davidsimon

Update: blue and orange wires to the CDS were soldered to the incorrect contacts (according to the wiring schematic) I've swapped these over but no change to the meter behaviour, which is not too surprising as the CDS is basically just a variable resistor right? Perhaps the CDS is malfunctioning, I do get a change in resistance through it when varying the light input, but only a very small change. What should the resistance range be on these things?

Not sure if this is the right place to post this, but I could use some advice on repairing the meter on my Auto S3. I've fully stripped the camera and isolated the meter circuit (photos attached), there are clear signs of previous repairs, I beleive someone has added in a new variable resistor as shown in the attached. My confusion is in determining the correct values of these resistors to make the circuit function correctly, the S3 repair manual doesn't go into this level of detail. When the battery is installed, the meter immediately jumps to F16 (no light on the CDS). Adjusting the variable resistor to its minimum resistance and shining light on the CDS caused the meter to move back down to around f8, but no further. This seems backwards, more light should move the needle up not down? I've checked the circuit against the S3 repair manual and all seems correct. I've checked all wires and all are reading zero resistance (so seemingly no corrosion). The battery contacts are in good condition and polarity is correct. All soldering is good at the CDS contacts in the lens. Can anyone recommend a sequence of testing that would identify the issue?

 

 

 

I've checked what you describe, and yes when looking through the viewfinder, changing the aperture on the lens does affect the light meter and does change the shutter speed. So for example, at f1.8 the meter indicates a shutter speed of 1/125 but actually fires at around 1/15th. Then when the aperture is changed to f8, the meter indicates 1/30th but the shutter fires at around 1 second!

That's my understanding too, and the problem is that I did have a film in the camera at the time of testing!

I'm having some issues with metering in auto mode on an OM-2. The problem is the actual shutter speed during exposure is much longer than the shutter speed indicated by the meter. For example the indicated speed might be 1/125 but the actual shutter fires at around 1/15th or slower (judging by ear).

 

Here's what I know so far:

-Viewfinder metering is consistent between auto and manual modes.

-Viewfinder metering is consistent with my DSLR at the same ISO/Aperture, therefore the issue must lie with the actual shutter speed being selected by the camera.

-My testing was done with brand new silver oxide cells fitted and film loaded.

-In manual mode, shutter speeds sound about right (by my not-so calibrated ears)

-I replaced the mirror stop foam as it was a bit sticky.

 

My initial conclusion is that there is a problem with the two SBC blue light sensors in the bottom of the mirror-box, which I guess must be reading incorrectly and causing the slow shutter speeds? I checked if they were dirty, one had a little dust but gently cleaning it made no difference.

 

I did also notice that the Manual/Off/Auto switch on top of the camera is a bit tempremental, and sometimes requires a wiggle to make contact at the chosen setting. Could this be the cause of the auto-mode issue (doesn't seem likely though)?

 

So my question is, what is the next step in my investigation? I understand there is variable resistor under the mirror box which controls the SBC metering circuit, would it simply be a case of adjusting this to correct the speeds, and is this easily accessible under the mirror box base? Otherwise, are there any other common faults here that I can check for?

 

For info, I'm fairly competent at basic camera repairs and have tackled some pretty challenging jobs on other cameras. I say this because I'm keen to try and get this repaired myself, however I will submit to a professional repair if it's out of my reach.

 

Any advice is greatly appreciated.

Hi All,

I'm trying to repair an AE-1 (non-program) with a faulty meter. Upon half-pressing the shutter release the meter bottoms out every time, regardless of camera settings or the amount of available light. After trawling the forums it seems the issue may be with the PX1 IC light sensor behind the prism, perhaps through bad solder connections?

 

I've removed the top cover to inspect, and from what I can see the surface of the sensor looks dirty or possibly corroded (photo attached). And indeed when I shine a bright light directly on to the sensor, I do get some movement in the meter needle through the viewfinder. So I've concluded that the sensor is indeed working, but just not very well, probably due to the surface dirt/corrosion. So my question is, what next? It doesn't look straightforward to replace the sensor, so can I instead compensate for the poor sensitivity via the series of galvanometers above the prism? How would i go about this? Or is there a technique to revive the sensor?

 

I guess it would help if someone could point me in the direction of a service manual for the camera, despite a lengthy search I've been unable to track one down.

 

And finally, this isn't a valuable camera and I'm not looking to buy another. I'm just too stubborn to let it die without a fight.

 

Thanks

 

I just bought a rather splendid OM-1n off the 'bay and it came with this rather nifty replacement battery compartment pre-installed, which is perfectly sized for a pair of SR44W's, and also swaps the battery terminal to the opposite side for easy installation of the required voltage dropping diode. Does anyone recognise this new compartment and advise where I can get more of them? Perhaps it's been cannibalized from a different camera, I'm not sure. Its the neatest upgrade I've seen so far on one of these lovely cameras.

 

<p>As far as I understand the whole idea of using soda for the blasting is that it won't damage the substrate. That's the theory anyway, I'll put it to the test in a couple of days. </p>

<p>Mathew, can you tell me more about the method for alkali stripping. Is it the same setup as for chrome de-plating? I've got some caustic soda here, would that be suitable? And for an electrical charge I'm thinking a car battery would work? The chrome removal setup has the camera part as the anode, and something steel as the cathode, would this work?</p>

<p>Ordered some bulk soda off the internet last night, should be here in a couple of days. The blast cabinet is taking shape, it's based around a plastic crate, with the addition of arm holes, access hatch, and internal lighting. Sounds much like the one Rob was describing above. And yes, I was thinking about picking up an air reservoir for the compressor. </p>

<p>Great tip about the acetone, I'll make sure it's the pure type and not the nice and gentle finger paint type.</p>

<p>I have to say I'm dubious about acetone, given the range of chemicals I've already attacked it with. But....I'm happy to be proven wrong. I'll pick some up in the morning and give it a try...watch this space.</p>

<p>Gus, thanks for the word of caution. I've already started work on a blast cabinet to contain the mess. After years working in the offshore industry I have a healthy respect for safety and tend to err on the side of overcautiousness.<br /> I totally understand your point on the value of original paintwork, and I agree. The thing is, the camera's I'm abusing are not high value collectables and as such their value is not my focus. I'm really just mucking around with a few ideas for now. So don't worry, no Leica's are under threat from my antics.</p>

<p>Well guys, it's been a successful day since my first post this morning. I started researching soda blasting and came across this link. I must admit I was dubious, but read on....<br>

http://www.aircooledtech.com/tools-on-the-cheap/soda_blaster/<br>

So, I gave it a go....<br>

First of all here's my bodged blast gun which I hooked up to my not so awesome compressor in the garage:<br>

<img src="http://d6d2h4gfvy8t8.cloudfront.net/17489187-md.jpg" alt="" width="680" height="510" /><br>

I don't have a tank on the compressor so I could only get short blasts of high pressure air, then wait for the pump to recharge the lines - not so awesome. But......having "borrowed" a small tub of baking soda from the kitchen, I was impressed with what it managed to do:</p>

<p><img src="http://d6d2h4gfvy8t8.cloudfront.net/17489186-md.jpg" alt="" width="680" height="510" /><br>

This was as far as I got before the soda ran out. Admittedly it's only a start, but a good start nonetheless. Next step is to order a big bag of baking soda (yet to source) and cobble together a wee blast cabinet so that I contain the mess and hopefully re-use the medium a few times. I'll report back in a few days with the results.<br>

The tumbler idea might be good also, if the soda doesn't work it'll be my next avenue. Sadly (or gladly perhaps!) there's no such thing as a gun club here in the uk, our government don't trust us with them, but I'm sure there are some rock polishers out there who might have the necessary vibratory contraptions.</p>

<p>Thanks for the feedback,<br>

Jeff, my reason for stripping the paint is to subsequently re-paint, so my goal is as good a finish as I can get. I think the best way to do this would be to completely remove the original paint. As you rightly mention, the main focus is the top and bottom plates, which I've completely removed from the camera's and subsequently stripped of all buttons/dials and plastic parts. The ideal scenario would be a dip'n'strip chemical which I could dunk the parts into and pull them back out as nice shiny brass. I do realise that these would probably be some real nasty, toxic, carcinogenic type chemicals but I am geared up to deal with that. What I'm unsure about is which chemical I need and where I can source it? <br>

I'd never heard of soda blasting before but after a bit of reading it does sound like a good solution. Unfortunately it looks like a few hundred pounds investment to get myself kitted out (which wouldn't be worthwhile for me) but I've made enquiries with some pro's to see what the costs would be. I'll also look into hiring it, but I might be struggling up here in the Scottish highlands!</p>

 

<p>Hi,<br>

I'm looking for some advice about removing the original black paint from some old SLR's from the 70's and 80's (Canon, Praktica, Olympus etc). Does anyone have any experience of successfully achieving this? (please don't respond telling me not to do it, it's not what I'm asking!)<br>

Here's what I've tried so far:<br>

Heat gun and soft wire brush - extremely slow and potentially damaging to the brass underneath.<br>

Nitro-mors - no effect<br>

Paint Panther (from tool-station) - no effect<br>

Oven cleaner - no effect<br>

Brake Fluid - no effect<br>

Fairy Power Spray - no effect (the modellers recommended this one)<br>

Cellulose thinnners - no effect<br>

I'd rather avoid using sandpaper as this will damage the brass underneath and give an uneven surface, which now leaves me out of ideas. Are there any chemical strippers out there which would manage this. I'm not entirely sure what the original coating are, some kind of baked enamel I'm guessing, but whatever they are they seem extremely resilient.<br>

Any advice would be greatly appreciated.<br>

Dave</p>