My experience with Polaroid 900 shutter

[murrayatuptowngallery]

I thought I'd share my Polaroid 900 shutter exploration in case it's

of interest to anyone and maybe someone else can answer my questions.

 

I got one on eBay to experiment with...might put a Universal Press 23

sheet film spring back on it...or something else.

 

Shutter acted very strangely, so with the help of another member here

I opened it up.

 

4 Phillips screws around back of lens will free up the bellows. I had

to carefully free the vinyl that was aggressively stuck to the

lens/shutter body.

 

3 straight slot screws accessible on the back after removing bellows.

Lens/shutter should be free from the lock at the front of the bed so

you can lean it forward. This allows removal of the front plate with

one lens element. For those interested it appears to be a slightly

negative diopter element.

 

I removed the screw holding the ASA/EV dial so I could see a

retaining screw underneath. Two problems here. The screw screws into

a Delrin or nylon gear. Don't lose either one. Make note of the dial

position, or better yet, rotate it to one extreme AND make note of

it's position. Apparently only screw compression holds it where it

belongs and I have to figure that out again.

 

There is a flex circuit from the photocell down to the battery

compartment. There is a pin that the flex circuit sits on about 1/2

way down. Lift that up & there is a screw holding the shutter plate

to the captive portion of the shutter body. I dropped the screw & it

didn't hit the floor. I think it's stuck to the magnet of, of all

things, a light meter D'Arsonval movement on the back side of the

shutter.

 

There are about 5 moving parts in the shutter/aperture combination

mechanism. I could see that the last piece to move wasn't closing so

my shutter would open and not close. I couldn't see any springs

broken. I was about to give up & realized that the rubber plunger

(kind of like a cylindrical bellows) Polaroid used on some old

shutters (for vacuum?) was not extending all the way. The folds were

stuck together. I carefully unstuck them and now the shutter operates

(no idea about timing).

 

Someone warned me I might need to replace a capacitor due to aging. I

don't see any. I also don't see an electromagnet. There is something

attched to the photocell with a 4 digit number on it I assumed was

resistance. I haven't measured yet to check. It could be a

coil/electromagnetic. With no capacitor my wild guess is that they

use an RL time constant. I will have to explore the black object with

the 4 digit number more.

 

I cleaned the battery corrosion with table vinegar. Mercury battery

construction shared electrolytic similarities with alkalines.

 

Now I have to find the missing screw & try a battery.

 

What I could use help with is identifying the proper position of the

EV/ASA dial at one extreme of rotation.

 

I thought the shutter speed range was 1/12-1/600 second. It seems to

go much slower if one dials well below EV 10. The dial will go well

below 10 and well above 23 (interesting).

 

It would be interesting to know if 'bokeh' fans see a difference

between the 900 and 900/160/150/95B type. The lenses are supposedly

the same, but the iris shape is not. The non-electric eye group had

round apertures except some are a little weird at EV 10, with one

flat side. The 900 iris starts out round at EV 10, ends up square at

EV17-23 and in between is an ugly jagged 4-point starlike thing.

[david_m]

Fascinating stuff. I have been experimenting with the lens in the 150 and 800. They have mechanical shutters and good quality 3-element glass lenses 130mmF8.8 I believe.<div></div>

[murrayatuptowngallery]

Thanks for the reply. I was hoping I wasn't the only one interested in such things, but that is often the case with strange pursuits I involve myself with...makes for some lonely threads.

 

Murray

[murrayatuptowngallery]

Are you using the camera body with lens still attached or putting the lens/shutter on something else like a view camera w/ground glass?

 

Murray

[400bpm]

Thanks for the post Murray. I'll probably be doing this in the near future "just for fun" so thanks for providing a roadmap for me. I took the back off of an 800 recently just to see what was going on in there. Took a sec to clean the lens but was mostly just impressed by all the little springs and stuff back there. I'd never taken apart a shutter or lens assembly before. I remember seeing the ugly jagged thing, too, on my 800.

[murrayatuptowngallery]

I thought the 800 type shutter had a nice set of round apertures & a odd shape shutter blade, but the 900 really looked worse to me. Maybe Polaroid actually made sure the exposure rate was even as the shutter/aperture mechanisms traverse the lens...taking efficiency and evenness of exposure into account.

 

BTW, I had emailed you at your COE address a while ago. I'm a little slow - I finally figured out what COE was...I thought it was just a server name.

 

Murray

[minhnguyen9113]

Hi Brian and Murray.

 

I did play with several Polaroid 900 and found out it is not worth to fix the 900 with the electrical problem.

1) can not get parts

2) get parts from another 900 doesn't make sense

3) 50% of the 900 have mechanical problem, and after mechanical related fixed, 50% of them have electrical problem.

So after you get a 900 check to make sure if it mechanically work, if it is, try a battery to make sure the electric eye responses to light, if it does you have a good camera, if not use it as a manual camera, do not waste time. I did spend time to fix the them and now I rather buy another one to save time and money. If the bellow is bad I convert to different formats with box like one Gene took pictures and posted on this forum. Good luck

[minhnguyen9113]

Hi Brian and Murray.

 

I did play with several Polaroid 900 and found out it is not worth to fix the 900 with the electrical problem.

1) can not get parts

2) get parts from another 900 doesn't make sense

3) 50% of the 900 have mechanical problem, and after mechanical related fixed, 50% of them have electrical problem.

So after you get a 900 check to make sure if it mechanically work, if it is, try a battery to make sure the electric eye responses to light, if it does you have a good camera, if not use it as a manual camera, do not waste time. I did spend time to fix them and now I rather buy another one to save time and money. If the bellow is bad I convert to different formats with box like one Gene took pictures and posted on this forum. Good luck

[murrayatuptowngallery]

Thanks Minh.

 

I'll wish myself luck. If it works, price was OK, if it's just manual, I already had enough other ones (800,160,150,95B) :O)

 

It DOES display a variable shutter speed manually now (actually conspicuously longer than 1/12 second too), and if I dial all the way below EV10 it will stay open until the shutter is released (not how B is intended to work on this).

 

I had hoped to get a verbal description from someone about where the dial gets aligned relative to full CW or CCW to get me close.

 

I may have to recalibrate it afterward.

 

Murray

[minhnguyen9113]

The B setting being used for time exposures in manual mode only.

When taking pictures with the 900 in electric eye mode, you shouldn't cock the shutter more than 5 sec or less than 3 sec before strip the shutter. 1) To save battery life, when you cock the shutter the electric eye start working. 2) the electric eye need at least 3 sec to receive power from battery and become stabilized.

That is advanced technology in the beginning of the 60's applied to electric eye on Polaroid cameras.

[david_m]

You are much better off using the mechanical shutter off of the 150 or 800. If you want an electric shutter, the one on the colorpak cameras powered by two AA batteries is very reliable.

[murrayatuptown]

Wondering if anyone still finds these posts useful, I realized I just did. I searched and found my own forgotten thread.

 

So I'll update it.

 

1) I have experimented with 95/150/160/800 style shutters to understand how they work. Repeatedly cycling them while watching can allow spring retainers to creep out of position until the spring flies across the room! The shutter cocking spring is the first to go and the B/I (Bulb/Instant?) spring. So beware. I left one springless specimen permanently open, glued an M42 extension tube to the back & used it on at least one digital camera. Awaiting an M42/E-mount adapter this week to try it on another. Some would say (not ask) 'what's the point?' I like the images I got enough to keep doing it. Like Bart Simpson burning his hand on the stove...ow...ow...ow...

 

2) The 95/150/160/800 shutter (I haven't looked up a proper name for this kind of mechanism as I like my analogies...pinball-machine-shutter, time-of-flight-shutter, etc.) If yours bounces open a couple times after firing, it's because a small piece of foam rubber at the end of the shutter's at-rest position has decomposed. IIRC, it's inside a helical 'bumper' spring. I think there is also a magnet to capture it also. I tried various types of foam...too thin and it bounces. Too thick and it doesn't close all the way. What worked best for me was the really thin sheet wrap foam, probably no more than 1/16" (1.5 mm) thick. I used a folded piece about 1/8" (3 mm) wide, maybe 3/8"-1/2" (~9-12.5 mm) long. Not critical...the attempt that works it the one to use. Watch out for springs creeping out while testing this with the back half of the lens/shutter cover removed. (Implied steps are to remove and retain the screws holding the bellows to the rear shutter cover, which has one lens element attached, then remove the 4 (?) screws holding it to the rest of the front of the camera which serves as a combination of front 'standard', lensboard and shutter assembly).

 

3) If you have cameras with shutters of this type screwed up by previous invaders, or suffered the above calamity during your own investigation, and resign yourself to a permanently-open specimen for digital camera usage, you can just pivot the shutter plate slightly open and use a piece of tape or contact cement to make it stay open. Both are more or less reversible.