Dell E173FPf

[PlainBill]

Re: Dell E173FPf

OK on the MOSFET. Early in posting I had put that it was a MOSFET but I looked it up and thought it said it was a Schottky.

When I did check the brightness and contrast and turned them both up. The brightness would only go up to around 86 before the lamps shut off.

That is significant in some way. I'm just not sure how.

Where do I measure the output voltages of the power supply?

Measure from the right side of L853 (just to the right of the upper heat sink) to the mounting hole just below it.

Not sure of the mounting of the lamps. Haven't had it far enough apart to see. I just assumed they were vertical because of the left side being dark.

I reversed the CN connections and it did not switch sides.

That would indicate the CCFLs are mounted horizontally and are not getting enough voltage. I just had a brain flash. By the layout of this board, of course the CCFLs are mounted horizontally.

By the way, what are the numbers on the ICC caps you installed. I'm looking for a two or three character series number. It's usually on the same line as the temperature rating.

PlainBill

[goofy173]

Re: Dell E173FPf

Power Supply = 12.19 VDC


On the capacitors, I don't see any series numbers. Here's all that's on them:

ICC
220uF
25 v

The other's the same, except 50 v.

We make pharmaceutical instruments. These may have been from a very large bulk order at some time.

[PlainBill]

Re: Dell E173FPf

Power Supply = 12.19 VDC


On the capacitors, I don't see any series numbers. Here's all that's on them:

ICC
220uF
25 v

The other's the same, except 50 v.

We make pharmaceutical instruments. These may have been from a very large bulk order at some time.

Tentatively, the voltage is good - at least that is a standard voltage.

Is there a temperature rating on the caps? I know ICC makes low esr caps, as well as general purpose caps. The problem COULD be explained by using general purpose caps. Or it could be something else, which would be a bear to troubleshoot without a schematic.

PlainBill

[goofy173]

Re: Dell E173FPf

Ya. a schematic would be good. I think I'll just stick this stuff back on the shelf for a later date.

[goofy173]

Re: Dell E173FPf

I did tear it down to just the lamps. Just connecting the C cables to the lamps, one side of the lamps are lit, the other side is dark, on all 4 horizontal lamps.

[sabre504]

Re: Dell E173FPf

Manual

[PlainBill]

Re: Dell E173FPf

Manual

Wrong manual. That's for the Dell E173FPb (Benq). This is from a different factory.

PlainBill

[sabre504]

Re: Dell E173FPf

Oh sorry but didnt get chance to check properly my fault see if i can find other manual

[goofy173]

Re: Dell E173FPf

Since I hadn't yet said it, thanks to all for your help.

[trobledman]

Re: Dell E173FPf, it works! (so far)

I trash-dug this monitor early this morning and had basically identical symptoms with a near-identical board. The screen was very dim and would go dark within 20-30 seconds, after sliding out the CCFLs they were only flickering at the end with the leads. The most obvious differences between goofy173's board and mine are the silkscreen number being 790271200A00 instead of 790271200800, and my SyncMOS chip being soldered directly to the board instead of being socketed. Everything else looks the same.

Also, it's covered with Su'scon and OST caps...

I thought I'd replace a handful of them on the 12v rail which were all wired in parallel anyway, so I removed a bunch and added a 1000uF Nichicon 35V axial lead cap across some points near the 9960M ICs between the transformers, but it was no good... and probably very silly. Spent $2 at Radio Hack (who stocked a bunch of Lelon and some Elna and some Xicon in the grab bag, but Nichicon for the big 35-50V XXXXuF ones) but I can probably use it elsewhere. I screwed around for a while with various combinations and for a few, I thought I wrecked something but it seems these ICs are just really sensitive to the things on that rail, perhaps even the caps' lead lengths.

Anyway. Playtime ended, and the thing that made it work was a dinky 16V 680uF cap from "xunda" that I harvested from a dead external HDD PSU, soldered to the back of the board to one of the cap's leads at the far end of that 12V rail (in parallel with the 2 original Su'scon 220uF 25V caps which I had to put back to get the lights just to glow feebly again), and then they came up and stayed up and kinda hurt my eyes.

I'll run it like this for a bit and report if it goes down again. I'll probably also buy some that actually match. Hope this helps.

[trobledman]

Re: Dell E173FPf

Update: I can't find an Edit button so I guess I'll just bump... I forgot to mention in my first post that the 12V rail always measured around 12.2V, similar to goofy173's case. That was with a DMM; I wish I had a scope.

Anyway, I left it on for several days hooked to my machine that has DPMS disabled for presentations, and after leaving it off overnight, it reverted to the common "turns on slightly dim for 2 seconds, then off" symptom. I found by turning it on repeatedly that it would eventually warm up, stay on, and regain brightness... nothing new, I suppose. I'm buying new caps.

[PlainBill]

Re: Dell E173FPf

Others use different methods, but in a case where bad caps are suspected, I usually replace the lot of them with Panasonic FM, Fr, or FC. I don't see much benefit in wondering if the replacement cap of unknown quality is actually better or worse than the original cap.

PlainBill

[trobledman]

Re: Dell E173FPf

Others use different methods, but in a case where bad caps are suspected, I usually replace the lot of them with Panasonic FM, Fr, or FC. I don't see much benefit in wondering if the replacement cap of unknown quality is actually better or worse than the original cap.

Right... I also needed to prove to myself that buying caps was worthwhile because something else wouldn't overheat or burn soon after. When I took it apart again just now to make a shopping list, I see that lone 'xunda' cap is bulging. Poor soul... I guess he was just too high-strung...

[PlainBill]

Re: Dell E173FPf

Right... I also needed to prove to myself that buying caps was worthwhile because something else wouldn't overheat or burn soon after. When I took it apart again just now to make a shopping list, I see that lone 'xunda' cap is bulging. Poor soul... I guess he was just too high-strung...

Hey, if someone crammed you into a tiny space, flashed lights at you, and endangered you with high voltages, you'd be high strung too!!!

PlainBill

[trobledman]

Re: Dell E173FPf

Haha yeah, I guess it doesn't help that through its leads it was acting as a sort of heatsink on the only part of the entire board that's discolored by heat-- from those two SMT transformer driver ICs!