Xerox xa7-19i - ao4620 failed

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

tested anything that i could. Nothing. Looking for new video board? Any advice?

Initially you had an inverter problem. Now the logic card has a short. I did not feel we were getting close to solving the inverter problem. Isolating a 1.9 ohm short is just about impossible, so replacing the logic card (yes, I know, calling it a video board makes more sense) is the best way to repair that. HOWEVER, unless you are aware of a Xerox xa7-19i monitor to use as a parts donor, finding that isn't going to be easy.

Much as I hate to say it, it's time to give up. At this point the time to repair would be better spent washing dishes, sweeping floors, or selling blood to earn the money to buy a new monitor.

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

tested anything that i could. Nothing. Looking for new video board? Any advice?

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

this is getting weird and weird, worse and worse and more complicated
When disconnected from logic board i have 5v and 12V. when connected to logic board, 5V fails to 1.8v... backlight and brightness signals are 1.3V.

monitor is dead, blue led not blinking.Problem at the logic board?
buaaaa. I didn't do anything wrong, just desoldered pin10 and that cap on power suply/inverter board.

on pic there is logic board, only difference is that on my i have three caps (220uF 16V) near conn1

PS i checked every fuse on logic board, they look ok. 12V is normal.

Make sure you didn't short something out.

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

here are the pic
http://img37.*************/img37/3904/img4559v.jpg

[emilije]

Re: Xerox xa7-19i - ao4620 failed

this is getting weird and weird, worse and worse and more complicated
When disconnected from logic board i have 5v and 12V. when connected to logic board, 5V fails to 1.8v... backlight and brightness signals are 1.3V.

monitor is dead, blue led not blinking.Problem at the logic board?
buaaaa. I didn't do anything wrong, just desoldered pin10 and that cap on power suply/inverter board.

on pic there is logic board, only difference is that on my i have three caps (220uF 16V) near conn1

PS i checked every fuse on logic board, they look ok. 12V is normal.

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Yes, 1.9ohm not kohm, dmm is beeping on 200ohm range!
What do u think about that cap?

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

one step at the time, one step, not three...

Ok, so next step would be to trace shorted zener. Anything else to add?

But the other two people were getting my help (such as it is) first.

think i got it... resistance from pin 10 to gnd is that famous 1.9ohm. When i gently desolder and lift pin 10, from pin 10 to gnd resistance is still 1.9 ohms. From pin 10 lines on PCB to gnd resistance is very high when pin 10 is desoldered and lifted away (140mega ohms). Is this sign that bit3193 is dead?

If you are indeed reading 1.9 ohms, not 1.9K, yes it is.

PS: when pin 10 is desoldered, monitor won't power up (12V present, on 5V there is 1.88V, on backlight and brightness signals there is 1.3V)

That makes absolutely no sense.

The eBay deal strikes me as the best approach. But you can research if by Googling buy BIT3193

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

oops, i forgot to mention. This cap (is it a cap?) in blue circle is 5-20-100ohms (oscilating) and little burned up.

correction; without pin 10 and this cap monitor won't power up.

final suggestions, what to use for replacements?

[emilije]

Re: Xerox xa7-19i - ao4620 failed

think i got it... resistance from pin 10 to gnd is that famous 1.9ohm. When i gently desolder and lift pin 10, from pin 10 to gnd resistance is still 1.9 ohms. From pin 10 lines on PCB to gnd resistance is very high when pin 10 is desoldered and lifted away (140mega ohms). Is this sign that bit3193 is dead?

PS: when pin 10 is desoldered, monitor won't power up (12V present, on 5V there is 1.88V, on backlight and brightness signals there is 1.3V)

if u also think that bit3139 is dead, can u recommend some replacement? i can't buy it in local shops (still i can order it from ebay, but i will need to wait at least 10 days)

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Ahh, crud!!!!I was looking at the wrong datasheet. I guess that's what happens when I'm trying t figure out three different inverters.

one step at the time, one step, not three...

Ok, so next step would be to trace shorted zener. Anything else to add?

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

i don't have my camera anymore to post new pictures, so i have to handle with what i have i have crop and resize one of the good pics.
I'm little bit confused, by datasheet of bit3193 pin 10 (red lines on my pic) is VDD, and pin 2 is error output? I added trace of pin 2, it goes to pin 11 - black lines on pic. Both pin 2 and 11 are zero volts.

other pics are it attach. Those three trans you circled in blue are one that i was so excited yesterday

Ahh, crud!!!!I was looking at the wrong datasheet. I guess that's what happens when I'm trying t figure out three different inverters. I saw the tracing you did from pin 10. That 1.9 ohms to ground is probably significant - it may indicate a shorted Zener diode.

One possible reason for the unusual readings on those three transistors is at least one of them (PD) is a P-channel enhancement mode mosfet.

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

i don't have my camera anymore to post new pictures, so i have to handle with what i have i have crop and resize one of the good pics.
I'm little bit confused, by datasheet of bit3193 pin 10 (red lines on my pic) is VDD, and pin 2 is error output? I added trace of pin 2, it goes to pin 11 - black lines on pic. Both pin 2 and 11 are zero volts.

other pics are it attach. Those three trans you circled in blue are one that i was so excited yesterday

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

Don't know is this helpful to you, but i put my probes on almost every place near inverter controller. This is what i get, on most spots there is zero volts. From conn1 BL signal 2.65V is constant even monitor is in stdby (blue led blinks) N/F signal is 3.08V only when blue led is ON, otherwise iz zero volts.
i took voltage measurement and with ohm meter to show you how the components are connected near bit3139 from pins ON/OFF (pin 6) and VDD pin (pin 10).

That's a big help, but it does leave a few questions unanswered. Still, any progress is good.

First of all, could you take ANOTHER picture, just covering the area within the blue box. Don't bother making any marks on it, I'll be supplying plenty.

Next, I've circled three transistors in blue. Your picture is ALMOST good enough to read the numbers on them. What are the numbers?

Third, Pin 2 of the controller IC is Vdd. Where does that connect (Gee, I guess I better let you mark that in.)

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Don't know is this helpful to you, but i put my probes on almost every place near inverter controller. This is what i get, on most spots there is zero volts. From conn1 BL signal 2.65V is constant even monitor is in stdby (blue led blinks) N/F signal is 3.08V only when blue led is ON, otherwise iz zero volts.
i took voltage measurement and with ohm meter to show you how the components are connected near bit3139 from pins ON/OFF (pin 6) and VDD pin (pin 10).

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Bill, don't be mad at me

I didn't have time to do detailed measurement, but sure will do it tonight just like you said. I'm not home right now so i will do it later.
I forgot to mention why i was getting so excited about that transistors/dual diodes (btw i think on PCB mark is QXXX for them). Lower trans. with his left down pin (if it is a trans, than that pin is B?) is directly connected to backlight ON signal. Right pin next to left is GND. That's the last spot where i can see backlight ON signal, 3.08V.
But OK, maybe i'm wrong, ill repeat my measurement and tracing signals from con1 to inverter controller.
stay cool for now

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

You are killing me. The transistors (more likely dual diodes) you are getting so excited about are part of the voltage and current sense circuitry. First we have to figure out why there is no voltage to the inverter controller.

Let me explain what I would like you to do. There are two signals coming from the logic card to control the inverter. One of these in On/Off; the other is Brightness. The pictures you have given me to work with do not allow me to trace those signal lines - I'm not blaming you for this; even a professional photographer would have serious problems. So you must be my hands and eyes.

Start with this photograph. Set up with everything connected together. make sure nothing can short out. Hook the black lead of the DMM to ground, set the DMM on the 20 VDC range. Hook up power to the monitor.

Trace the Backlight On signal from the connector to the logic card to the components surrounding the inverter controller. The easiest way to do this is to hold the probe on a point, hit the power button twice, watching the voltage change. Note each jumper, resistor, capacitor, and transistor you come to. You SHOULD be able to trace the signal to the point where it reaches pin 6 of the inverter controller. Identify that path by marking up the picture.

Do the reverse for pin 10 - Vdd. It may be switched under control of the. Backlight On signal, it may not be. Again, identify the path by marking up the picture. If you are using Windows, Microsoft Paint will do an acceptable job. Use different colors, please.

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

sorry, i forgot to add attach

[emilije]

Re: Xerox xa7-19i - ao4620 failed

Hm, OK, i tracked down those signals, here is what i saw;

- at lower marked transistor from picture here are voltages:

from B-E is 3.08V
from B-C is 3.08V again
from C-E is 0V

Ok, now this transistor is connected to upper transistor - lower's C is connected to upper's B

- at upper marked transistor here are voltages:

from B-E 0V!!!
from B-C 0V!!!
from E-C 0V!!!

this is a little bit strange? Is maybe one of this transistors faulty?
multimeter diode test is also weird on these trans, not like on others;
lower:
B-E (in one direction is infinity, in other, where red probe is on E there is 1.333)
E-C (in one direction is infinity, in other, where red probe is on E there is 1.855)
other combinations - infinity in both directions
upper:
C-E while red probe is on C there is 1.127
other combinations, in both directions are infinity

I did measurement on three lower transistors of the bit3139 (lower left that you mention), and they have no voltage, from multimeter diode test they look OK.

thnx for help, i know that i'm pain in the ass

PS: when i did multimeter diode test, i didn't desolder transistors but i still think that readings are wierd

[PlainBill]

Re: Xerox xa7-19i - ao4620 failed

C101 - 16.22v
c011 - 16.22v
c020 - 11.82v

for the number of the component on the top part of the heat sink pls look at the pic

Thanks, that makes sense to me. They use a 12V regulator to supply 12V for the logic card instead of using unregulated 12Volts.

My next suggestion would be to trace the Backlight On and Brightness signals from CN01 to the BIT3193. There are three lines that go from the CN01 - power supply area to the inverter. The answer is probably on one of them. I'd pay special attention to the three transistors just below the BIT3193, and I'd check ZD003 near CN01

PlainBill

[emilije]

Re: Xerox xa7-19i - ao4620 failed

C101 - 16.22v
c011 - 16.22v
c020 - 11.82v

for the number of the component on the top part of the heat sink pls look at the pic