Safe To Use Old Sync Cord?

A relative tyro when it comes to flash.

I'm looking at a 5 metre pc sync cable - a hang-over from old film days. After searching the forum, I'm looking for confirmation:

~ Can I use this cable safely to trigger a 580EX II from a 20D, 5D Classic, or 1D Classic?

~ I have the understanding that there's no TTL capability: but can I use the 580's power setting to alter output while using this cable?

It's an interim measure until I can get hold of a zebra or similar. But I don't want to experiment until I have some assurance I'm not going to fry a circuit on either body or flash . . .

If the connectors at each end are correct, I see no reason why not. The cable is an "in active" piece of equipment.

I have used a similar one on my 5D Classic and 580Ex without any problem.

You are correct, you will not get e-TTL and it is manual only. So you will have to adjust the 580's power manually.

Thank you. OK, so I'm super-cautious (paranoid?), but It's comforting to have a perception independently confirmed.

Better to be safe than sorry

You should be fine as long as the connectors are correct.

Where the issues with damage comes in is with trigger voltages on the hot shoes of incompatible camera/ flashes i.e. old flashes and modern cameras will end in tears.