HP 1825 Display Black Power Light Green

[printone2]

I have a couple of these HP 1825 (18") monitors that appear to power up (green power light comes on and stays on) but I never see any video with or without a flashlight. There are 13 Capxon caps spread across the power supply and video card. The caps are two different sizes in height 10 mm and 8 mm. The can diameter is 10 mm on all. Looks like I have room for taller cans too.

Here are the markings on the caps:
Capxon 470uf 25v GL 105c c312 vent

I see that Capxon is on the bad list and their site is not available to determine specs of the caps.

None of the caps appear out of shape or leaking. The cards do not appear to have any burn marks on the top side, but I have not turned the PCB over.

The monitor was made in April 2003.

Is there anything I can test at this point or should I assume all the caps are bad before going further?

Can someone make a recommendation on the replacement cap?

The video card is marked Hudson 170b Dual 31381035623

Thanks.

[fuhrer]

Re: HP 1825 Display Black Power Light Green

howdy.have you checked all the necessary voltage going to ze inverter?

[jetadm123]

Re: HP 1825 Display Black Power Light Green

In your first photo, try checking the output of the voltage regulator. I believe it's the device right above the bar code label (looks like VIN and GRD? are marked next to it). What's the part number on the device?

[fuhrer]

Re: HP 1825 Display Black Power Light Green

you can also try testing ze continuity of ze fuse..it's on the left side of the connector cn1 in the inverter board

[printone2]

Re: HP 1825 Display Black Power Light Green

I see that I have three wires farthest from the fuse have -12v, the next has -8.5v, the fifth has -7.5v and then the sixth and seventh show no voltage and the last wire is ground.

The fuse tested good for continuity.



On the voltage regulator I have 5v on the lead marked "vin" and 2.5v on the center lead. The part # is CHN K310 LT25 Brand seems to be SI. That is the best I can make of the markings on the voltage regulator.

[retiredcaps]

Re: HP 1825 Display Black Power Light Green

I see that I have three wires farthest from the fuse have -12v, the next has -8.5v, the fifth has -7.5v and then the sixth and seventh show no voltage and the last wire is ground.

The fuse tested good for continuity.

What are you using for ground on your voltage readings? The readings should all be + DC V.

Continuity can be misleading. On some multimeters, something is continuous if the reading is less than 1800 ohms. I suggest remeasuring the fuse and using just 200 ohms (if manual range). A good fuse should measure less than 1.0 ohms.

[printone2]

Re: HP 1825 Display Black Power Light Green

I have the com lead on the first colored wire, which I thought was ground. The other wires are all the same color.

I read .8 at 200 ohms. My test leads give different readings if I use a different part of the lead, but the cleanest reading is in the .8 range with the fuse off the board.

[retiredcaps]

Re: HP 1825 Display Black Power Light Green

I have the com lead on the first colored wire, which I thought was ground.

I read .8 at 200 ohms.

For ground, use a ground screw nearest the connector. Retest and post voltages for pins 1-8.

Your fuse is good if it measures 0.8 ohms.

[printone2]

Re: HP 1825 Display Black Power Light Green

For ground, use a ground screw nearest the connector. Retest and post voltages for pins 1-8.

Your fuse is good if it measures 0.8 ohms.

Pin 1 11.9 (red jacket)
Pin 2 11.9 (all others gray jacket)
Pin 3 11.9
Pin 4 4.6
Pin 5 3.2
Pin 6 0.0
Pin 7 0.0
Pin 8 0.0

[retiredcaps]

Re: HP 1825 Display Black Power Light Green

Pin 1 11.9 (red jacket)
Pin 2 11.9 (all others gray jacket)
Pin 3 11.9
Pin 4 4.6
Pin 5 3.2
Pin 6 0.0
Pin 7 0.0
Pin 8 0.0

These readings make more sense. pin 4 seems a bit low if it is supposed to be 5V DC, but let's assume it is good for now.

Above the 2 black transformers on the inverter board are four 8 pin ICs. What are the part numbers for each?

[printone2]

Re: HP 1825 Display Black Power Light Green

These readings make more sense. pin 4 seems a bit low if it is supposed to be 5V DC, but let's assume it is good for now.

Above the 2 black transformers on the inverter board are four 8 pin ICs. What are the part numbers for each?

The two IC closest to the edge.
4416
(some mark maybe a zero with a slash or a trademark then) AG(delta)
W32B
These markings are very hard for me to see, but yes they are:

f P310J
fds
4435

[jetadm123]

Re: HP 1825 Display Black Power Light Green

I see that I have three wires farthest from the fuse have -12v, the next has -8.5v, the fifth has -7.5v and then the sixth and seventh show no voltage and the last wire is ground.

The fuse tested good for continuity.



On the voltage regulator I have 5v on the lead marked "vin" and 2.5v on the center lead. The part # is CHN K310 LT25 Brand seems to be SI. That is the best I can make of the markings on the voltage regulator.

The 2.5V output looks good. Not sure why you're not at least getting an image using your flashlight.

[printone2]

Re: HP 1825 Display Black Power Light Green

Pin 1 11.9 (red jacket)
Pin 2 11.9 (all others gray jacket)
Pin 3 11.9
Pin 4 4.6
Pin 5 3.2
Pin 6 0.0
Pin 7 0.0
Pin 8 0.0

Now it makes sense the colored wire is just wire number 1 like on centronics or scsi cables and connectors. I just have not thought in those terms for a long while.

[retiredcaps]

Re: HP 1825 Display Black Power Light Green

4416
4435

Datasheet for 4416



Datasheet for 4435



If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any ohm reading is less than 30 ohm you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

Simply test

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms

Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.

[printone2]

Re: HP 1825 Display Black Power Light Green

Datasheet for 4416



Datasheet for 4435



If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms .6 .6
b) black on pin 1- red on pin 3 - record ohms .6 .6
c) black on pin 2- red on pin 3 - record ohms .6 .6

If any ohm reading is less than 30 ohm you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

Simply test

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms

Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.

The first step seems clear enough, using the small dipple as the pin 1 indicator I measured .6 on all of the pins listed on the 4416 MOSFET. I have not desoldered them, but tested in circuit with power off and power disconnected. When I take into account the datasheet it becomes less clear. When I tested the 4416 according to the datasheet s1 is pin1 and g1 would be pin 4 from my reading, is this correct? That reading was 1. Is this making sense?

[printone2]

Re: HP 1825 Display Black Power Light Green

I have one of the panels that lights up!! The LCD is smashed, but the CCFL light up. I have vertical lines and only a few square inches of normal looking video. This would indicate that I should be able to swap some parts between the monitors. Any suggestion on which board would be the first one to swap, or other suggested course of action?

[retiredcaps]

Re: HP 1825 Display Black Power Light Green

When I take into account the datasheet it becomes less clear. When I tested the 4416 according to the datasheet s1 is pin1 and g1 would be pin 4 from my reading, is this correct? That reading was 1. Is this making sense?

Sorry, my mistake. I cut and paste my "template" for testing mosfets. The first test is for FETs are thare 3 pins only.

Since your mosfet is more than 3 pins, just test S1-G1, S1-D1, G1-D1 combos. The datasheet will tell you what is S1 and D1. So if the datasheet says S1 is pin 1 and D1 is pin 4, that is correct.

If "1" is on the left hand side of the multimeter, that means it is out of range or infinite for that ohm scale. Proceed to finish the rest of the measurements.

[retiredcaps]

Re: HP 1825 Display Black Power Light Green

Any suggestion on which board would be the first one to swap, or other suggested course of action?

Swap Inverter first.

[printone2]

Re: HP 1825 Display Black Power Light Green

Swap Inverter first.

Confirmed in known working lcd with cracked panel that the voltage going to the inverter was the same as measured in the dark lcd.

Swapped known good inverter into dark lcd. Power light stays on as usual and I get the same results as with the previous inverter, no CCFL.

Do you suspect I have bad tubes or a bad video card?

[jetadm123]

Re: HP 1825 Display Black Power Light Green

Go ahead and swap in the logic/video card