I did a search of the whole forum group for input about fixing a Weston Master II light meter, and found nothing about disassembly and repair. Before that, I searched on the internet and found several results, both pages and threads in forums. A few pages have commentary and photos. That helped with disassembly, and general info about these meters. I had been wanting one, and finally bought one of two at a flea market in Berea, Ky. I think they had been there a year maybe, and were still there when I went last week, after reading more about them. Both seemed to operate about the same, and both were deficient, but I took a chance and bought one, for $10 plus tax. I had already read that a selenium meter, the selenium part, can deteriorate over time, and these are old, made from 1945-1953. That is for the Master II.
In the store, I took both to the front window and checked the light readings. Neither would do anything with the baffle closed. With the baffle dropped down, which is for low light situations, neither would do much. They went up to less than 6 on the low number scale, mostly less than that, 3.2 or so, but they went up a little higher some times, depending on just how I aimed them. Sun was out. I picked one of them as being slightly better and bought it. I was gambling on the fact that other people had acquired old Master light meters that barely worked, and after being exposed to light for a while, days or weeks, they revived. I read this in multiple places. I'm not sure how much time it would take to revive one, if it can be revived. I had my meter with the baffle open, and exposed to light for about 3 days. Sometimes I shined a flashlight right at it to see what it would do; did that to start with, afterward now and then. No change.
I looked again for info and found a posting in some forum in which the guy said that he has worked on several of them, a bunch maybe. He said that most people tend to think that the selenium part needs to be replaced. He found that with most of the ones he dealt with that it was a matter of a dirty contact, or more than one. He had cleaned one or more contacts and then a meter would work again.
I didn't want to wait 3 weeks, and mine didn't seem to be getting any better, so I decided to take it apart, partly at least, and see about cleaning any contacts I could find. There are a few pages on the internet that show a meter in various stages of disassembly, both the Master II, and a Master III or IV. A couple of them show the Master II.
Here are some photos of mine, in disassembly:
The back removed.
I'm not going to get into the details of disassembly. That can be read on other pages.
Front cover off. Those hand written numbers were already on there.
On both sides of the armature or whatever, where the needle is attached, there are two bolts. These are electrical connections. I undid both and did some scraping with a knife, in case that might help. It didn't. I also removed that double ended copper connector and scraped on that too. It all looked good, but I scraped anyway. No effect. There are two wire "stops", left and right, for the needle. I marked their positions on the plate that has "135" written on it, before I loosened those bolts.
I'm not sure, but I think this meter has been worked on before. That metal plate has a date written on it, 1-19-60. As far as I know, it was made no later than 1953. The selenium "cell" is under that plate, and I decided to uncover it and see what the disc looked like. Somewhere in this process, I accidentally bent the needle upward, but I later bent it back down to normal, and it looks ok.
Disassembled.
That copper star looking thing is a spring apparently, to keep a little tension on those parts. It is copper, I believe, so that it is non-magnetic. There is a magnet below the needle. That disc is the selenium coated item.
The selenium disc.
That arrow points to a contact place, where the disc contacted a wire. The spot looked to be a bit corroded, and I thought that might be the problem, or main problem, so I rotated the disc so that one of the other clean gaps would be in its place when put back in. Got it all back together, and found no change. Rotating that disc didn't help.
Apparently, the selenium is degraded much and won't do like it is supposed to. One person who got into this said that selenium "is nasty stuff, be careful with it." What I found on my disc is dry; looks like dry paint, is dry to the touch. I wiped it with some wadded up paper towel. Nothing came off, not even dirty film or whatever, nothing.
I know very little about selenium cells and meters, only what I found out during this inquiry. It is expensive to send a meter to a repair shop. The disc can be replaced with a new one, as far as I know. I guess some repair people are still doing that, but it is costly, so I read. If I could get a disc, I could fix mine. They probably cost plenty. I have a cheap meter that I bought in the '90s I think. It works, but I wanted a Weston meter, one with more to it. It doesn't work. My other meter that works has the light receptor part at the end, not on a flat side.
Update: After lunch, I took the meter outside to see how it would do in the sunlight. It was on a window sill, with the baffle down. Was overcast. Outside, with the baffle down, the needle got up to 6.5 at a precise position, toward the sun. Still not good, but I think that is the highest it has gone. With the baffle closed, the needle registered a little when aimed at the sun. I don't think it did that before. I put it back in a window sill, to leave it the rest of the day.
