Dell Ultrasharp 1800 no power

[Welchs101]

Hi, I have a dell ultrasharp 1800 that i am trying to fix.

Note: I have read numerous posts on this type of monitor failing due to the ICE2AS01 chip failing. Apparently from VCC to GND there is a short of about 13ohms. For THIS monitor the GND to VCC reading is in the MEG-ohms so my first reaction is the ICE2AS01 chip is ok.

Symptoms of this monitor:
1-WHen i plug in the power......nothing happens. The LED light does not come on.

2-I did measure the voltages at the connectors 1 and 2 (CN1 and CN2 respectively) see enclosed pics.

For CN1: (DC voltages)
Pin1: 5.09V
Pin2: 0V
Pin3: 0.24V
Pin4: 0.26V
Pin5: 5.08V
Pin6: 5.08V


For CN2: (DC voltages)
Pin1: 12.09V
Pin2: 12.09V
Pin3: 0V
Pin4: 0V
Pin5: 5.09V
Pin6: 5.09V
Pin7: 0V
Pin8: 0V


3-I also measured the DC voltage across the big cap: I measured 167.9V

I have no idea as to what to try next. If its the logic board that is "bad" then i dont think its worth replacing.....but i dont even know how to determine this.

Can someone help? Any ideas on what to try would be appreciated.

[retiredcaps]

Re: Dell Ultrasharp 1800 no power

Symptoms of this monitor:
1-WHen i plug in the power......nothing happens. The LED light does not come on.

I have no idea as to what to try next. If its the logic board that is "bad" then i dont think its worth replacing.....but i dont even know how to determine this.

On the logic board, I think I see 3 voltage regulators (just left of the big chip in the middle).

They may be marked AL1117-33 indicating a voltage regulator with 3.3V DC output.

List the part numbers and see if the voltages match the chip designation. See post #5 at

https://www.badcaps.net/forum/showth...ghlight=daytek

for examples.

[Welchs101]

Re: Dell Ultrasharp 1800 no power

The 3 voltage regulators are
1) 1117S25
2) BA033
3) KA78M05R

(see enclosed pic)

I plugged in the power cord and measured the voltages at the respective pins.

1) 1117S25
Pin1: 0V
Pin2: 0V
Pin3: 0.162V

2) BA033
Pin1: 0.162V
Pin2: 0.001V
Pin3: 0V

3) KA78M05R
Pin1: 12.09V
Pin2: 0V
Pin3: 5.09V



So it appears that (1) and (2) either are "bad" or just dont have the correct voltage input. My guess is they dont have the correct voltage input.......what does this mean?

[PlainBill]

Re: Dell Ultrasharp 1800 no power

The 3 voltage regulators are
1) 1117S25
2) BA033
3) KA78M05R

(see enclosed pic)

I plugged in the power cord and measured the voltages at the respective pins.

1) 1117S25
Pin1: 0V
Pin2: 0V
Pin3: 0.162V

2) BA033
Pin1: 0.162V
Pin2: 0.001V
Pin3: 0V

3) KA78M05R
Pin1: 12.09V
Pin2: 0V
Pin3: 5.09V



So it appears that (1) and (2) either are "bad" or just dont have the correct voltage input. My guess is they dont have the correct voltage input.......what does this mean?

Open fuse, open inductor, bad solder joint, or shorted load.

PlainBill

[retiredcaps]

Re: Dell Ultrasharp 1800 no power

1) 1117S25
Pin3: 0.162V

2) BA033
Pin1: 0.162V

Wiht power off and LCD unplugged, I suggest tracing/ohming out the above VIN pins "backwards" to the components that feed the voltage. Make a quick diagram. Then, with power on, see where the Voltage disappears?

[Welchs101]

Re: Dell Ultrasharp 1800 no power

Things moving a little slow. I am trying the suggested things......just moving slow.

I did have a question. I found a post online somewhere that indicated that the chip U501 had problems. The Part U501 is a motorola chip with part number MC68HC908BD48IB.

I have enclosed what i think is the data sheet for this part. But i have no clue as to how to determine if this chip is working ok or not.

[bonney]

Re: Dell Ultrasharp 1800 no power

have a look at page 30 and 31 then check if you have power in or out

[Welchs101]

Re: Dell Ultrasharp 1800 no power

I have power on pin5 but i am not sure what pin to look at to determine if i have "stuff coming out".........

[bonney]

Re: Dell Ultrasharp 1800 no power

pin 5 is Power supply input to the MCU.
pin 2 is 3.3V regulated output from the MCU.
pin 9 is reset

[Welchs101]

Re: Dell Ultrasharp 1800 no power

Pin2: 3.39V dc
Pin5: 5.08V dc
Pin9: 5.08V dc

Does this mean the chip is ok?

[bonney]

Re: Dell Ultrasharp 1800 no power

were does pin 2 and pin 9 go to?

[Welchs101]

Re: Dell Ultrasharp 1800 no power

ok.....i am not making much progress.

I was wondering if someone help guide me on what i should do next to try and narrow down the problem.

[Welchs101]

Re: Dell Ultrasharp 1800 no power

Any ideas on what to check to figure out whats going on? Please help? I will do my best to get back to you in a reasonable time.

[bonney]

Re: Dell Ultrasharp 1800 no power

have you traced to see were pin 2 and pin 9 go to ?

[PlainBill]

Re: Dell Ultrasharp 1800 no power

Any ideas on what to check to figure out whats going on? Please help? I will do my best to get back to you in a reasonable time.

The best thing to do is put it on the shelf and hope a working logic board comes along. Pin 9 is active low - that means the processor should be operating. But something isn't working, and your capability of identifying the defective part is limited. Just as a guess, I would say the most likely candidate is U501. However, that contains a custom ROM, and the proper part is no longer available.

Looking at the board, it uses 6 chips to perform the functions usually accomplished by 1 chip. That screams 'old design'.

PlainBill

[Welchs101]

Re: Dell Ultrasharp 1800 no power

Sorry for not responding until now.........in-laws were in town.

Bill, thanks for the advice.