Mamiya M645 1000s PD Prism meter problem

Hi All,

 

I've just signed up to photo.net, and have also just entered into MF

world (although had a couple of box brownies and some other weird

looking 120 snapshot thing when I was a kid back in the 70's)

 

I've just purchased a Mamiya M645 1000s 90 model, complete with 80mm

1:1.9, 45mm 1:2.8 and 210mm 1:4, Waist Level Finder and PD Prism

Finder S, Metz 45CT-5 plus Sekonic Studio Auto II L-448 meter.

 

My PD Prism's meter has an issue, it reads overexposed all the time

when powered up (red led at top the only one that lights) regardless

of light in prism. The prism shutter setting works fine and I have

pretty much ruled out bad contacts. I have searched high and low on

photo.net and the net for someone who has found the same problem, have

found a handful of cases similar or the same, none had found the cause

of the problem.

 

I am pretty good at fixing stuff having spent years sorting out all

manner of mechanical and electrical items and working as an electronic

service tech for a couple of years, so if I could get my hands on a

factory service manual or relevant PD Prism pages, I reckon I could

probably work out what it is, even though I might not be able to fix

without parts, which may not be available any more.

 

In any case, does anyone know what causes this problem?

 

And can anyone suggest where I might find/download the factory service

manual or pages?

 

One last question (sorry about the long post and deluge of questions)

I plan on replacing the light seals on the back cover (breaking down

now)which would appear to be not too challenging, but what about the

mirror damping foam, can this be done through the front of the camera

without dismantling?

 

Any tips would be greatly appreciated.

 

Cheers,

 

Mark.

www.mamiya.com has a set of user forums and a section to download manuals. Unfortunately, it works only with Internet Explorer (with other browsers, the forum menu doesn't show up), so I can't check it from my Linux computer to see if that manual is there.

Thanks John, much appreciated. Have checked out the download secion before, it only has the user manuals, not the service manuals. All I really need to know is how to remove the knobs from the PD prism. I'm starting to suspect that the fake leather stuff on the knobs has to be peeled back to reveal some screws, can anyone confirm?

 

Mark.

Mark, you are right, you have to take the leather off from the speed and ISO knobs then you can remove these knobs, there are some screws.

To remove the prism release button you have to remove the plate that covers the contacts then at the other end of the release button inside the prism you find a small hole, you can put a kind of small screw drive inside the hole a,d turn the release button to remove it.

Tony, you're a star, that's the info I was after, couldn't find a trace of such info anywhere on the net about this prism. Didn't want to butcher the leather before I was sure the screws were under there as well. That prism release knob sounds a bit fiddly to release but I'll give it a go.

 

Certainly think there's something wrong with the electronics in my prism, not only does it only register the top red (+) LED but it does not switch off after 15 seconds as the manual claims it is supposed to. Hopefully it will be something simple like a cracked board or dirty/broken connection.