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Geschrieben von: drew (at) rileyelf.co.uk   
Freitag, 22. Februar 2008 um 22:22 Uhr
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Praktica B series disassembly
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After buying a cheap Praktica BC1 for spares on Ebay I thought I would share with the world what I have learned about them.

The reason I bought the BC1 was to provide a particular part for my partially non-working BCA. The fault with my BCA was that the auto winder would work with it. It turns out the fault was in the base of the camera. A lttle operating peg was missing, this peg operates a leaf switch that in turn switches the winder on.

 

Peg should be there...

So off to Ebay and £5 quid later I was the proud owner of a non-functional BC1.

While this was being delivered I got impatient and fashioned a new opeating peg out of a drawing pin. So when the BC1 arrived I thought I would have a look at it and try to figure out what is wrong.

The fault with the BC1 is that it does not wind on. The lever moves and makes all the right sounds and feel but it will wind on again with out releasing the shutter, and when the shutter is released it only makes a tiny click and the shutter blades just jump a little.

So first the bottom cover came off (four tiny screws) When winding the film on everything looks OK, put as the winder lever is released, the cranks and levers inside return to original position. IE they are not latching in the cocked position. If I hold the main crank down in the cocked position and fire the shutter it fires correctly. Given the huge complexity of the cranks and levers in this area I decided not to investigate more as the chances of getting all the levers, cranks and springs back in the right place would be very slim indeed.


So I wondered if the fault may lie under the top cover, so partly for the sake of curiosity and partly for the challenge I decided to take off the top cover.

I have take a few cameras apart, this one proved fairly difficult.

First off, open the back and hold the rewind rod still and unscrew the rewing knob. Now pull the rewind rod down into the camera and remove.
Under the rewind knob is a slotted plate, this needs to be unscrewed, you could make up a special tool for this, but I used a fine screwdriver and little tack hammer to gently knock it loose. Unscrew the plate and it will come off with a large spring beneath. Now the ASA ring assembly can be removed.
Now on to the rewind lever, Turn the camera over and you will see a screw on the underside of the rewind lever, remove it and the plastic cover will come off. Holding the rewind lever down is a nut, unscrew this and remove the shakeproof washer and lever.
Under the lever you will see another slotted ring, again you can either fashion a tool to suit or gently tap it loose with a small screwdriver and small hammer.
Now the hotshoe should be removed, to do this you first need to remove its cover plate and shim. The cover plate is hooked into a recess nearest the front of the camera, simply lift this front edge with a tiny screwdiver and slide the plate and shim back. Under the plate you will find four screws, remove them (note, two are shorter, make sure you note where the short ones go) The hotshoe should now lift off.
On the subject of the shutter speed knob. This SHOULDN'T need to be touched. I removed the top cover and undid the two screws beneath, this was a mistake. These screws hold the knobs brass bearing plate in the right place. This meant it was a sod to get it all in alignment when I re-assembled it.
In theory the shutter speed knob should come off with the lid and its little operating peg should pull straight out of the plastic cam beneath.

But I digress.. The cover itself can now be unscrewed. The cover has two screws on the back, one either side of the prism boss, one under the ASA knob. The cover should now lift off exposing all the electronics.


BC1 open

As it happens there was no fault under here, so I put it all back together and surprisingly the fault still remains.

If anyone reading this actually knows how to fix my fault I would be very grateful to hear from you.

Re-assembly is (in time honoured tradition) the reverse of the dissasembly.

As always YMMV and don't shout at me if you trash your camera.

Have fun
Drew (drew (at) rileyelf.co.uk)

new version of this article: Praktica B series disassembly

Zuletzt aktualisiert am Freitag, 22. Februar 2008 um 23:41 Uhr
 
 

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