Olympus OM1n Q?

dugrant153 · May 21, 2013

Hey all, so I've been using my late uncles om1n recently and it was really clean when I received it a few years ago. So clean, in fact, I have recently begun to wonder if it was CLA-Ed before he passed away.

The prism has no foam rot and is actually surprisingly clean given its age. But the glue holding the "film type paper slot" thing on the camera back was starting to rot and I had to tape it back on.

What's really puzzled me is finding an epx 625g battery in the battery compartment, which is an (up to date) 1.5v cell battery. I think the old mercury batteries ran at 1.35v?
Any way to tell if the battery compartment has been upgraded up to take on newer non-mercury batteries? If so, this camera may have been CLA-Ed is what I'm thinking.

RH Designs · May 21, 2013

If a 1.5v battery is put in an unmodified OM-1(n) the meter will be a couple of stops out (well mine was, anyway) so that might be a way to tell.

mr rusty · May 21, 2013

The prism has no foam rot

how do you know? What condition are the door foams and the mirror bumper foam pads in? any stickiness at all, and I would get them and the mirror done. Re meter - check with a new 1.5v battery and see if the meter reading is correct with another meter. If it is, it may well have been modified inside. usually the mods are to take an SR44 silver cell and include a spacer to take up the gap for the smaller battery. The 625 isn't so good because it is an alkaline cell not a silver cell and the voltage isn't very constant as the battery ages, unlike the SR44.

oldlincoln · May 21, 2013

OM1n's do not have the foam rot problem. I don't know what S/N the change was made but some very late OM1 MD's don't have the foam sealing around the prism either. This change applied to the 2's also. I have modified many OM1's for 1.55V batteries by placing a germanium diode biased forward in the battery circuit under the bottom plate. The battery compartment was modified with a Nylon ring so the SR44 battery would fit. However the S625PX can be used if you want to leave the battery compartment alone.

mr rusty · May 21, 2013

OM1n's do not have the foam rot problem

I do not believe this is correct.

John Hermanson posted on apug (forum search)

Yes, every OM-1, 1N, 2, 2N I see now for overhaul need new foam at the hinge, slot and mirror areas. John, www.zuiko.com

If John says all OMs need mirror foam, they all need mirror foam!!

baachitraka · May 21, 2013

CLA at any cost, so it may survive for another 10-15 years. Have fun!!!

oldlincoln · May 21, 2013

I need to clarify what I wrote about foam rot. I meant to say that the prism damage that occurs on OM1 and OM1 MD cameras will not happen to the n variants because they are not foamed there. All of the foams ( not the silk cord) used on camera seals and mirror bumpers (and elsewhere) in the late `70s and in the `80s has rotted. Classic audio equipment buffs have found that the same urethane formulas were used for many loudspeaker surrounds and they are all goo now.

darinwc · May 22, 2013

mr rusty said:
I do not believe this is correct.

John Hermanson posted on apug (forum search)

Yes, every OM-1, 1N, 2, 2N I see now for overhaul need new foam at the hinge, slot and mirror areas. John, www.zuiko.com

If John says all OMs need mirror foam, they all need mirror foam!!

That does not mention the prism foam. This was foam used internally between the prism and the top cover. You cannot see it unless you remove the top cover.
As the foam ages, it turns to goo and that goo eats away at the silvering of the prism.

Yes, past a certain serial number they stopped puting foam between the prism and the top cover. I'm not sure where the cutoff date was.
But, like Schrödinger's cat, you wont really know until you look.

mr rusty · May 22, 2013

John Hermanson wrote:

My repair database shows OM-1 chrome ending around 1,593,xxx. The 1N
starting around 1,644,xxx. The start of 1N production also signaled the
start of the factory using prism foam again.

OM-1 were made with no prism foam from (approx) 1,119,xxx (3/77) through
1,623,xxx (11/78).

FWIW I had the prism changed on my OM1n due to foam rot when Mke Spencer CLAd it.

Olympus OM1n Q?

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