Sekonic L-8 repaired

[ctrout]

A friend gave me his old Sekonic L-8 the other day and I discovered that the amplifier was working but the cell in the meter was not. He had specifically told me not to sell it, keep it for myself. I was planning on using it with my Pentax K and SV, and with my Mamiya RB67. I was disappointed to discover that the meter was not responding to light.

I searched online for a while, looking on repair or disassembly information but found nothing so I decided to just give it a shot and see what happened. There was some kind of compound covering the screws that held it together. I thought they were just covered with rubber plugs or something but when I started to pick at them with a dental pick, I discovered that it was a clay like compound that crumbled away as I scraped at it.

With the three screws exposed I was able to disassemble the meter quickly and without any issues. The selenium cell was easy to access with only the metal frame that holds the diffuser, the clear plastic honeycomb lens, two plastic pieces that appear to be shims, and a metal contact holding the cell in place.

Once I removed the cell, I found that the metal contact is what was soldered into the meter's circuit and that it received current from the cell only through pressure contact with it, The same was true of the back of the cell and a copper contact point. When I removed the front contact, I saw that there was a framed area around the outside edge of the cell where the cell contacted the metal frame that was soldered into the metering circuit.

Since the meter is old, I considered the possibility that the contact areas between the cell and the rest of the circuit had become oxidized so I gently scraped the bright area around the edge of the cell, the corresponding area on the metal contact piece, the back of the cell where it contacts the copper, and the corresponding area on the copper contact piece. I reinstalled the cell and the meter immediately responded to the room lighting.

Now I just need to confirm the accuracy by using the meter to determine and set the exposure on one of my digital cameras and then, if it passes this preliminary check, test it with film.

 

[Sirius Glass]

That is great! I have been unable to find selenium cell replacements of any size today. I have a tiny light meter on my Tessina that I would love to get back in working order.

 

[Dan Fromm]

A month or two ago I had a chat with George at Quality Light Metric about repairing a meter that used a CdS cell. Not in his repertoire, sorry. In passing he mentioned that he could no longer get Selenium cells for Weston meters. No longer made and stocks are exhausted.

Against that, Ian Partridge http://ian-partridge.com/lightm.html seems to have new cells for Weston Masters, might be able to get cells for other meters. Certainly worth asking.

OP, I fully understand that your meter probably doesn't need a new cell.

 

[Sirius Glass]

A couple of years ago I called George at Quality Light Metric about repairing the meter that needed a Selenium cell. He gave me the bad news then.

 

[paul ron]

If QLM can get them, so can you. He must be buying cells from someone...or the replacements are silicon or another photovoltaic material.

I wonder what the rating is of the original cells?

.

 

[ctrout]

When I first opened the meter, it was my plan to measure the cell so I could try to find a PV from a solar calculator or something to drop in its place. Once inside, what I found led me to try cleaning the contacts and it worked. It did look like it would have been easy to retrofit a pv cell to wirk though. The only concern I would have is over calibration but I would suspect that a variable resistor installed in the calibration circuitry would probably do the trick.

 

[AgX]

There was a manufacturter of custom made Selenium cells. They have stopped that operation some years ago.

The alternative substitute could be a silicium cell.

 

[Sirius Glass]

Change to a different cell type would change the electrical properties and then the circuit would have be redesigned. A different cell type would not work that same way plus the color response would be different.

 

[paul ron]

maybe. gotta die trying.

 

[ctrout]

So I finally got the time yesterday to get the meter out and play with it a bit and it seems to be pretty accurate although it meters a bit differently than the meter in my 5D3. I metered several very different scenes and manually set my 5D3 to the indicated exposure and made the shots. I checked the histograms and all of the shots that I took were close enough to correct exposure that post processing would have easily fixed any errors. I'd say thay I was within a stop in either direction and any errors were more likely attributed to the lack of spot metering and picking up too much dark or bright areas.

After I confirmed that this meter delivers accurate readings, I got out the RB67 and started shooting. It's going to be a while before I will be able to develop the film but I'm pretty confident that I'll have well exposed, useable images.

 

[paul ron]

ooooh you're guna love the negatives n your prints will blow you away!

glad to hear your luck fixing that meter. after reading your adventures i opened an old dead weston. i had to remove everything to get to the cell. i resoldered the white wire and cleaned tye grounding metal back that rests in its carrier. still dead as a door nail when i put my vom on it.

if i had some stats of the original i would pop in something to replace it with close stats.