Gossen Lunasix Lightmeter Repair

Lunasix Lightmeter Repair.


I happened to snap this foto of my desk yesterday while aiming to fix a malfunctioning Lunasix that i had found in the odds and ends bin in one of the downtown photoshops here in Copenhagen, for a pittance. So I thought perhaps someone would like to hear my modus operandi?

First inspection revealed that the glass cover over the scales and meter needle was displaced by pushing it inward against the scales. So it would obviously be necessary to remove the cover. (Glass seen upper right)

To that end you firstly remove the thin alu plate covering the bottom of the Lunasix (seen bottom left). This is done easily, as it is only secured, or rather unsecured, by three dabs of glue.

Under the cover are 6 brass screws. But you only have to remove the 4 screws, one in each of the corners. The top plast cover then lifts off easily.

The misplaced glass windown is then removed , cleaned and replaced/secured with a bit of ordinary glue.

In my case, the meter needle was slightly crooked in the lower end, but which was quite easy to straightened out.

Be careful with activating the meter with the cover off, as a few parts may jump around. You can however safely activate the battery control buttom.

This showed the meter to function in a somewhat correct way, and I therefore replaced the cover.

Comparing the readout to that from my Gossen Luna-Lux indicated everything to be just about right.

(Apologize for the poor photo, I only took this one picture.)

That shop wouldn't happen to be Photographica? ;-) Those two trunks are a little too alluring.

Answer me this, is it normal that the internals (PCB and scale) shifts a bit when you press the button?
I see you have the model 3 (rocker switch) but it also seems to be the case on my original model.

They are very sensitive and usable light meters still despite their age, and also quite exquisitely designed.
I'd go through the hassle of fixing the shifting if it was possible, if only for cosmetic reasons.

Is there anything inside, rubber washers or fragile plastic posts that could have deteriorated or snapped?

I guess the PCB is held in position by the two lower screws as can be seen on the photo (I have not yet fiddled around with my sample...) Thus maybe these two screws have loosened.
A ultimate solution would be to fix the PCB to the casing by two drops of hot-melt. If necessary they could easily be removed again.

Helge said:

That shop wouldn't happen to be Photographica? ;-) Those two trunks are a little too alluring.

Answer me this, is it normal that the internals (PCB and scale) shifts a bit when you press the button?
I see you have the model 3 (rocker switch) but it also seems to be the case on my original model.

They are very sensitive and usable light meters still despite their age, and also quite exquisitely designed.
I'd go through the hassle of fixing the shifting if it was possible, if only for cosmetic reasons.

Is there anything inside, rubber washers or fragile plastic posts that could have deteriorated or snapped?

Click to expand...

Hi, Helge (and AgX). Yes, indeed, it might well have been found in said, alluring trunks. However I seem to remember always to have experienced a slight shift in the meter needle when applying or rather releasing the button. The lower end of the meter needle is held in pressure between the two transverse bars seen under the meter body (you only see one here, though, the other beeing hidden). If these two thin metal bars are not perfectly parallel, I think the shift may occur. Like in this one. If you have 'magic hands' you just might remedy any skewness, however slight in these two thin bars. But you would have to try it out yourself. It absolutely easy to take the cover off of the body. The PCB is held in place by 2 screws seen when you remove the thin botton plate (they are not seen here, as I said there is 6 screws under the botton plate, and only the 4 in the extreme corners hold the cover in place. The two others secures the PCB). One of these was loose in my sample, which might result in a slight shift of the scale? It's the first one I have pried into, so of course I don't know too much about it.

Thank you for the thorough answer. I'll post pictures and result of I ever get to it. ;-)

From the photo it seems the window pane had been glued in place by some brown rubber cement. I got countless cameras where that stuff lost tack to one of the surfaces (typically experienced with labels and covers).

I'm not sure which type of glue was used, and don't really remember precisely how it looked. But the glass was also secured with four points of 'hot-melt', of which one was broken, however.