Xerox xa7-19i - ao4620 failed

[emilije]

Re: Xerox xa7-19i - ao4620 failed

OK i'll try to trace. Anything else to do in a meantime while waiting 3193?

PS: i was asking because only that i can trace from pin is always leads to BL and N/F pins, over a transistor or resistors. but ill do another check

[posty]

Re: Xerox xa7-19i - ao4620 failed

Hi, i have a problem with the same monitor, but my problem is that it blows the power when you turn at on. I've looked at the power board and apart from a fuse that had blown. so i replaced that and plugged it in, it did the same. I had a look for any obvious short circuits and there arent any. any idea what it could be?

Thanks
Adam

[retiredcaps]

Re: Xerox xa7-19i - ao4620 failed

I had a look for any obvious short circuits and there arent any. any idea what it could be?

https://www.badcaps.net/forum/showpo...15&postcount=2

[emilije]

Re: Xerox xa7-19i - ao4620 failed

@posty

You may find this schematic useful...if you have Lien Cheng board.
PS: I'm still waiting my parts....

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Dear Plain Bill... your nightmare is almoast over, but only almoast

I've just replaced bit3193, and there was still no voltage to vdd pin. I took 5V directly from conn1 to vdd pin and voila... monitor is working perfectly!

So, obiously problem is somewhere three transistors that we mentioned earlier; by schematic Q101, Q102, Q103 or maybe zener 103 (i didn't measure voltage yet)

New schematic of this board is here; thanks to Skhoda:
https://www.badcaps.net/forum/attach...7&d=1283432613

PS: to be honest, it's not problem to me not to have stby function so can i simply install switch at the bottom of monitor for turn on/off monitor?

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

Dear Plain Bill... your nightmare is almoast over, but only almoast

I've just replaced bit3193, and there was still no voltage to vdd pin. I took 5V directly from conn1 to vdd pin and voila... monitor is working perfectly!

So, obiously problem is somewhere three transistors that we mentioned earlier; by schematic Q101, Q102, Q103 or maybe zener 103 (i didn't measure voltage yet)

New schematic of this board is here; thanks to Skhoda:
https://www.badcaps.net/forum/attach...7&d=1283432613

PS: to be honest, it's not problem to me not to have stby function so can i simply install switch at the bottom of monitor for turn on/off monitor?

Thanks to Skhoda.

Hmm, I had asked you to measure those transistors back in post 36...

SO: While taking 5V directly to the Vdd pin will work, you may want to go with a more elegant solution. With the schematic (Thanks, Skhoda) it's fairly easy to locate the faulty component.

I've numbered the pins of the three transistors, and of the Zener diode. I will want you to make two sets of readings. The first will be with the jumper to Vdd removed, monitor plugged in, and power LED off. Measure the voltage from ground to each of the 11 points. Next, with the power LED on and active (blue or green, whichever this monitor uses) and a video signal being fed to the monitor, measure the same 11 points.

Now for the fun parts. Those transistors have 'package codes' on the top. The one with terminals 4-5-6 seems to be 'PD' and two more letters at right angles. What are the codes on all three? For extra credit, which is Q101, Q102, Q103? Hints: Q101 has one pin tied directly to N/F. Q103 has one pin tied directly to U103, pin 10.

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Oh gee, PlainBill can smile, it takes 50 posts for him to do it

Ok now serious, here are the readings, and you also have the photos:

Q102:
PIN1: blue led off: 0V and when blue led is on: 3.08V
PIN2: blue led off: 0.01V and when blue led is on: 0V
PIN3: blue led off: 0.74V and when blue led is on: 0V

Q101:
PIN4: blue led off: 0.74V and when blue led is on: 0V
PIN5: blue led off: 0.69V and when blue led is on: 0V
PIN6: blue led off: 0.06V and when blue led is on: 0.03V

Q103:
PIN7: blue led off: 0.21V and when blue led is on: 0.24V
PIN8: blue led off: 0.06V and when blue led is on: 0.03V
PIN9: blue led off: 0.72V and when blue led is on: 0V

ZD103:
PIN10: blue led off: 0V and when blue led is on: 0V
PIN11: blue led off: 0.06V and when blue led is on: 0.03V

Codes of transistors are shown in pic.

PS:

The first will be with the jumper to Vdd removed, monitor plugged in, and power LED off.

from practical reasons, this is my "blue led off"

Next, with the power LED on and active (blue or green, whichever this monitor uses) and a video signal being fed to the monitor, measure the same 11 points.

this is my "blue led on"

//serious off:

Hmm, I had asked you to measure those transistors back in post 36..

Hmm, i did, and you said "The transistors (more likely dual diodes) you are getting so excited about are part of the voltage and current sense circuitry"

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

Oh gee, PlainBill can smile, it takes 50 posts for him to do it

Just because I'm smiling doesn't mean I'm happy.

Ok now serious, here are the readings, and you also have the photos:

Q102:
PIN1: blue led off: 0V and when blue led is on: 3.08V
PIN2: blue led off: 0.01V and when blue led is on: 0V
PIN3: blue led off: 0.74V and when blue led is on: 0V

Q101:
PIN4: blue led off: 0.74V and when blue led is on: 0V
PIN5: blue led off: 0.69V and when blue led is on: 0V
PIN6: blue led off: 0.06V and when blue led is on: 0.03V

Wahoo!!! A smoking gun. According to the schematic, pin 5 should be at 14 volts - a direct connection. This could be due to a bad solder joint or a cracked land (trace).

Q103:
PIN7: blue led off: 0.21V and when blue led is on: 0.24V
PIN8: blue led off: 0.06V and when blue led is on: 0.03V
PIN9: blue led off: 0.72V and when blue led is on: 0V

ZD103:
PIN10: blue led off: 0V and when blue led is on: 0V
PIN11: blue led off: 0.06V and when blue led is on: 0.03V

Codes of transistors are shown in pic.

PS:

from practical reasons, this is my "blue led off"



this is my "blue led on"

//serious off:


Hmm, i did, and you said "The transistors (more likely dual diodes) you are getting so excited about are part of the voltage and current sense circuitry"

<Serious mode on.> On a typical day I am TRYING to help anywhere from one to more than half a dozen people.

At one time I managed a test area with upwards of 50 production lots in test or expected to arrive within the next five days. Each lot could require as little as ten minutes of time to several man-days. Part of my job was making sure everything was completed on time. Think of a small railroad marshaling yard where incoming cars must be switched onto the proper tracks so they wind up in the proper order for the outbound trains. This was done without the benefit of a computer. That was then.

Today I have neither the concentration nor the energy to multitask. When I am pursuing a particular train of thought, nothing is more frustrating than finding my 'eyes and hands' are off on something else. I have to make a decision to either continue with the process I was following, jumping to another area, or simply leaving the person to fix the thing by himself. <Serious mode off>

So I was wrong. It was bound to happen sooner or later.

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Dear PlainSeriousBilly,

I put jumper from 14V (actually i measured 14.90V) to "our" pin 5 and there is some strange activity while that jump is connected; i have 7.8V on zener 103, i have 7.6V on VDD pin 10 of bit3193, but i don't have backlight on? I didn't have more time to investigate. Any further ideas?

PS: i don't know is this is coincidence or measurement error, but i've noticed that voltage on vdd pin drops from 7.6 after few seconds to 0.2V after few second back to 7.6....and so on

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

Dear PlainSeriousBilly,

I put jumper from 14V (actually i measured 14.90V) to "our" pin 5 and there is some strange activity while that jump is connected; i have 7.8V on zener 103, i have 7.6V on VDD pin 10 of bit3193, but i don't have backlight on? I didn't have more time to investigate. Any further ideas?

PS: i don't know is this is coincidence or measurement error, but i've noticed that voltage on vdd pin drops from 7.6 after few seconds to 0.2V after few second back to 7.6....and so on

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

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Bill, i don't think that is worth to further investigate this situation. Monitor is working, that was primary objective. I know that permanent 5V is not elegant so can i put a shrack relay to workaround this "problem"? What i meen is, take a relay for powering on/off bit3193, i only don't know from where to take power for relay? (12 and 5V are not trigerred by power on/off switch)

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

Bill, i don't think that is worth to further investigate this situation. Monitor is working, that was primary objective. I know that permanent 5V is not elegant so can i put a shrack relay to workaround this "problem"? What i meen is, take a relay for powering on/off bit3193, i only don't know from where to take power for relay? (12 and 5V are not trigerred by power on/off switch)

I would make another suggestion. Troubleshoot the existing problems.
1. 14 volts does not get to the source of Q101.
2. When 14 Volts is supplied via jumper, Q103 cycles on and off. What happens at the base of Q103, and the gates of Q102 and Q101?

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

dear friend(s) sorry for my delay.
I replaced Q101, 102, 103 and my monitor is now working like a charm.

So thank you all, and especially thanks to you PlainBill for helping me to fix my monitor.

[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.

[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.

[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?

[b700029]

Re: Xerox xa7-19i - ao4620 failed

1 I will get some

2 Yes, it blinks

3 No, not at all

Thanks in advance

[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?

[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

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.