Swapping selenium cell between Weston II and V

Has anyone successfully swapped the Selenium cell out of a Weston model II or III into a Weston V?<p><br>

I have a few Weston II and III meters that work perfectly but are a bit tatty. I also have a few "dead" Weston Vs where the crappy later Selenium cell has low output. I even have one that looks mint, complete with invercone, box and instructions. The cell's still dead though.<p><br>

I have experience taking these meters apart, but it's not something I'd do without good cause. So does anyone know if the good ol' cells are the same size and have a compatible output to the model V cell?<p><br>

I'd really like a fully working Weston V. I think its looks and ergonomics are superb. Shame about the cheapo cell that Sangamo/Ilford fitted to it.<p>

BTW, I'm not interested in buying a new replacement cell. By all accounts they're just as rubbishy as the original Weston IV, V and Euromaster cells. If not worse.

Personally, my choice is not to touch them.

My understanding is that they use amorphous selenium on an iron substrate, with a thin gold electrode in front. It has to be thin enough to let enough light through, but thick enough that you can make contact with it. I suspect that the failure is in the contacts to the iron, and especially gold.

I have a Canon VI, which originally had the usual coupled Canon meter, but that one died many years ago. I believe my father tried unsuccessfully to fix that one. I got another one a few years ago, which works some of the time, and when it isn't, a light tap on the side sometimes restores it.

Hello everyone. I like Joe have a slug of tatty, but working, II or III's and would love to swap out their cells into a few NFG V's. From what info gleaned from Quality Light & Metric's, the cells are no longer being manufactured.

Could their be a techie-freak person somewhere within these forum that could lead us to installing some type of silicon cell into the meter & adjusting the simple bridge circuit these metesr use? My Gossen Pilot I / II meters work nicely, but I do enjoy the Weston feel & action. Perhaps a cell, type unknown to me, from that unit ? Aloha, Bill

I might just try the swap anyway. I have a Weston V minus cell waiting to go.

As far as I can remember, the cells both have the same contact configuration; an annular metallised ring on the front and metal substrate. It's just a case of seeing if the size and electrical output are the same.

There was a thread somewhere else on reviving selenium cells. Someone recommended baking the cells in an oven to de-oxygenate the contaminated selenium. That sounds like last resort stuff to me, given the toxicity of selenium. Personally I'm not too keen on handling the cells at all except with latex gloves on!

I'm not sure the cells are gold flashed. The industry standard for transparent conductive coatings is tin. That's what's used to pattern LCD displays and the like.

Now everyone went and did it! Having to take a look--and with a perfectly functional Weston V--the thing came apart. I have wanted to clean and lube the scales for some years now--and the plastic ferrule which holds the needle release button was cracked.

PM is now done! If the physical alignment of the cells from a II or III are the same--you may have a winner. Looking at the internals of the II, that may be the case. The III is a bit tapered at the top, and this may be an issue. What is common is that the main internals of the II appear identical to the V. Another option is the much maligned model 560 (or aka 6) produced under license from Schlumberger and made by god knows who. BUT the internals appear identical to the V--the major difference being the plastic case and sliding diffusion grate. These are pretty dependable though--and maybe one with a broken glass can be had for cheap.

The biggest question is whether the electrical characteristics are the same. There was little bit of improvement on the sensitivity over the years--and the electrical characteristics may be a bit different between cells. Remember that calibration is a match between the output/resistance of the cell, and the resistance/reluctance of the coil in the D'Arsenval movement. One can pad this with a small potentiometer if necessary. Seeing as mine works perfectly, I was not even remotely interested in measuring the cell's resistance--even with my VTVM which has 10Mohm of isolation...

The favorite transparent conductor is indium tin oxide, ITO.

It is, for example, used to warm the windows of supermarket freezers so they don't frost up,

and I believe also for LCDs.