Hi, I was able to get this pretty expensive spot meter (to use with analog cameras) pretty cheap, but after about a year of use, it failed on me.

It always emitted a high pitched whine, which I wasn't sure if it was normal or not, but after using it in -25°C weather the display started showing very low contrast (barely readable from a normal viewing angle).



I took it apart and found a couple leaked capacitors and was able to replace them just fine. The PCB had very mild corrosion, which I treated and tested all the affected traces for continuity.

Now the meter powers on fine without any whine whatsoever, but the display still shows very low contrast. I've looked at the datasheet for the LCD driver IC (Hitachi HD61602H) and to me:
VREF1 ~5V
VREF2 ~5V
V1 ~ 4.5V
V2 ~ 3.5V
V3 ~ 2.5V
seem fine. Is there anything obvious I'm missing?

I don't see any variable resistors on the LCD board:





but one of the other two has a couple:




I'm not sure what they do so I've left them as-is.

Here is a link to the datasheet. I've also added a photo of the third board as well as a screenshot of the datasheet/my readings in the attatchments. Many thanks in advance!

 

Hey! Love the thread here. I'm actually having a similar issue on my own meter and was curious how you were able to get it apart? I have removed 5 screws so far but the top section is stuck. Any advice here?

 

I have removed 5 screws so far but the top section is stuck. Any advice here?

I'm still on holiday but I didn't want to leave you hanging... I don't remember everything because it's been about a year or so since I took the meter apart intitially.

Have you tried taking apart the flash socket? The "weird" screws are around the flash and the tripod screw. Other than that I think the rest were very visible from the outside, no sticker-peeling necessary.

 

It's been 2, almost three years! Phew. I finally got up the courage again to fix this, and I'm happy to report I have a working light meter again!

After reviewing the HD61603 datasheet again, I found out that the contrast is set with the circuit shown in Figure 22, Option (3) for 1/3 and 1/4 Duty Cycle Drive. Most importantly, there is a note that explains the contrast can be set with R5.

I desoldered R5 (marked R122 on the PCB) and measured 10KOhm. I replaced it with a 20KOhm trim pot temporarily and cranked up the contrast until the contrast was barely too high, then dialed it back down half a turn:

Just FYI check the inner display to make sure it looks good as well. I landed on a value of 3KOhm, but I'd highly recommend testing this out for yourself if anyone attempts this:

With that done, I desoldered the trim pot again and put a 3K resistor in its place permanently:


Closed the meter back up and everything is working perfect again!



Also, for completeness:

I have removed 5 screws so far but the top section is stuck.

The housing has 8 screws in total, three inside the battery compartment, two around the 1/4 thread at the bottom of the meter and 3 last screws under the hotshoe, which are hidden and protected by the hotshoe metal cover. You need to pry it out carefully.

 

oh wow! i was about a week away from ripping mine open and trying to figure this out for myself, great timing on that reply! did it fix the internal lcd too? my external one is still quite reasonable while the internal one looks like yours originally did.

 

That's too cool! I thought it would be a waste of time typing up my solution, bit it only took me a couple minutes and it's so often there's forum threads with the exact problem you have... but no solution. I'm very happy even just one person read my new comment

On my meter the external display was easily readable much earlier than the inner one. It maybe takes some more fine-tuning because it's backlit. I definitely think it's worth a shot in your case, maybe you don't need to go so extreme with the resistor (from 10k to 3k seems like a lot in my case).

Best of luck and please report back with your findings. And replace those caps as preventative maintenance too