[vicmortelmans]

Hi,

My LX badly needed CLA and I had it performed by Harrows Technical. The report said the following: "I noticed that when using auto and electronically controlled speeds using a dedicated Pentax flash unit only, the shutter locks up, I’ve tried using other finders but the fault remains so it is probably the main circuit board is in some way defective. These are not available but using non Pentax flash guns on manual mechanical speeds is possible."

Too bad, not having TTL flash anymore, but I could still use Pentax (or generic) flashes in Auto-mode.

Now, only a couple of months later, I notice another flash problem. With the exposure on manual (I was using 1/30 or X) and the flash on auto, the flash is firing, but the frames are underexposed. I did a visual check by looking through the shutter with the back open and indeed, I can't see the flash light coming through. So the flash must be firing before or after the shutter.


Would this be a mechanical problem, or another issue with the main circuit board?

If the board is deteriorating this quickly, I should be worrying about my metering as well? I know the metering in manual mode is quite different from the metering in AUTO mode. I have this optical test tool that you can plug in to the headphone socket of a mobile phone to test shutter speeds, but this won't help to test the AUTO mode, because the metering depends on a film being present

Why isn't there some Chinese factory that produces circuit boards for the LX ??

Best regards,
Vic

PS. I bought myself am MZ-5, so I can still enjoy my TTL flash and my lenses and I'm afraid the LX will see less use. With current prices I can't afford buying another one...

[ProfessorBuzz]

...but I could still use Pentax (or generic) flashes in Auto-mode.

What specific models of flash are you using? eg AF280T ?
What mode is the flash in vs the camera mode? e.g. Manual or TTL on the flash; X or ???? on the camera.
How is the flash connected to the camera? Side terminal or hot shoe?

Now, only a couple of months later, I notice another flash problem. With the exposure on manual (I was using 1/30 or X) and the flash on auto, the flash is firing, but the frames are underexposed. I did a visual check by looking through the shutter with the back open and indeed, I can't see the flash light coming through. So the flash must be firing before or after the shutter.

It's hard to see this visually, and with the back open, the OTF meter doesn't work, so not sure this is a good test.

Would this be a mechanical problem, or another issue with the main circuit board?

Could easily be an electronics problem or an electrical contact problem.
Or (forgive me) operator error.
Or camera and flash are just too old and worn out.

If the board is deteriorating this quickly, I should be worrying about my metering as well?

How old is the camera? 1980 vintage (42 years old) or 2001 vinage (21 years old). After 10 years, a lot of electronics especially capacitors fail... so everything is suspect. Metering can be checked against a reference grey card. Use 2 cameras with same lens under same light to compare, if you don't have a better way to check.

Why isn't there some Chinese factory that produces circuit boards for the LX ??

Can't be done economically, no market, components from 40 years ago aren't avaialble, and higher margins making other products.
Yep, it would be nice, we all have frustrations when things come to their end of life.


Let us know what your exact setup is per your earlier questions, and maybe we will have some ideas.

[gofour3]

Now, only a couple of months later, I notice another flash problem. With the exposure on manual (I was using 1/30 or X) and the flash on auto, the flash is firing, but the frames are underexposed. I did a visual check by looking through the shutter with the back open and indeed, I can't see the flash light coming through. So the flash must be firing before or after the shutter.

The LX flash sync speed is 1/75 second when you have the shutter speed dial on "X". Do you have a copy of the manual and looked at using the LX with non TTL flashes in AUTO?

Here is a link to the manual if you don't have one:

Pentax LX camera manual, user manual

Phil.

[vicmortelmans]

What specific models of flash are you using? eg AF280T ?
What mode is the flash in vs the camera mode? e.g. Manual or TTL on the flash; X or ???? on the camera.
How is the flash connected to the camera? Side terminal or hot shoe?

The first film that showed the problem was shot with a minolta flash in auto mode (= read the fixed aperture from the table on the flash for your ISO) --- I bought this particular flash because it allowed for higher aperture than Pentax's flash units, and I like the mix of available light with flash light). Camera was set to 1/30 for this film.


I tested a similar setup (see below) with a Pentax AF280T in auto mode (red setting) and 'X' shutter speed, because even with the flash in AUTO mode, I get a mirror lock-up when the LX is on anything other than 'X' shutter speed.

I checked the manuals of the AF280T and the LX and although there's strong suggestion to use the AUTO shutter speed setting also for a non-TTL AUTO flash unit, there's also a table that says you can use all manual speeds from X down to 4s for AUTO flash.

Actually, thinking about this, what difference would it make for the camera if you use a flash in AUTO mode (either Pentax's or generic) or in manual mode? Either way the camera must be set with the aperture that you read from the flash's back panel and some shutter speed slow enough for the shutter to be completely open.

And on my LX, the flash sync signal seems to be triggered before the first curtain opens, while in fact it should be triggered when the first curtain is fully opened.

It's hard to see this visually, and with the back open, the OTF meter doesn't work, so not sure this is a good test.

Am I not right that in manual shutter speed the OTF isn't doing anything? When looking through the shutter while triggering the exposure button, I could clearly see the difference between using my LX and my MX (same lens, same aperture setting, same flash settings). On the MX I saw the flash light, on the LX I saw just the available light, as with no flash. The flash fired in both occasions.

When I set the LX to some very slow speed, I can see that the flash fires before the shutter is opened.

Could easily be an electronics problem or an electrical contact problem.
Or (forgive me) operator error.
Or camera and flash are just too old and worn out.


How old is the camera? 1980 vintage (42 years old) or 2001 vinage (21 years old). After 10 years, a lot of electronics especially capacitors fail... so everything is suspect. Metering can be checked against a reference grey card. Use 2 cameras with same lens under same light to compare, if you don't have a better way to check.


Can't be done economically, no market, components from 40 years ago aren't avaialble, and higher margins making other products.
Yep, it would be nice, we all have frustrations when things come to their end of life.


Let us know what your exact setup is per your earlier questions, and maybe we will have some ideas.

The metering without flash on itself looks OK, comparing to other camera's, I mean: what the meter in the viewfinder tells the exposure should be. But for testing if the actual shutter speed is OK, especially in AUTO mode, I'll only be able to test this with actual film, I'm afraid?

I was also testing the shutter speed in AUTO mode without film, just on an auditive basis, and it was much longer than what the meter told it should be, but I read that's because there's no film inside, and the meter in AUTO mode relies on light reflected from the film, which is not the same as light reflected from the bare pressure plate, so that is definitely not a good test.

My only way will be, I believe, to abandon flash on my LX and to run a test roll and note down when I'm using AUTO and manual modes and check the results and continue from that...

Best regards,
Vic

[TwoUptons]

You can tell quickly if the auto setting on the camera is giving you something like the right shutter speed by listening...
1/2 s sounds very different from 1/30 s, for example, so you should be able to tell if the shutter is at least trying to do the right thing.
You may be able to tell the difference between 1/15 s and 1/30 s, but you can get an idea...

-Eric

[andrewd]

I was also testing the shutter speed in AUTO mode without film, just on an auditive basis, and it was much longer than what the meter told it should be, but I read that's because there's no film inside, and the meter in AUTO mode relies on light reflected from the film, which is not the same as light reflected from the bare pressure plate, so that is definitely not a good test.

Best regards,
Vic

That is normal. Mine does the same (also serviced by Harrow). It is because the reflectivity of the black pressure plate is way less than film. The camera exposes perfectly in auto mode. My Olympus OM4ti which also has OTF metering does the same thing.

[wkraus]

m I not right that in manual shutter speed the OTF isn't doing anything?

You’re perfectly right. Some people don’t read the posts they reply to.

I see no reason to assume the auto exposure wouldn’t work, but it is a good idea to test it the way you suggested.

[andrewd]

I was responding to the particular paragraph about the OTF metering in Auto mode, not all the other questions.

[wkraus]

I was responding to the particular paragraph about the OTF metering in Auto mode, not all the other questions.

I was not referring to you, sorry about the misunderstanding. It just so happened that my reply followed yours.