Weston Master V

[denishr]

I have several Weston meters, and since many of our RF cameras either don't have a meter, or their meters are dead, many of us use handheld meters.
One of the best (economy) options is a classic Weston meter. No batteries, good, sturdy design, and also historically appropriate for most of my RF cameras 🙂
My preference is Weston V, due to its large, easy to read scales.
Anyway, here are the three Westons that I have:

 

[denishr]

A good source of used Westons is the usual temple of our addiction 🙂 (read: eBay).
However, although many sellers describe their meters as "reacting to light", some will be inoperable. Sometimes the reason is a dead selenium cell, in which case you can't do anything. Well, you can: get a new selenium cell from Megatron in London, UK (which is what I did for my Weston V), or send it to Quality Light and Metric (I think that's their name, correct me if I'm wrong) in Hollywood, CA. Ask about the price first - I know they're good, but I don't know how much they charge.
If the cell is still reacting to light, there are a few things we can check to see if the meter can be brought up to specs. We need to disassembe the meter - not always easy. I hope the photos will help.

The tools required: nothing much - as seen in the photo below. The first screwdriver from the left has a "hollow point" (a DIY job, the center was filed a bit) - reasons will be clearer later in the sequence.
A rubber stopper or something similar, to help unscrewing the center screw on the dials, and a hex nut driver, for the two hex screws on the back.
Here are the tools I used...

 

[denishr]

Invercone

Invercone

BTW, if you're buying from eBay or other source, by all means try to get a Weston that comes with appropriate "Invercone" attachment. It's a dome which is used for incident measurement - very helpful, and difficult to find separately (not to mention that sometimes it costs as much as a complete meter!)
Here is the usual complete Weston Master V set...

 

[denishr]

Here's the invercone attached for low light readings (with light baffle open).

 

[denishr]

Now, let's get on with disassembly.

NB: the photos in this thread show disassembly of Weston V meter. Older Westons are pretty similar, so most of the stuff here should also apply.

We'll tackle the front first, to see if the needle is moving freely and to check that everything's OK.
First, unscrew the large screw in the center of dials. Use a rubber stopper or something similar to get a better grip - that screw can be tight after so many years. If you decide to use pliers, use some kind of rubber or other material on the jaws in order to avoid marring the screw.

 

[denishr]

Now the dials will come off. No springs, no danger of anything flying off 🙂
Note the "tooth" on the meter body and the appropriate hole on the dial back. They have to match when you put the dial back on.

 

[denishr]

Now we can go on and remove the whole front face.
The housing is secured by two "funny" screws, as shown in the photo below. You can also see the shape of the screwdriver point - the center has been filed away, so that it fits around that protruding center screw.

 

[denishr]

This is what we have now, and as far as we'll go.
I would not recommend any further disassembly - I haven't tried it myself. BTW, I had the selenium cell replaced on this particular meter by a pro - the repair person who usually works on my cameras. So, you won't find instructions on replacing the cell here....

 

[denishr]

Now is the time to check whether the indicator needle is moving freely, to clean any particles that might have gotten there, etc.
If the needle sticks, you can carefully bend it.

Check also whether all the screws are tight, and whether the "press-button" on the side of the meter frees and stops the needle movement as it should.
When that button is pressed, the needle moves freely. When it's not pressed, the needle is stopped in its movement by that long chrome "bar" over the needle.
Check it out, it's not that complicated. Maybe you'll have to adjust the "bar" a bit - at least I had to do that on my specimen.

 

[denishr]

Another shot from above - the chrome "bar" is clearly visible. Observe how it behaves when the "press-button" on the side (on top of this photo) is pressed. You'll get the idea. This is the usual reason for "jumpy" needle behavior. If the "bar" is not lifted high enough, the needle will stick.
You can also see the coil which drives the needle. You can carefully inspect it using a magnifying glass to see if the coil has been broken, etc. This could also be the reason for a "dead" meter. However, the wire is very fine, and I'm not sure you can just solder it back in place, without doing even more damage.

 

[denishr]

After having checked everything on the front, we can put it back together - in the reverse order.

Now it's time to check the back.
There's a potential problem here: the back cover is secured by two hex screws, which could be difficult to unscrew without proper tools. Hex nut drivers will come handy. If you don't have them, good tweezers may be of help. Be careful not to scratch the back cover (I wasn't 🙁)

 

[denishr]

In the center of the back cover you can see the "zero corrector", used for "zeroing" the meter. I.e. when the cell is covered/dark, the needle should go all the way to zero. If it doesn't, this "zero corrector" can be used to adjust the zero position.
Here you can also see the hex screws.

 

[denishr]

After taking off the back cover, you can check the condition of the meter needle coil and verify that the coil moves freely without obstacles. Also check the condition of the coil and the contacts.

 

[rover]

You know you made me go to ebay and look already.🙂

 

[denishr]

The light baffle, used for High/Low readings has two springs which actuate the hi/lo readout scale. If you take the baffle off, it can be tricky to get those springs back into the small holes in the readout scale contacts. You can use a wooden or plastic toothpick to help you position the springs. There's a strong magnet around the moving coil, and metal tools are not going to be of any help 🙂
The photo below shows the readout scale holes where the pointed springs go.

 

[back alley]

timely post as i have already been looking for a second meter.
it's just such a pain having to transfer my pilot2 from one bag to another. 🙂

joe

 

[denishr]

The light baffle removed - note the pointy springs which have to go in the holes as pictured above.

 

[denishr]

After checking the back and removing any obstacles and/or locating any possible problems, it's time to put everything back together.
When re-attaching the back cover, be careful to align the "nipple" on the back (back side of "zero corrector") with the appropriate lever on the meter body - the "nipple" goes in the slot, as indicated in red below.

 

[denishr]

BTW, you may have noticed my "DIY" calibration of the selenium cell.
The fact is that, after replacing the dead cell with a new one, the readings were too high.
So, after some trial and error, I found out how to correct that - with a small piece of black adhesive ("electrician's") tape. You need to find the right position and size and just tape it over the cell.
Ugly, but it works! 🙂

 

[denishr]

That's all, folks!
Any comments, suggestions, corrections, etc. are welcome.

These are very good, sturdy and surprisingly accurate meters. So, if you get one which seems to be "dead" or erratic, you can open it and try to find out what's wrong with it. I hope this little essay will be of help.

Denis