Olympus OM-1n CdS cell

[Buko]

Hi,
I have been enjoying my little Olympus for nearly 3 years now, but only aproximately two years ago, when I started developing film by myself I've realized that the exposure meter was aways overexposing by 2-3 stops. Therefore I started using an external meter, but for street photography I find it wery inconvenient. Finally, a few days ago I decided to try solve the problem:
Following the instructions on the original repair manual have taken off the top cover and the pentaprism and I've noticed that one of the CdS cells, the one on the left looking from the back of the camera, is not responding to the light.
I took the cell out of the camera, but now I don't know how to replace it. I tried put in a cell from another camera but it does not fit in.
Is there any way to find a new cell without disassembling another OM?

 

[mcfingon]

Most likely the over-exposure was caused by using a modern 1.5 volt battery instead of the original 1.35 volt one. It will cause 2-3 stops error even though the voltage difference is only 0.15 of a volt. There are two cures for that behaviour. One is to get a modification made to the circuitry near the prism to lower the voltage being received at the light meter cell. The other is to get a voltage lowering adapter that reduces the 1.5 volt battery output to 1.35 volt. I have just ordered one of those for my OM-1 via eBay: https://www.ebay.com.au/itm/New-MR-9-Battery-Adapter-the-Solution-for-Discontinued-Mercury-Battery-PX625-JP/172974391896?hash=item284613c258:g:M1EAAOSw8XBZtiRc:rk:47😛f:0

 

[Chriscrawfordphoto]

Most likely the over-exposure was caused by using a modern 1.5 volt battery instead of the original 1.35 volt one. It will cause 2-3 stops error even though the voltage difference is only 0.15 of a volt. There are two cures for that behaviour. One is to get a modification made to the circuitry near the prism to lower the voltage being received at the light meter cell. The other is to get a voltage lowering adapter that reduces the 1.5 volt battery output to 1.35 volt. I have just ordered one of those for my OM-1 via eBay: https://www.ebay.com.au/itm/New-MR-...=item284613c258:g:M1EAAOSw8XBZtiRc:rk:47:pf:0

Higher voltage batteries cause underexposure on the OM-1. He will need the adapter you mentioned once he repairs the camera, but his testing shows one of the camera's meter cells is dead. It'll still be dead no matter what power source he uses, so that needs fixing first.

 

[Beemermark]

Unfortunately it seems that the OM-1 and OM-1n are very prone to dead meters. I've never had an issue with the Om-2 and 2n series. I think the OM-1n and 2n were introduced in the same time frame if memory serves me correctly. So why does the OM-1n still use a mercury battery while the OM-2n uses a silver oxide battery?

My advice, if you want a working meter, is to ditch the OM-1 and buy a 2n. They're cheap enough.

 

[p.giannakis]

I wouldn't ditch the OM-1 for that reason. In the pre-'n' versions, the majority of the non-working meters are due to a nylon screw that keeps the battery chamber in place. That screw breaks and then the battery does not make proper contact.

A non-working meter in a 'n' version is probably corrosion somewhere in the wiring. I had three OM-1 so far (one plain and two 'n') all with dead meters and were all repaired with a CLA.

 

[Buko]

Most likely the over-exposure was caused by using a modern 1.5 volt battery instead of the original 1.35 volt one. It will cause 2-3 stops error even though the voltage difference is only 0.15 of a volt. There are two cures for that behaviour. One is to get a modification made to the circuitry near the prism to lower the voltage being received at the light meter cell. The other is to get a voltage lowering adapter that reduces the 1.5 volt battery output to 1.35 volt. I have just ordered one of those for my OM-1 via eBay: https://www.ebay.com.au/itm/New-MR-9-Battery-Adapter-the-Solution-for-Discontinued-Mercury-Battery-PX625-JP/172974391896?hash=item284613c258:g:M1EAAOSw8XBZtiRc:rk:47😛f:0

I don't think this is the case. I used the right batteries and I'm pretty sure the proplem is one CELL stopped working, because when the light hits the other cell the needle moves, but when the light hits this one the needle doesn't move. Moreover meter overexposes more than just 2-3 stops… more like 3-4.

 

[Buko]

I wouldn't ditch the OM-1 for that reason. In the pre-'n' versions, the majority of the non-working meters are due to a nylon screw that keeps the battery chamber in place. That screw breaks and then the battery does not make proper contact.

A non-working meter in a 'n' version is probably corrosion somewhere in the wiring. I had three OM-1 so far (one plain and two 'n') all with dead meters and were all repaired with a CLA.

It seems that in my camera that screw has been already changed with a metal one.

 

[Beemermark]

Try http://www.zuiko.com/web_5__20150924_016.htm, slows pair of cells for $20