Dell 2209W - no power at all - stripped down but can't see anything obvious

[jetadm123]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

Are you taking these voltage readings with all the boards connected? If not, try it with the inverter board connected.

[Batz]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

I tried again with the secondary board hooked to the primary board (but no other connections attached). The volts are more or less the same. The +5V is perhaps different at 800mV to 1600mV.

Any ideas what could be causing this voltage fluctuation?

[retiredcaps]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

The voltages are really hard to measure because the multimeter is auto ranging and although it has an auto/manual button I can't figure out how to work it.

For most autoranging multimeters, this is how it works.

If you press the auto/manual button, it should switch from auto to manual. Older multimeters should show 0.00V DC. If you press auto/manual again, it should show 0.0V DC. Press once more and it should show 0V DC. Notice how each time, the resolution drops by one? It went from 0.00 to 0.0 to 0.

It starts at the "low" range, and moves up. This mimics the rotary switch on a manual range multimeter where you switch the dial from 2 to 20 to 200V DC.

Anyway here are the readings, they are all rapidly wandering up and down within a period of a second or so:

+5V near C964 between 0 and 1 volt (0 and 1000mV)
+24V near F851 between 16 and 21 volts
+12V near F853 between 600mV and 1.6V

Since your AC is steady and DC is not, there could be a couple of reasons.

1) Something is wrong with your DC functionality on your multimeter.
2) Something is loading down the board causing the power to fluctate.

Let's eliminate #1 as the source of problem first as it is the easiest.

If you have a spare ATX power supply, measure the 3.3, 5.0, and 12.0V DC rails. It all 3 readings are steady, then you know the multimeter is good. If you don't have a spare, you can measure your existing computer's power supply. Alternatively, you can measure some fresh AA, 9V and some used batteries.

As for the schematic, I didn't look at all the other pages, I just jumped to page 38. You will have to be the eyes for us since we will need part numbers from certain locations of the board. These will be the ICs mounted on the heatsinks.

[retiredcaps]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

See pic.

1) List the part numbers of each chip that is mounted onto the heatsinks numbered 1-6.

2) List the part number of the blue circled chip.

3) List the part number of the yellow circled chip.

4) For bonus points, provide a URL datasheet for each component.

5) The component on heatsink #1 looks like your bridge rectifier (a 4 pin black long component - D850). This is where your AC gets rectified into DC.

6) WARNING: When lcd is plugged in and power on, all your heatsinks are likely LIVE so don't touch them.

[Batz]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

Items numbered in red:
1 = D850 (4 legs) on the items itself it says GBU8-06


2 = this has two items:

On the right in the picture is D860 on the items itself it says:
IA32AJ
R860PF2
(2 legs)


On the left in the picture is Q853 on the items itself it says:
11N80C3
HCL032
(3 legs)


3 = Q850 (3 legs) on the items itself it says:
F11NM80
GK01E V3
CHN 036

4 = Q950 (3 legs) on the items itself it says:
2761I
A36 295

5 = this has two items:

On the right in the picture is D853 on the items itself it says:
SRF10-20
0291
(3 legs)

On the left in the picture is D854 on the items itself it says:
SRF10-20
0291
(3 legs)

Both:


6 = this has two items:

On the top in the picture is D961 on the items itself it says:
SRF10-10
0381
(3 legs)

On the bottom in the picture is D960 on the items itself it says:

SRF10-10
0381
(3 legs)

Both: http://www.datasheetarchive.com/SRF10-10-datasheet.html

Blue circled chip reads:
SG6901ASZ
R1A2H873036T


Yellow circled chip reads: (this is really tiny so not 100% sure)
LD7575PS
1039CC


I've tested the multimeter on a few batteries and it seems to be working perfectly. It also seems to work as you describe with the auto/manual button so I can try that the next time I measure.

I'll try and google for the datasheets shortly. Edits: OK I have added those datasheet links where the google result looked like there was one suitable candidate but I haven't done anymore cross checking like reading the manual or anything! Where there is no URL then I didn't get a single result from google that I could be sure of.

[retiredcaps]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

Blue circled chip reads:
SG6901ASZ

Yellow circled chip reads: (this is really tiny so not 100% sure)
LD7575PS

1) Let's get some DC voltage measurements. You can leave your multimeter on autorange. Note some of these will be high voltage so be careful and don't let the probes slip. Plug in the lcd and turn power on.

2) For SG6901ASZ, refer to the datasheet for the pin numbering. Pin 13 is GND (black probe). Record the DC voltage for pin 15 (VDD).

3) For LD7575PS, refer to the datasheet for the pin numbering. Ping 4 is GND (black probe). Record the DC voltages for pin 6 (VCC) and pin 8 (HV - this is high voltage).

4) Measure the DC voltage across capacitor C957 (to the right of SG6901ASZ). Black probe on negative leg and red probe on positive leg of the capacitor.

Note this may be C857. I can't quite make out if it is a 9 or 8.

5) Do the same for capacitor C952 (to the left of LD7575PS).

6) List the uF and voltage for C957 and C952.

7) Measure the DC voltage on D850 (bridge rectifier) on the outer two pins. Black on negative and red on positive. If the D850 has no markings for + and -, you can still measure it, but you might see a negative reading which just means the probes are reversed.

8) Note if DC voltages are steady or fluctuating.

[Batz]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

OK, here goes:

Item 2: 954 mV

Item 3: pins 4&6 = 6.1mV pins 4&8 = 288V

Item 4: yes is C957 = 7.1mV

Item 5: C952 = 6.2mV

Item 6: C957 = 10uF / 50V & C952 = 47uF / 50V

Item 7: D850 outer pins 335V

All readings are steady.

[budm]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

Is the DC voltage still steady on that 450vdc large cap since this power supply has PFC Voltage booster circuits (top left of the picture)?

[Batz]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

Yes it's around 393V

[budm]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

Please tell me the voltages you have on these 3 caps.

[Batz]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

These are: C862, C963 and C 931 and are all reading 0.x mV i.e. zero volts.

By the way I had to disconnect the board to get to the back. I tested some of the voltages from the previous post with the board on it's own and they are just about the same.

[budm]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

That will explain at least why you do not have 5vdc for the logic board to run.
What is the P/N of the SMPS ICs (the small one is for the 5v/12v) as shown in the picture?
We need to get the 5v/12v working first since the main board needs it to function. the 5v/12v should be running the minute the board get the AC power.

[retiredcaps]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

What is the P/N of the SMPS ICs (the small one is for the 5v/12v) as shown in the picture?

Answered in post #25 with voltage readings in post #27.

[budm]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

@retiredcaps, thanks. When the thread gets long, I lost track.
I will download the spec and study them.

[budm]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

OK, more testing needed. Please see the attachments.
The circuits for the 5v/12v is closed to the App notes of the LD7575 as far as I can tell from the traces.

[Batz]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

OK, I think this is what you need, remember you need to keep the directions simple for me ...

Q1. Please ohm out this zener diode zd951
A: in one direction 11kohm in the other direction is starts high but settles on around 53kohm

Q2. Please see if the cathode (black side) is connected to pin 6 (VCC)
A: I measured the resistance between pin 6 of the small IC 7575 and the uppermost leg (in the picture you attached) of the Zener diode and got 6 ohms.

Q3. This leg of D952 should be connected to pin 6 of the IC 7575
A: resistance starts high but drops within 30 seconds to around 63kohms

I hope I have interpreted the queries correctly!

Pictures attached.

[budm]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

"Q3. This leg of D952 should be connected to pin 6 of the IC 7575
A: resistance starts high but drops within 30 seconds to around 63kohms"
This is the key point, this D952 is the one that supplies the voltage to VCC Pin 6 of IC7575. From the resistance reading, it is not correct at all.
I will have to try to trace out the Cathode (banded side of the diode) to see if it is connected to any resistor or fuse of some sort. I will need you to Ohm out to find out what this Cathode side is connected to.

BY the way, you took very clear pictures. What do you use for lighting? Nice job.

[Batz]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

Thanks. I just take the board outside, today it's white cloud so very flat lighting.

[budm]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

OK I trace out the connection of the D952, it looks like the Cathode (banded sided) of D952 is connected to ZD501 Anode side?
By the way, is pin6 (vcc) of the 7575 connected to C957 Postive leg?

[Batz]

Re: Dell 2209W - no power at all - stripped down but can't see anything obvious

Are you asking me to do something specific? :O)
Am I to test continuity or try and visually trace?