DC coupling capacitor

Dear Forums,
Happy Holidays!
I simulated this very simple circuit as attached and NPN did not turn on as what I thought that the 5V DC power would be blocked by the coupling cap. However, I've seen this section of circuit design had been implemented in one of our products and had been in production for years. Can anyone provide any feedback how it worked?
Thanks,
Kent
Attachments:
DC coupling capacitor.jpg ‏12 KB

Hi Kent,
When DC is first applied current will flow through the capacitor switching on the transistor until the capacitor is fully charged. When the capacitor is charged, current will no longer flow and the transistor will switch off.
This type of cuircuit might be used to perform a once off function on power on for instance. The time the transistor is switched on can be set by chosing the values of the RC network to suit the application.
Regards
Steve

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(Click to see a larger version of the photo)
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================
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Here is the kernal panic log. Thanks. We have done Dr Smoke's Resolving Kernal Panics.
Mon Aug 18 18:46:13 2008
Unresolved kernel trap(cpu 0): 0x300 - Data access DAR=0x00000000449D234E PC=0x0000000000BA1464
Latest crash info for cpu 0:
Exception state (sv=0x2EB9C780)
PC=0x00BA1464; MSR=0x00009030; DAR=0x449D234E; DSISR=0x40000000; LR=0x00BA144C; R1=0x18E4BAD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00670065
backtrace terminated - frame not mapped or invalid: 0xBFFEE490
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Proceeding back via exception chain:
Exception state (sv=0x2EB9C780)
previously dumped as "Latest" state. skipping...
Exception state (sv=0x2F4D8A00)
PC=0x90007878; MSR=0x0200F030; DAR=0x04FAE000; DSISR=0x42000000; LR=0x900073F8; R1=0xBFFEE490; XCP=0x00000030 (0xC00 - System call)
Kernel version:
Darwin Kernel Version 7.9.0:
Wed Mar 30 20:11:17 PST 2005; root:xnu/xnu-517.12.7.obj~1/RELEASE_PPC
panic(cpu 0): 0x300 - Data access
Latest stack backtrace for cpu 0:
Backtrace:
0x00083498 0x0008397C 0x0001EDA4 0x00090C38 0x0009402C
Proceeding back via exception chain:
Exception state (sv=0x2EB9C780)
PC=0x00BA1464; MSR=0x00009030; DAR=0x449D234E; DSISR=0x40000000; LR=0x00BA144C; R1=0x18E4BAD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00670065
backtrace terminated - frame not mapped or invalid: 0xBFFEE490
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.app
Wed Aug 20 07:46:37 2008
Unresolved kernel trap(cpu 0): 0x300 - Data access DAR=0x0000000044BF434E PC=0x0000000000BA1464
Latest crash info for cpu 0:
Exception state (sv=0x2EE8F280)
PC=0x00BA1464; MSR=0x00009030; DAR=0x44BF434E; DSISR=0x40000000; LR=0x00BA144C; R1=0x18E23AD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00000000
backtrace terminated - frame not mapped or invalid: 0xBFFEE5A0
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Proceeding back via exception chain:
Exception state (sv=0x2EE8F280)
previously dumped as "Latest" state. skipping...
Exception state (sv=0x2EE8BC80)
PC=0x90007878; MSR=0x0200F030; DAR=0xE12C4000; DSISR=0x42000000; LR=0x900073F8; R1=0xBFFEE5A0; XCP=0x00000030 (0xC00 - System call)
Kernel version:
Darwin Kernel Version 7.9.0:
Wed Mar 30 20:11:17 PST 2005; root:xnu/xnu-517.12.7.obj~1/RELEASE_PPC
panic(cpu 0): 0x300 - Data access
Latest stack backtrace for cpu 0:
Backtrace:
0x00083498 0x0008397C 0x0001EDA4 0x00090C38 0x0009402C
Proceeding back via exception chain:
Exception state (sv=0x2EE8F280)
PC=0x00BA1464; MSR=0x00009030; DAR=0x44BF434E; DSISR=0x40000000; LR=0x00BA144C; R1=0x18E23AD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00000000
backtrace terminated - frame not mapped or invalid: 0xBFFEE5A0
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Exception st`
Tue Aug 26 07:36:40 2008
Unresolved kernel trap(cpu 0): 0x300 - Data access DAR=0x000000004479434E PC=0x0000000000BA1464
Latest crash info for cpu 0:
Exception state (sv=0x2EB19500)
PC=0x00BA1464; MSR=0x00009030; DAR=0x4479434E; DSISR=0x40000000; LR=0x00BA144C; R1=0x18D53AD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00670044
backtrace terminated - frame not mapped or invalid: 0xBFFEE5A0
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Proceeding back via exception chain:
Exception state (sv=0x2EB19500)
previously dumped as "Latest" state. skipping...
Exception state (sv=0x2EE33280)
PC=0x90007878; MSR=0x0200F030; DAR=0xE12C4000; DSISR=0x42000000; LR=0x900073F8; R1=0xBFFEE5A0; XCP=0x00000030 (0xC00 - System call)
Kernel version:
Darwin Kernel Version 7.9.0:
Wed Mar 30 20:11:17 PST 2005; root:xnu/xnu-517.12.7.obj~1/RELEASE_PPC
panic(cpu 0): 0x300 - Data access
Latest stack backtrace for cpu 0:
Backtrace:
0x00083498 0x0008397C 0x0001EDA4 0x00090C38 0x0009402C
Proceeding back via exception chain:
Exception state (sv=0x2EB19500)
PC=0x00BA1464; MSR=0x00009030; DAR=0x4479434E; DSISR=0x40000000; LR=0x00BA144C; R1=0x18D53AD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00670044
backtrace terminated - frame not mapped or invalid: 0xBFFEE5A0
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.app
Wed Aug 27 07:21:17 2008
Unresolved kernel trap(cpu 0): 0x300 - Data access DAR=0x000000004491034E PC=0x0000000000BA1464
Latest crash info for cpu 0:
Exception state (sv=0x2EBC7A00)
PC=0x00BA1464; MSR=0x00009030; DAR=0x4491034E; DSISR=0x40000000; LR=0x00BA144C; R1=0x18E6BAD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00090009
backtrace terminated - frame not mapped or invalid: 0xBFFEE5A0
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Proceeding back via exception chain:
Exception state (sv=0x2EBC7A00)
previously dumped as "Latest" state. skipping...
Exception state (sv=0x2EE8DC80)
PC=0x90007878; MSR=0x0200F030; DAR=0xE12B9000; DSISR=0x42000000; LR=0x900073F8; R1=0xBFFEE5A0; XCP=0x00000030 (0xC00 - System call)
Kernel version:
Darwin Kernel Version 7.9.0:
Wed Mar 30 20:11:17 PST 2005; root:xnu/xnu-517.12.7.obj~1/RELEASE_PPC
panic(cpu 0): 0x300 - Data access
Latest stack backtrace for cpu 0:
Backtrace:
0x00083498 0x0008397C 0x0001EDA4 0x00090C38 0x0009402C
Proceeding back via exception chain:
Exception state (sv=0x2EBC7A00)
PC=0x00BA1464; MSR=0x00009030; DAR=0x4491034E; DSISR=0x40000000; LR=0x00BA144C; R1=0x18E6BAD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00090009
backtrace terminated - frame not mapped or invalid: 0xBFFEE5A0
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Exception st`
Sun Aug 31 07:29:43 2008
Unresolved kernel trap(cpu 0): 0x300 - Data access DAR=0x0000000044AF434E PC=0x0000000000BA154C
Latest crash info for cpu 0:
Exception state (sv=0x2EE8BA00)
PC=0x00BA154C; MSR=0x00009030; DAR=0x44AF434E; DSISR=0x40000000; LR=0x00BA1FA0; R1=0x18D4BAD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00090009
backtrace terminated - frame not mapped or invalid: 0xBFFEE5A0
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Proceeding back via exception chain:
Exception state (sv=0x2EE8BA00)
previously dumped as "Latest" state. skipping...
Exception state (sv=0x2EE86500)
PC=0x90007878; MSR=0x0200F030; DAR=0xE12E3000; DSISR=0x42000000; LR=0x900073F8; R1=0xBFFEE5A0; XCP=0x00000030 (0xC00 - System call)
Kernel version:
Darwin Kernel Version 7.9.0:
Wed Mar 30 20:11:17 PST 2005; root:xnu/xnu-517.12.7.obj~1/RELEASE_PPC
panic(cpu 0): 0x300 - Data access
Latest stack backtrace for cpu 0:
Backtrace:
0x00083498 0x0008397C 0x0001EDA4 0x00090C38 0x0009402C
Proceeding back via exception chain:
Exception state (sv=0x2EE8BA00)
PC=0x00BA154C; MSR=0x00009030; DAR=0x44AF434E; DSISR=0x40000000; LR=0x00BA1FA0; R1=0x18D4BAD0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA2F28 0x00BA1FA0 0x00B9B3CC 0x00B8B020 0x0027E650 0x00280324 0x0007AC48 0x00021668
0x0001BCE8 0x0001C0F0 0x00094318 0x00090009
backtrace terminated - frame not mapped or invalid: 0xBFFEE5A0
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Exception st`
Tue Sep 2 07:56:56 2008
Unresolved kernel trap(cpu 0): 0x300 - Data access DAR=0x00000000444D634E PC=0x0000000000BA1B58
Latest crash info for cpu 0:
Exception state (sv=0x2EE8C500)
PC=0x00BA1B58; MSR=0x00009030; DAR=0x444D634E; DSISR=0x40000000; LR=0x00B8B5E0; R1=0x18D6BBB0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA1570 0x00B8B5E0 0x0027E650 0x00280324 0x0007AC48 0x00021668 0x0001BCE8 0x0001C0F0
0x00094318 0x00090009
backtrace terminated - frame not mapped or invalid: 0xBFFFDD90
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Proceeding back via exception chain:
Exception state (sv=0x2EE8C500)
previously dumped as "Latest" state. skipping...
Exception state (sv=0x2F795C80)
PC=0x90007878; MSR=0x0200F030; DAR=0x07A44000; DSISR=0x42000000; LR=0x900073F8; R1=0xBFFFDD90; XCP=0x00000030 (0xC00 - System call)
Kernel version:
Darwin Kernel Version 7.9.0:
Wed Mar 30 20:11:17 PST 2005; root:xnu/xnu-517.12.7.obj~1/RELEASE_PPC
panic(cpu 0): 0x300 - Data access
Latest stack backtrace for cpu 0:
Backtrace:
0x00083498 0x0008397C 0x0001EDA4 0x00090C38 0x0009402C
Proceeding back via exception chain:
Exception state (sv=0x2EE8C500)
PC=0x00BA1B58; MSR=0x00009030; DAR=0x444D634E; DSISR=0x40000000; LR=0x00B8B5E0; R1=0x18D6BBB0; XCP=0x0000000C (0x300 - Data access)
Backtrace:
0x00BA1570 0x00B8B5E0 0x0027E650 0x00280324 0x0007AC48 0x00021668 0x0001BCE8 0x0001C0F0
0x00094318 0x00090009
backtrace terminated - frame not mapped or invalid: 0xBFFFDD90
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(3.4.2)@0xb84000
dependency: com.apple.iokit.IOPCIFamily(1.4)@0x398000
dependency: com.apple.iokit.IOGraphicsFamily(1.3.5)@0x436000
dependency: com.apple.NVDAResman(3.4.2)@0x46c000
dependency: com.apple.iokit.IONDRVSupport(1.3.5)@0x456000
Exception state (sv=0x2F795C80)
PC=0x90007878; MSR0

I want to measure PCB 203B force transducer with NI 9234 module in a DC coupled manner - How

The transducer is an IEPE stype and when I turn on IEPE excitation, I can't do a DC coupling. Am I left to using some type of external amp?

From memory, PCB ICP load cells (that's IEPE by another name) have a typical bias voltage of around 10 V, which is usually stripped by a capacitor on the excitation amplifier (or the 9234 in this case). I used to have a series of triaxial load cells that were biased to 10.25 V.
PCB sell a number of relatively inexpensive external amplifiers themselves, but take care to mention to their sales representative that your interest lies in static or quasi-static measurements. I bought a 482C05 four channel amp and decided to use it for low-rate tests, and found that the decay was considerable in one set of tests thanks to the amplifier time constant. One cheap and cheerful solution was to connect a BNC T-piece at the amplifier/load cell connector and branch off the signal. This is where the bias voltage is important - I was fortunate to have a 16 bit DAQ with which I could just about measure signals using the 10 V range - as you would need to remove the DC offset somehow to read with a 5 V DAQ. I was planning on using a nice steady voltage regulator opposing the load cell until I found my DAQ was capable of handling the measurement. On the plus side, DC performance was now no longer affected by the amplifier's frequency response
So, tl;dr - get another excitation source and remove the DC offset voltage if you want to measure in DC coupling.
CLD

MSI Response to bad capacitors

I finally heard from MSI......
Not good news.
I cannot establish where the board was obtained or even the date. I was told it was about a year old but maybe it's an old board that sat for awhile before my friend bought it. Anyhow....MSI said that if it was under warranty then I could send it back to where I bought it....otherwise "I'm on my own"......exact words.
Sooooo...... with that kind of response and customer service, even though MSI boards allow overclocking features and a somewhat reasonable price, I've decided to use other mfg's boards.
Bad business decision by MSI, I think! This is obviously a manufacturing mistake and the capacitors aren't lasting as long as they are supposed to. MSI should really step to the plate and address the problem. From the article I read ABIT is taking care of the problem. I guess I wouldn't be so upset about it but I got a glimpse of MSI revenues and Lelon revenues from last year and they are making a killing.....selling junk.
Anyway...they lost my business....
I don't want to take a chance in the future in buying sub-standard materials from a company that doesn't stand behind their work.

Hi,
The capacitors are failing prematurely because of a faulty electrolyte.
Here is a brief synopsis:
Electrolytic capacitors (elcos) are made from 2 sheets of aluminium foil, separated by an insulator impregnated with electrolyte, rolled up into a cylinder.
Elco manufacturers buy the electrolyte from electrolyte manufacturers.
Elcos in switch mode power supplies operate at high frequencies, with large current flows, and must have low Effective Series Resistance (ESR), and a special electrolyte.
Elcos operating under high stress conditions can generate hydrogen gas unless the electrolyte is designed properly.
Gas build up causes the end of the capacitor to bulge out, and eventually the safety seal at the bottom blows, causing the electrolyte to leak and the capacitor to fail.
The story is that a scientist from a Japanese electrolyte manufacturer was hired by a mainland Chinese enterprise to develop an electrolyte manufacturer. He took a secret electrolyte formula with him.
Some of his team then defected to Taiwan, taking most of the formula with them, but leaving out the magic ingredient which suppresses hydrogen generation.
The Taiwanese company then made large amounts of defective electrolyte, which it sold to Elco makers (presumably at a much cheaper price).
Billions of Elcos were made with defective electrolyte, and sold to various customers including MSI.
MSI (and others) loaded these Elcos onto mobos and shipped them out through the normal distribution channels to end users.
Several months after the defective Elcos were first used, they started to fail. In the meantime, billions had been installed into mobos etc. So there are lots of little time bombs waiting to go off!
So, the failures are due to defective materials (electrolyte), not due to normal wear and tear. If the failure had been, say, the hydraulic fluid used in shock absorbers made by a couple of automotive component manufacturers, and used by several car makers, then in most countries the car makers would have to do a product recall, and change all of the defective shock absorbers - but ultimately recouping the cost from the hydraulic fluid maker (maybe via the shock absorber maker). In my opinion, the mobo makers should be doing a product recall on all the equipment they made using the suspect parts. Now, I don't think that is going to happen, but they should at least be prepared to replace the defective components free of charge, even if the equipment is out of warranty. Remember, the difference is that the components fail because of defective manufacture, not due to normal wear and tear.
As far as I know, very few companies have publicly acknowledged that there is a problem, much less instituted a recall program.
Anyway, I suggest that if you talk nicely to MSI, and remind them that it is a well known component defect, that they might agree to replace the faulty Elcos. (Make sure they replace ALL the suspect capacitors, not just the obviously faulty ones)
Cheers

Does blown capacitors stop imac working or not????

Ive had a real painful couple of weeks with my imac 1.8. Two weeks ago i was deleting some files from my computer and I had my lacie hard disk attached to the computer and i deleted a hidden lacie file. As i put it in the bin my computer just FROSE and i hat to do a restart from the plug.
When I tured it back on the osx would not startup. My computer had lots of files on it so i hat to take it to get recovered, which cost a bit.
I also took it to KRCS which is a apple shop based in the uk. They sent my computer away to be checked and they said that it had blown capacitors and was told this is part of the logic board so would cost over £400 and would not be worth repairing.
The weird bit is, I collected my computer back and the hard disk which had been recovered and refitted the hard disk to the computer and loaded the osx installer disk and it now works??? there does not seem to be any problem with it.
My question is if the capacitors are blown would my computer work?????
sadly one of the people who i went to about my computer problems I think is lying, well it seems like it
but I thought I would ask your advice???
The silly thing is, if i had not got my hard disk back and put it back together the computer would have been thrown away on the advice of KRCS
Many thanks
Tim

Hey Tim,
Sorry to hear of your recent problems.
Yes bad capacitors can make an iMac nonfunctional but it's like that Billy Crystal character:
"There's a big difference between mostly dead and all dead. Mostly dead is slightly alive."
So capacitors can fail in a way that the machine will come back and act normal for a while.
You should look here:
http://jimwarholic.com/2008/07/how-to-repair-apple-imac-g5.php
When you inspect the capacitors, look for just the slightest amount of of bulging. Any that are even slightly domed will be bad. That goes for the ones in the power supply as well.
Report what you find.
If this is an ALS machine it's easy to open up:
http://www.google.com/search?q=site%3Amanuals.info.apple.com%20imac%20g5%20manua l
Probably the 5th one down.
Richard

K7T Pro2 Ver:1 (MS-6330) Capacitor problem

I'm working on a computer for a friend.
It has a K7T Pro2 Ver:1 (MS-6330) motherboard. The Chhsi 2700uF 6.3V capacitor at c172 appears to have failed. The other Chhsi 2700uF 6.3V capacitor at c171 looks ok.
These caps are along the side of the AGP slot. The failed cap is nearest the memory banks.
I did a search of the forum and found a similar problem at:
https://forum-en.msi.com/index.php?topic=49478.0
Does this board have the same voltage regulator problem?
If I replaced the caps, how long might they last if the regulator is questionable?
Should the caps be replaced with a higher value cap, ie 2700uF 10V?
I have the equipment to swap out the caps pretty easily at work, but would it be worth it?
Can the voltage regulator be tested easily?
Thanks for any help.
Paul

Hi,
I'd definitely replace any other caps of the same brand and value, and probably any others of the same brand. Make sure they are low-ESR types.
I replaced about 20 caps on my K7N420 board a few months ago, and all but a couple of them had gone bad by then. I also had to replace four transistors which I think were part of the memory voltage regulator circuits. Boards made in the 2nd and 3rd quarters of 2002 are probably the worst affected, as they were loaded with capacitors which had faulty electrolyte.
As for whether it's worth repairing, or just upgrading? In my case, it cost me about $20 (Australian) for the parts, and a couple of hours of my time, so it was cheaper than paying say $100 or so for a new mobo (and then wanting to upgrade the CPU, and the memory etc.) If I had had to pay someone else to replace the parts, it probably would not have been worth it. The other thing to consider is the impact on the environment. It's more environmentally friendly to do a simple repair on a mobo than to throw it out and replace it. But eventually, the urge to upgrade will become overwhelming. So it's a matter of personal judgement.
Cheers

Counter Coupling

I have a PCI-6602 counter card which I wish to use for a high precision
timing application which involves synchronisation between two counters
generating pulse trains at different frequencies. For this
purpose I need to couple 2 counters - i.e. the output of one
counter should be connected to the source of the second one such that
the second counter generates a pulse train using the 1st counter's
output as its clock/timebase (and hence the second counter's
output frequency is a factor of the 1st counter's). Is there some way
of directly coupling the 2 counters on-board, instead of physically
(externally) connecting the relevant terminals?
Related to this question, can one route a signal onto an RTSI line
using 'route signal.vi', and also read the signal off the same line
(though, to a different destination then where it came from), on the SAME card?
For example, can I route counter 1's output onto an RTSI line and have
it routed to counter 2's source, if counters 1 and 2 are on the same
card? Or does one violate all input/output norms when attempting this?
Thanks for any advice I may get,
Ashesh
Message Edited by Ashesh on 07-04-2006 08:00 AM
Message Edited by Ashesh on 07-04-2006 08:00 AM

Yes, you can definitely route one counter's output up to a RTSI line and then configure another counter to use that same RTSI line as the timebase source. If the counters are on the same card, you don't even need a RTSI cable inside your PC. I used this little trick quite a bit with the 6602 under traditional NI-DAQ. I found it to add helpful flexibility without the need for screwdriver work.
I've switched to DAQmx for new development, and it handles this kind of flexible routing more automatically. No explicity routing to RTSI is needed. Perhaps they use the RTSI routing mechanism under the hood, but I don't really know. If this is a new app, I'd highly recommend DAQmx because traditional NI-DAQ is a bit of a dead-end these days.
-Kevin P.

IMac G5 sudden power shutdown - bulging capacitor on main board

Hi,
does anybody in Europe/Germany have had some experience with Apple dealing with this topic? Does Apple provide an extended warranty for these kinds of hardware malfunctions.
The fact that a 50 Cent capacitor in a so claimed 'high quality' product does fail is really questionable to me. I know that especially the capacitors under frequency switched conditions are under heavy stress, but either the safety margins had been calculated wrong or the item by itself had quality issues.
With best regards.

Hey huhnium,
The fact that a 50 Cent capacitor in a so claimed 'high quality' product does fail is really questionable to me
Well it isn't that the design was bad it's the capacitor plague that affected electronics made from 1999 to as late as 2007. The problem is that you can't tell a bad cap just from external appearance. Re:
http://en.wikipedia.org/wiki/Capacitor_plague
I've also seen this in every brand of PCs I've worked on.
Richard

I use LabWindows/CVI and SCXI modules, how can i check the polarity of a capacitor during an ICT?

I am a newbie using CVi Lab Windows and SCXI modules, how can i perform ICTs to check the proper polarity of a capacitor?

Hello,
That's a big question for a single sentence. Could you give some more details about the hardware you have, and the measurements you want to take?
By the way, when you say ICT, do you mean In-Circuit Test or something else?
Thanks,
John N
Applications Engineer
National Instruments

Loose coupling transport in PI 7.0

Hi,
We are trying to implemet OTO.I am tring to do a loose coupling transport in PI 7.0 from DEV to QUA. I have created one workbench request in se09 and have exported my IR object. I can see my exported IR object in IR>Tools>Find transports. But Open transport organiser is disabled. Can anyone tell me why is it disabled and how to resolved it?
I feel configuration is not proper. Can any one tell me, where the configuration would be wrong.
Please also send me step by step procedures (links) for implementing OTO
Thanks,
Arivarasu S.

Hi,
PI scenario is just used for XI
Regards,
michal

DC coupling capacitor

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