Xerox xa7-19i - ao4620 failed

[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/

[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?

[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.

[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

[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

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

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.

[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

[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

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

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

[jetadm123]

Re: Xerox xa7-19i - ao4620 failed

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

[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