when I heat it up with the solder the unit start normally and work with no issues even if I live it on and working for 24 hours. Or I can pluge the unit on, all lights are Up, leave it for 7- 10 menutes then reconnect and it started normaly.
The unit start up normally when the IC is heated (either by solder gun or a few minutes of operation)? This sounds like a tiny physical connection is broken when cold. But then it is restored when heated.
Just to try anything that might work... Did you flex the board, press down on the IC's, pull up on them, etc.? Examine copper traces with a magnifier/ microscope? Examine for bad solder joints?
Or the problem might be inside the IC. A simple thing such as flexing the pins might cure an intermittent contact. Of course, it is not easy to flex soldered pins, but anything is worth a try.
Also look for a connection which disrupts operation, caused only by cold temperature. This type of problem may be easier to spot visually.
Also check with your voltmeter at various points, both when the unit is cold and when it is warm. Write down volt levels. Look for any differences.
until I head up that chip, then I restart the unit and all voltages are back and unit start normally.
If you are able to get the normal operation at all, then you may have to be content with that, even if you need to heat it up each time you turn it on. You've done very well to remove and replace those devices, and still have a unit that works. It's risky to attempt to repair a commercial unit. One small mistake can ruin it.
Firewire operates within a certain voltage range. Do you read the correct voltage on your board?
Are there times when your Mac recognizes the Apogee? Open 'About this Mac' and look at Firewire parameters. See if your device is listed, and write down parameters. Compare these with parameters you see at other times, when the unit is working or not working, etc.
Does your computer have Firewire 400 or 800 capability?
Is your Apogee designed for Firewire 400 or 800?
Another thing that might be possible, a firmware update. Is this available for your unit?
On the faulty unit, I've found resistance on suspected IC chip legs 58 ohms to ground on working unit about 7 khom.
Yes, that could be important. It implies that the pin has developed internal low resistance to ground (when it is cold, that is).
Perhaps this low resistance path has opened to other places as well.
It may also create a low resistance path to supply +.
Perhaps it affect voltages as you've seen on led's, etc.
Are you determined to try to make it work flawlessly? It's unlikely you can fix a problem inside the IC. Perhaps the best you can do is to mix in a bit of supply+ (through a high-ohm resistor to pin 58). Just enough to lift its voltage a tenth of a volt or two (for a start).
enough to make the IC
First as a safety measure, check resistance across the suspect pin, to the pin that gets supply+. If it is 58 ohms too, then this avenue may be too risky. It means 100 mA is going through the IC, which sounds high.
So be surprised if this cures anything. I'm only suggesting this because you mentioned the difference between the two IC's. If it does work then it is proof that your determination is strong enough to succeed.
OXFW971-TQAG
As far as I understand I have to connect, let say 5 kohm resistor to pin with 58-ohm resistance and ground to elevate a voltage on that pin little bit, just enough to make the IC start.
Does OX stand for Oxford? I purchased an external firewire hd which I later found had an Oxford chip on the board. It lost all data when I accidentally disconnected power. (I got it back using a disk recovery program.) I did some online research and found out the Oxford chip was a major source of problems. A firmware upgrade was recommended.
That is what I would try, if it were me. It will be a big surprise if it works, of course. Remember it's a borderline problem. Don't apply a bigger change than you have to. This is the sort of experiment that can ruin a device. A 400 or 500 ohm resistor may carry too much current into that pin.
Measure volt level frequently, before a change, after a change, before it heats up, after it heats up, etc. You may discover that the unit works more reliably, therefore you want to know exactly what you did to cause it.
Of course 'I am not responsible' if it were to become more problematic.;-)
pins number: 3,22,30,46,50,71,83 and 97 connected together and received +3.276V The resistance of those pins and ground is about 42 ohms when the unit is not plugged in. As soon as I connect the Firewire cable resistance climbed to about 6-7 khom and stays until I disconnect the firewire cable. Then resistance starts to drop slowly to 42 ohms. It takes a while. Looks like some electrolytic capacitor discharges. Also, pin 100 has a resistance around 45 ohms but stay the same even if I force the unit to start with the heat. Pin number 100 dos not connected to those pins I've mentioned before.
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