Hasselblad 500c and Phase One P45 Back - long exposure not working?

[kristyansen]

This and mristuccia's observations are interesting, as the 4/50, 3.5/60, 2.8/80, 5.6/120, 4/150 and 5.6/250 all use the same Compur shutter, in that you can interchange them between lenses. So the flash contact behaviour should be the same.

One thing to keep in mind is these older C lenses were used with +300V flash syncs, so the sync contact in the shutters typically shows arcing damage. These are inside the shutter, so the contacts are not easily replaceable, but for electronic flash, this is not usually a problem. Mechanically, the contacts close when the shutter opens, and open when the shutter closes. For electronic flash the 1st closing contact is all it needs, so damage/service/modifications to the shutter that did not maintain the sync contact while the shutter is open would not affect this function.

Hi @itsdoable this fits very well what @darr was saying on burnt PC-syncs - I am assuming since the Planar 80 was the standard lens, that this lens was really used intensively in past times including with flash, so more models may experience the same issue due to this... And yes, the flash sync itself works, does not need two operations (close / open) on the PC-sync contact.

 

[kristyansen]

If that's an old 500C body, does it have the sync port in the side of the body? If it does, that syncs with the rear baffles instead of the lens and might do the trick. Since it stays closed as long as the baffles are open, it should give the back the sync it needs. It doesn't matter if you are in long B exposures since there's no need to sync to the lens opening - the sensor is just on whilest recording blackness if the lens shutter isn't opened yet.

I never owned any of the chromey C lenses. I've always had at least CF, but mostly CFi, CFe, and F lenses. I've also never owned any 500/501 bodies. I've always had at least 503 bodies and a lot of 20x bodies. The 500c, some 500c/m, and I'm not sure on the 500cm had the body shutters (they were technically used for M sync, not the lenses X sync).

One thing about all of the C lenses (new and old) is that the sync contact are mechanical, and hence prone to oxidation/corrosion. They may close, but can get a high resistance. That is fine to "pulse" a strobe which is only looking for 100ms contact, but extended duration may result in loss of "sync" because the resistance is going up as the spring pressure equals out over a few seconds. The contact can usually be cleaned with something like some 10000-15000 grit material, like what we use to smooth out fountain pen nibs. It's like filing points on old cars to clean up the carbon buildup. I also tend to put a tiny drop of DeOxit red on the contacts to keep them from oxidizing further.

If you can get an ohmmeter and old sync cable, you can put it in resistance mode, cut the old cable and connect the meter across the wires (no polarity, just one lead on the center and the other on the shield), fire the lens and watch to see what it does. It should go down to < 1Ω and stay there. If it goes back open immediately, the contact are opening back up. If the resistance starts to vary, jump, or climb, it's most likely corrosion.

Thank you @docholliday.
Unfortunately the body sync contact does not work anymore - maybe it is also oxidized or just disconnected, as was suggested on the Forum - and I think indeed that would do the trick.
Regarding cleaning the PC-Sync contacts with grit material this can only be done by opening the lens by a specialist, and it cannot be done "from the outside"?
Also just using a bit of deoxit from the outside of the lens cannot work without cleaning the contacts first, correct? (I am just looking for the least invasive solution, which of course should also be safe for the lens).
I do not know a specialist in the area either, I would really have to do some research.

 

[docholliday]

Thank you @docholliday.
Unfortunately the body sync contact does not work anymore - maybe it is also oxidized or just disconnected, as was suggested on the Forum - and I think indeed that would do the trick.
Regarding cleaning the PC-Sync contacts with grit material this can only be done by opening the lens by a specialist, and it cannot be done "from the outside"?
Also just using a bit of deoxit from the outside of the lens cannot work without cleaning the contacts first, correct? (I am just looking for the least invasive solution, which of course should also be safe for the lens).
I do not know a specialist in the area either, I would really have to do some research.

Yes, unfortunately, this is one of those situations where a disassembly is required to reliably fix the issue. There really isn't a non-invasive way to fix the problem. Cycling the lens a bunch of times may temporarily get the contacts to work, but the second the humidity changes, it could quit working again. The M sync body contacts were usually problematic as they were never used much post flash bulb days. That neglect usually left them inoperable or intermittent.

Your best bet would be to upgrade to a newer gen lens, like a CF. There's always upgrading the back to one that doesn't use the sync, but rather the body "finger" that tripped the backs. The lens would be the cheapest, as the 80CF is easy to get a hold of.

 

[mristuccia]

Uhm, so far we have sampled three C 80 lenses having the same "issue" in this forum thread.
I now suspect this behavior may be by design on that specific lens model.
Unless we find at least one C 80 behaving differently as a counter proof.
By the way, mine is a black T* one.