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Dell Dimension E521 Power Board


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#1 AustinTerry

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Posted 19 September 2010 - 05:35 PM

On this Dell computer, it has a front control panel board that has 2 usb parts, mic and headphones jack, and a power switch that is connected to the front power button by a lever.
it has a "ide looking" cable that connects it to the MB. It is a coworkers computer and he had taken it to the GeekSquad a while back because it would not power up, they wiggled the cable and got it to power up. He brought to me, I pulled the board and cable out, googled the part number (which I can't find where I wrote it down now) and was not able to find much info except for some for sale on ebay (the board and cable come together).

After I put it back in, I was able to get Vista to load, but it was all full of Malware and other problems, so I reformatted and re-installed Vista. Installed all updates and the backup files.
Everything was working great! I booted, rebooted, ran everything I could for a few more days and gave it back to him working fine. He said it worked great for one day and then back to the original problem , just a black screen on bootup. I brought it back home, and was able to boot into Vista ok, only allot of problems, like continuing to try and find drivers for the usb mouse, firewall would not load, and various other issues. So I had him bring me his monitor, mouse and keyboard, thinking one of them could be causing the problem.

Well, this morning I hooked his monitor up to it, and sure enough, no picture. The computer sounded like it was on, but no power going the monitor. So I put a known good monitor on it, but same thing. hmmm... So know I'm thinking the power board could be the culprit again or possibly a bad mb. I jiggled the power board and cable a little, and sure enough, I was able to boot back into Vista, with the same issues tho. So know I have all his hardware attached and have re-installed Vista again, (downloading 103 updates at the moment).

Sorry to be so long and drawn out, but wanted to see if anybody has had any experience with these rare Dell front control panel power boards.

Thanks!

Terry

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#2 MrBruce1959

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Posted 20 September 2010 - 11:06 AM

Hello and welcome to Bleepingcomputer.

I am thinking that you may have a faulty contact in the power switch.

I do not know if you have any electronics back-ground at all, such as experience with using a VOM (multi-tester) or soldering iron.

If it was me who had this computer in my possession, I would remove the circuit board from the computer case.

I would use the VOM meter set to either continuity or the Ohms reading mode.

When a VOM meter is set to this mode, the meter is partially connected to one side of the VOM meter's battery, while the other half passes through the meter's probes.

If there is a connection between the probes either through the touching of the probes together, or by the probes being applied to a complete circuit, the battery power flows through the circuit and applies power to the meter, thus causing it to move across the scale.

With this being explained we now have an idea how to use the VOM meter to check circuits for problems.

This meter allows us to check a switch for problems.

Applying the meters RED and Black probes to the two solder lugs, we can find that there is no meter fluctuation or deviation, thus we have an open circuit. This is the default position of the power switch.

If we press the power switch in, the switch closes the circuit, thus we should now have a result on the meter, showing a current flow. The meter should respond and move across the scale.

If the switch is functioning like it is supposed to, this should be the result. However, if the switch is bad, contacts are dirty or noisy, the meter may respond with fluctuation that is intermittent.

You should also check the condition of the plug you said looks like a IDE cable plug as well.

The wires going into this plug could be loose where they are crimped into the lug.

The connector can also be victim of contact corrosion. This can happen over time, causing a faulty intermittent connection to the pins found on the motherboard.

Those connectors can also be expanded and be larger than the pins they are supposed to be making a connection to. This would mean that the connector is sitting over the pin, but since it is wider in size, it does not make actual contact with the pin it is supposed to make contact with.

Sometimes I will take one of the probes from the VOM meter and gently pry the connector into the center a bit, so it is a bit smaller in circumference. This reduces the size and makes it a tighter fit with the pin it mates to on the motherboard. Be careful not to over do this, because if you make the hole too small, the pin won't be able to enter the hole and this will end up bending the pin on the motherboard or cause it to brake off!

Also, you can use the VOM meter to check continuity between the circuits on the circuit board that holds the switch to the connector at the other end of the multi-wire connector that would connect to the motherboard.

This would help determine if the board or the connector has a faulty connection.

Putting one probe in each of the connectors holes and testing for continuity on the circuit board should help you determine if there is a fault in the various circuits.

If you find the switch to be dirty or defective, you may be able to replace just the switch and save the rest of the circuit board with out total replacement.

Switches are usually universal and can be found at any electronics parts store, or can be salvaged from another piece of scraped electronics or computer.

Bruce.

Edited by MrBruce1959, 20 September 2010 - 11:11 AM.

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#3 dc3

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Posted 20 September 2010 - 11:19 AM

The power switch is what is known as a momentary switch, it is like the doorbell button that as long as you press it the doorbell rings. If you don't have a multimeter or continuity meter, you can do the old standby test. Follow the two lead of the switch back to the motherboard to where they connect. Remove the two wires from the pins and use a piece of wire to very briefly short the two pins. If this works then you know that the problem is with the switch, or its connections. The multimeter is the definitive means of trouble shooting this though.

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