Broken Dell 1800FP Power Supply - when and when not to resolder?

[EricRepaires]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Hello Maverick
This Schematic will help you and Plainbill sort your problem out with luck, Its not for your monitor but its your p/suppy to a T.
Also my problems with FP1800 was,
AC input fuse, 0.33 resistor (R923), Mosfet on H/sink that resistor goes to, and power controller ICE2AS01, along with a lot of bad solder joints, particulary the diodes on H/sink that you mention, this may help you,



bob

This Link Ain't Working

[EricRepaires]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Sorry lads messed up somwhere with above link, will try again,



cant understand why other link dont come up,
bob

Hey
I was wondering If you could help me the Power supply Pdf Plz
Thanks

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

I couldn't find the IC being sold anywhere other than Ebay, so took my chances and ordered a couple. It's coming from overseas so won't arrive for a while. In the mean time, I re-installed one of the ICs I had that doesn't show a short across pins 6 & 7 to test voltage across pins 6 & 7 when powered. Voltage measured in the milli-volts. Could some bad components upstream of the IC be causing this problem? I tested the small diode (D907) that's next to the IC off circuit; that tested fine. Also, I get around 160V out of the big capacitor, so that seems to be fine. Any suggestions?

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

They don't sell this IC anymore. Their websites just say product's obsolete. There are still some sellers on Ebay though. But given my past experience with buying this IC via Ebay, I'm a bit reluctant to do so again.

[budm]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Did you try Mouser and Digikey?

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

I bought those 3 ICs from a random seller on Ebay. Do you have a recommendation of a reputable source?

[budm]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Well, even your brand new IC and never been installed is already showing very low resistance between VCC pin and Gnd pin, that is not good so I really do not trust what you have at this point unless you may want to buy the IC from trusted company.

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

I replaced all the capacitors in the power supply except for the large one. I'm still getting zero volts at the output terminals. Can anyone think of anything else I can try before I give up on this power supply?

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

I checked Q902. It wasn't shorted. Nest, I'll try replacing all the capacitors except for the big one. If that doesn't work, not sure what to do next other than to get a replacement power supply.

[jetadm123]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Suggest you check Q902 for shorts (see post #59). If shorted, it can cause the chip to fail.

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Yes, it measured 4.4 ohms off the board. That IC is new and has never been installed. Looks like I received defective merchandise. Hopefully, the other two are still good. Guess the only thing left for me to try is to replace the remaining capacitors. Anyone have another suggestion please post.

[budm]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

"Resistance across pins 6 & 7 on that 3rd IC only measured 4.4 ohms." BAD IC if that measurement is done OFF the board, Notes 6 = VCC, 7 = GND.
ZD902 for the VCC clamping is not installed in your board.

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

I looked over the document from the hyperlink posted by jiroy, but being an electronics neophyte, I wasn't able to get an useful information out of it to help diagnose my problem. Can someone more knowledgeable please help?

[jiroy]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Sounds like many links throughout this thread isn't working anymore so here is the Ic schematic .

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

I soldered on a 47uf capacitor in place of the 33uf one for testing as you suggested. The output terminals still read zero volts. I measured resistance across pins 6 & 7 on the IC that's installed in the power supply again. I got 10.2 k-ohms if I put the red-color probe from the meter on pin 6 and black-color probe on pin 7. If I reverse the two probes, I got 4.2 k-ohms. I'm really confused. Why should reversing the meter probes make any difference when measuring resistance? I also measured the IC that I took out; that one measured 0.6 M-ohms with red terminal on pin 6. I have a 3rd IC that's supposed to be new. Resistance across pins 6 & 7 on that 3rd IC only measured 4.4 ohms. Are these ICs defective? I've attached a photo of one of the ICs with pins 6 & 7 marked (please see ic.pdf). Are those the pins I'm supposed to be measuring? What should the resistance be?

I also measured voltage across terminals 6 & 7 on the installed IC when I had the power supply plugged in to test; voltage was about 0.9 volts. I'm not sure about the zener diode. Can you tell whether I have one from the attached photos?

[budm]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

So you do have DCV to run that standby power supply IC (ICE)
I really do not expect to see 511 Ohm between VCC and GND.
Does your board has Zener diode between VCC and GND?
The 33uf cap with 11 Ohms ESR and shows as 25uF is not good, you can try 47uF in place for testing.

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Yes, the big capacitor had very high voltage (over 150V if I recall). I took out the 50V 47uF capacitor to measure ESR. ESR was really high (measured around 42uF / ESR 7.5 ohms), so I replaced that with a 47uF 160V cap, which was the only 47uF I had on hand. Power supply still output zero volts. I took out the small 33uF/25V capacitor (C924 I think) to test. That also has high ESR with below-spec capacitance (measured 25uF / ESR 11.5 ohms). Unfortunately, I don't have a good 33uF capacitor lying around. I have to order one online. I tested the other radial capacitors in-circuit with my ESR meter. ESRs were ok, but since I didn't remove the capacitors to test, I'm not sure results are all that accurate.

Resistance between VCC (pin 6) and gnd (pin 7) on the IC is around 511 ohms.

Do you think high ESR in C924 could be causing my problem? Should I just replace the other radial capacitors (maybe not the big one)? There are 2 x 10V/2200uF, 2 x 16V/2200 uF, and a 1000uf capacitor in there (what's the voltage on this 1000 uF; I can't read the voltage marking without removing the capacitor) .

[budm]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Are you getting any DCV between the two legs of the main filter cap in the primary side?
We need to have that Voltage first to go further.
BTW, please upload straight shot pictures of the your board.
Also, what is the resistance between VCC pin and GND pin of that ICE IC?

[ptmy3]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

I know this is a really old thread, but I'm hoping someone knowledgeable is still looking at it once in awhile.

A few months ago, my 1800FP had no power when turned on. I repaired it by re-soldering D903 and D906, and replacing the ICE2AS01. Monitor worked great until yesterday when the problem returned - no power when turned on. I measured zero volts between both the 12V and 5V pins and ground on the output connector of the power supply. I thought I may have done a bad job with the soldering the first time, so repleted the exercise. I re-soldered D903 and D906, and installed a new ICE2AS01. But this time, it didn't fix the problem. I'm still getting zero volts on the output terminals. There are no bulges in any of the capacitors. I didn't see any obvious bad soldering joints but decided to re-flowed the solders with a heat gun anyway. But the problem persists. I also check to make sure pins 6 & 7 on the ICE2AS01 wasn't shorted; it wasn't. Anyone have a suggestion on how to proceed next?

[Shane711]

Re: Broken Dell 1800FP Power Supply - when and when not to resolder?

Well, surprise surprise! I didn't believe it would work but I replaced the IC ICE2AS01 and now it works. I bought it for $3.50 and it was the answer. What would I do without "BADCAPS.NET"?