Jupiter-9 M42, how to access the front group

ludoo · Expire: 2011-12-05

I have an M42 J-9 I got in a trade a while ago which has a loose front group (the one right behind the front element), and I have absolutely no idea how to get to it. In the following picture, I have already removed the focus helicoid, the front element, and the back group, the assembly pictured is the aperture mechanism (black housing protruding towards the back), the preset ring (aluminum ring in the middle), and the black housing that keeps the front group (black housing towards the front). The group seems to be sandwiched between the two black housings.

I think the screw labeled with 'A' should come off, it's the one transmitting movement to the aperture mechanism, but unfortunately it's stuck. I already loosened all the grub screws I could find but they do nothing, they only let the top brass ring (right above the alu one) rotate freely but it makes no difference. Any ideas how to open this thing further so that I can fix it, and finally use it?

ludoo · Expire: 2011-12-05

After a couple of hours of fighting Russian design, I can answer my own question: the top black housing is made by two parts, which sandwich the front group. The parts are held together by the small grub screw labeled as B, and it needs to be almost completely unscrewed before you can start unscrewing the two parts.

I had to completely dismantle the lens before noticing how the front group was held in place, and in the process I: had to file the stuck screw labeled as 'A'; partially butchered the large brass ring held by 'A' so that I could unscrew it after filing; lost the tiny grub screw 'B' on the floor, but managed to find it again. Smile

The aperture assembly is now soaking in lighter fluid as the inside of the lens was completely covered by yak oil, which migrated everywhere. I'll reaasemble it tomorrow and try to find a way of replacing the filed screw, Ill probably solder something on it. I can't wait to use this lens.