Firewire Help

I have fried the FireWire on the logic board on a Mac Pro & IMac 2 different times.
The devices that may have caused a problem the 1st time were thrown away.
The only devices connected the next time were a JVC HD deck & a Firestore digital recorder. AppleCare has fixed the problem but I need to resolve this.
Question: will a Firewire Hub protect the Mac from whatever is causing these problems? Someone suggested a separate FW card that could be trashed if it gets fried but that is not an option for the IMac.
These ar used for video editing...the only way to load video is thru Firewire.
Any ideas???
Thanks

Questions:
1. What, in the present external devices, might "fry" the Firewire connection (bridge?) inside your iMac? Could it be to do with power surge from the external devices?
2. What are the firewire voltage outputs of each device (eg. 5v, or 12v)? What is the firewire voltage tolerance (or limit) of your iMac?
3. Do you have the two present external devices daisy-chained, or are you using two separate firewire connectors?
4. Did the AppleCare people not explain what it was that caused the initial problem?

A firewire hub, unless it has a resistor, or some other limiter, in its circuitry, will probably make no difference to the firewire "fry" factor. But this leads back to what caused the problem in the first place.

Because I had 2 FW failures - a Mac Pro & an IMac - it seemed that one of my devices was causing the problem. Both macs had different video decks connected. The only devices used by both were a LaCie HD that had trouble loading & a combo FW/USB hub....I trashed both of these.
After replacing logic boards in both machines, I connected a Firestore 5v drive - it would not mount on the IMac. The Mac Pro froze when this was connected - when I tried to restart, I lost the power supply.
The Firestore is dead... never a problem for the last 3 years.

I've ordered a Kramer FW hub that should protect the Macs from surges.
Everyone at Mac has been helpful but can't really tell me which device is the problem...there's no way to test any device.

Any other ideas?

I've sent a response to your question via Private Message.