Ilex Acme Synchro vs non-Synchro

[williaty]

I've been beating on google trying to get it to answer this question for me and I'm not having any luck

What's the difference between an Ilex Acme Synchro and a Ilex Acme shutter?

Clearly, it has something to do with flash synchronization but both shutters appear to have bi-post so even the non-synchro shutter must be able to sync with flash.

What's the real difference?

[mdarnton]

Someone added sync to the plain Acme? And it's probably just X sync, where the real one has synch for all types of bulbs and electronic (and the sync itself needs to be cocked evey time as well as the shutter).

[Dan Fromm]

Early Acmes were jes' plain Acme with no sync of any sort.

[williaty]

So if the shutter says only Acme on it (no printing of Synchro) and yet has a bi-post connector, it's been modified at some point in its life?

[Mark Sampson]

That would make sense. If it was modified early on, the bi-post may only fire at 'M' for bulbs and not 'X' for electronic flash. Is there a selector switch for X, M, FP? With a bi-post to PC adapter cord, fire your electronic flash to see if you have synch with it. if it doesn't work, a repair shop can remove the 'M' delay.

[cowanw]

The synchro model used a separate gear and spring assembly for the flash timing, apparently to take the weight of usage off of the shutter speed assembly. Plain Ilex (not synchro) could have either flash sync or not. If they have flash sync , the plain Acme shutters used the timing of the shutter speed assembly.