transformers first.
If you have read the 2 seconds to black guide it tells you how to test them. I have to say I have not seen a board like this one. The transformers are the big black rectangles in Pic 9 - I think the secondary winding joints are ( in pic 10) the contacts on each side of the L shaped hole in the board with the trace going to the black wires covered in glue. With power off (for 5 Minutes) check with meter on 2000 ohms the resistance between the two sets of pins, on each transformer - hope that makes sense.The result ( please post numbers) should be within 3% of each other.

I have just re -read your first post - Whilst it is ok to increase voltage values I am fairly sure decreasing uF Values is a bad idea. If /when it gets fixed I would recommend going back and changing these to the correct values as it may impact adversly on other components.
Perhaps budm will comment on this aspect?

[budm]

Re: Xerox xa7-19i - ao4620 failed

It sounds like you have lamp with pinkish glow. You need the test lamp to find out if you have bad lamps or inverter board problem. You can try this:
https://www.badcaps.net/forum/showthread.php?t=19987

Bad lamps:
http://s807.photobucket.com/albums/y...klight%20lamp/

[kupervaser]

Re: Xerox xa7-19i - ao4620 failed

Thank you very much.
I made a few pictures and uploaded on photobucket. Is this ok or is this exactly what offsite means and should not be done, forgive me than.

I have some background in electronics. I have been building mostly guitar pre amplifiers past few years. I also repaired various tube and transistor amplifiers.
I once fixed an LCD screen by replacing the capasitors.
I have a good soldering Iron and my soldering skills are beyond average. I also own an oscilloscope, however I have no clue ho to use it in this application. I use it when troubleshooting audio equipment.

As I stated in my previous post, I already replaced 6 capacitors, 470uf. I have no improvement, screen still goes off in 3 seconds and when on, is red(ish).

Please look at the pictures:

http://s642.photobucket.com/albums/u...ervaser/Xerox/

Thank you.

[selldoor]

Re: Xerox xa7-19i - ao4620 failed

Hi welcome to the forum.
It sounds like one or more of the CCFL bulbs in the panel are going/gone
Turning pink/red is one of the signs.

You probably need to read this guide from retiredcaps: start at post #19
https://www.badcaps.net/forum/showthread.php?t=10419

We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

It will be useful if you can say a bit about yourself - skills tools etc.

[kupervaser]

Re: Xerox xa7-19i - ao4620 failed

Hello, this is an old thread however I hope to get some replies.
I have the same Xerox monitor with 2 issues.

First of all, the monitor goes black after around 3 seconds when I put it on. The same problem as I read all over the internet.
The second problem is, when it is on the colors are not right, it is all red(ish).

I opened it up and did a visual check. Nothing is burned visually. I also replaced the capacitors. Mine has 2 x 470uF and 4 x 680uf, but I replaced all of them with 6 x 470uF.
Nothing has changed. It still goes off after 3 seconds and the colors are bad. Can anyone help me with some next steps to proceed with the troubleshooting?

[b700029]

Re: Xerox xa7-19i - ao4620 failed

1 I will get some

2 Yes, it blinks

3 No, not at all

Thanks in advance

[retiredcaps]

Re: Xerox xa7-19i - ao4620 failed

Hi there. I have the same problem, except mine only works for maybe 2 seconds before dying. It's not the backlight and I've replaced the large capacitors on the board to no avail. It was originally fix-able by turning the brightness to 0 while it warmed up but it's not possible to do that any more.

1) Let's start with clear top down view pictures of your boards so we can suggest test points.

2) Is the power LED still green when the monitor dies?

3) Can you see your desktop wallpaper on the lcd if you shine a flashlight on it?

[jetadm123]

Re: Xerox xa7-19i - ao4620 failed

Hi there. I have the same problem, except mine only works for maybe 2 seconds before dying. It's not the backlight and I've replaced the large capacitors on the board to no avail. It was originally fix-able by turning the brightness to 0 while it warmed up but it's not possible to do that any more.

Unfortunately my electronics knowledge is pretty basic, so I don't really understand what's happening here, but I'd like to have a go at replacing the Q transistors.

My question is what should I replace them with?

Thanks in advance.

If you're using the same board as in the schematic in post #50, then you should be able to look up the part numbers.

[b700029]

Re: Xerox xa7-19i - ao4620 failed

Hi there. I have the same problem, except mine only works for maybe 2 seconds before dying. It's not the backlight and I've replaced the large capacitors on the board to no avail. It was originally fix-able by turning the brightness to 0 while it warmed up but it's not possible to do that any more.

Unfortunately my electronics knowledge is pretty basic, so I don't really understand what's happening here, but I'd like to have a go at replacing the Q transistors.

My question is what should I replace them with?

Thanks in advance.