Quantum Calcu-Light XP succesfull repair

[navdra]

Maybe this will be interested to someone one day soon...

Recently I bought praised and very hard to find light meter Quantum Calcu-Light XP light meter. When I tried it out on a sunny day (and in lower lightning conditions later on), it seemed suspicious to me. I suspected it reeds too low. So I borrowed good working meter from my pro friend and it prooved that I was right. It read around 1 f-stop lower than it should. At first, I thought it needs re-calibration, so I contacted QLM, but they weren't eager to take it in and reccommended me to send it to Quantum. Quantum said that they stopped servicing them last year.

After some more thinking and looking at the meter, photo diode looked fishy to me. Quantum's support confirmed that it's corroded but didn't want to provide data about it, so I was on my own... Luckily photo diode search returned only few results and the first one looked exactly like the one I need. I checked the rest, but this is the only one that matches by size and description:

SHARP BS100C
http://www.datasheetcatalog.org/datasheets/90/123290_DS.pdf

This one is out of production, but there is lead free replacement BS100C0F available. Still very rare, though. Only place that I managed to find that stock them is Digi-Key:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=425-2447-5-ND

Digi-Key techs confirmed that these replacement diodes function in exactly the same way as original, so I decided to pay pricey shipping fee (at least I got the meter cheap - only $30!) and see if I'm lucky.

Anyway, I replaced diode and metering now coincides to borrowed meter and is very precise. Replacement itself is two minutes solder - resolder operation.

Check Before and After pics to see if your Calcu-Light XP qualifies for diode change...


Regards,
Drazen

 

[timparkin]

Calibrating Calcu-Light XP

Calibrating Calcu-Light XP

My Calcu-Light XP was reading one and two thirds stops under so I thought I have nothing to lose by opening it up. I tested each of the pots and found the one that set up the calibration. It's a simple tweak and I'm now back in sync with my Pentax Spotmeter.

You have to
Take the battery cover off and undo the screws.
Put the cover back on the battery cover with batteries still inside
Peel back the rear cover (glued on) try not to crease it, a smooth bend should be OK
Undo the two screws underneath the cover.

You should be able to access the blue pot with a brass screwhead that is at the bottom of the meter (there are four. Top left and top right and middle left. You want the bottom right one (see pictures).

Turn anticlockwise to increase your reading
Turn clockwise to decrease your reading

It takes about 2 or possibly three turns for a single number change (which is a third of a stop).

I can't post images here but if you search for this thread title on apug or largeformatphotography forum you'll find some..

 

[ChrisPlatt]

I have an original model Calcu Light that has missing segments in the LED display.
Maybe I'll try poking around inside mine; I've got nothing to lose...

Chris