Synchro Compur wear

SalveSlog · Sep 12, 2015

I've got a Synchro Compur that probably need CLA, but I'm not up to that (yet).
Speeds are quite stable and almost up to nominal up to 1/50, but especially 1/250 and 1/500 is unstable.

Is it possible to say anything about what wear typically does to a Synchro Compur?

BrianShaw · Sep 12, 2015

Most often the problem is gummy lube more than worn out parts. Most common "wear" item is synch contacts.

shutterfinger · Sep 12, 2015

All parts wear. The blade controller no longer moves freely causing the main tension spring to weaken and the pivots on the blades to develop play. The delay timer no longer turns freely so it slows down adding wear on the delay timing spring. The closer to stoppage a shutter is run the more likely it will not return to near correct speeds.

Pioneer · Sep 12, 2015

That is rather interesting. I usually see more inconsistency in the lower speeds, not the faster ones, when one of my leaf shutters is due for cleaning.

AgX · Sep 12, 2015

shutterfinger said:
The delay timer no longer turns freely so it slows down adding wear on the delay timing spring. The closer to stoppage a shutter is run the more likely it will not return to near correct speeds.

How can a retarded delay timer put addiditional wear on the respective spring? It is stressed by the max. extension and the cycles. Not by the relaxation time, at least not by retarded relaxation time.

What do you mean by "closer to stoppage"?

BrianShaw · Sep 12, 2015

It a bit odd to read both "perpetual motion" and "kaput" in the same paragraph. Ha ha.

shutterfinger · Sep 12, 2015

COMPUR Shutters of all branding use a spiral torsion spring ( like a watch or clock mainspring ) for delay gear timing. The increased difficulty of turning the delay pallet and associated gears, usually 3, wears the timing delay spring.

snikulin · Sep 13, 2015

SalveSlog said:
1/250 and 1/500 is unstable.

Can you define "unstable"?

On all my Yashica TLRs (seven so far) the highest speed measurement gives the "pervious" speed.
E.g. 1/500 measures at about 1/250 but 1/250 is about right.
1/300 on older cameras usually gives 1/200 or even 1/100.
Test to test variance is always large, up to 30%.

I measure shutter speed with light emitting diode at 100KHz, phototransistor connected to PC (a regular integrated Intel audio DAC) and Audacity audio editor.
I think the setup is sound but I never had a known good shutter to calibrate the bench.

I attribute the slowdown and instability effects to weakened master spring.
I think all springs deform and weaken in sixty or seventy years, especially if stored cocked.
I just live with it and shoot BW only.

SalveSlog · Sep 13, 2015

Here is a series at 1/250:
1/177
1/217
1/213
1/158
1/160
And now 1/500:
1/298
1/258
1/366
1/263
1/268
Using aperture f:3,5
I'm hooked on slides, so I would have liked it more stable than this.
(Like you, I'm a bit unsure about my setup for measuring. I used this scheme.)

paul ron · Sep 13, 2015

The lack of regular service wears more on a shutter than actual use.

As the old lube gets gummy n hard or nonexistant, parts get more stress.

Old pros did regular maintenance whether it needed it or not. Like taxi cabs getting oil changes every month. They make a living off their equipment unlike amatuers that will use it to death till it shows symptoms then say what a piece of crap it is.

snikulin · Sep 13, 2015

SalveSlog said:
Here is a series at 1/250

Yep, that's a very familiar picture.
I have about the same data from my Mark Hama serviced Yashica 12.
Weak 1/250 could be blamed on the dirty escapement.
A shutter without escapement works on its fastest speed and the escapement produces all necessary delays.
Proper CLA should bring that 1/250 closer to true 1/250 but won't fix 1/500 and will leave it at the same ~1/250-ish level.
So in my opinion that lower speeds instability is somewhat fixable by escapement CLA, 1/500 problem is not fixable: I am not aware of any repairmen who changes master springs in old shutters.

BrianShaw · Sep 13, 2015

That instability could be measurement instability as much, or maybe even more, than shutter instability. The shutter for sure seems inaccurate. But also remember, OP, that factory spec is 1/3 stop or so... And that's historically been good enough for slide shooting. As you say, lower speeds are more easily made accurate as the shutter can be adjusted. the highest speed not so much as it relies entirely on the mainspring... But it is unlikely that even new it ran at the indicated fastest speed. I have a small collection of Compur mainsprings but would only use them if the spring was broken, not to attempt to get the fastest speed at that speed.

Synchro Compur wear

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