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06-11-2019, 10:22 PM   #1
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Ghastly foam.....

Does anyone know if Pentax routinely used the dreadful dissolving foam inside cameras other than for light seals.

I recently took a K1000 to bits and found none, there was a small foam bumper underneath and to the front of the prism but it was immaculate and didnt need changing. It had a different consistency to the stuff that dissolves into tar.

I am loathe to try and get the lid off my KX as I havent found a guide and I dont know what may lurk beneath its film speed dial.

Much is talked of Olympus and their love of packing the drek distilling foam around prisms, and I have cleaned up two OMs just in time but recently I took a Canon FTb cover off and found that it too made use of the horror foam, luckily Canon had put a plastic cover between the foam and the prism, judging by the damage caused to metal parts which had come into contact with the dissolving foam I doubt the prism would have survived had it not been shielded with a plastic cover.

Recent reading suggests Nikon used this foam in some of the F finders so I am anxious as to whether Pentax used it. I would hate for much loved KX to be on the receiving end of degenerating foam.

Anyone know ?

06-12-2019, 04:08 AM   #2
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I have a KX with de-silvering of the prism, which I suspect is caused by foam. I've found foam to do this on some Canon and even Leicaflex SL, so its clear the industry wasn't aware of this characteristic back then.
06-12-2019, 08:12 AM   #3
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For some reason Pentax used a pinkish/cream coloured foam as a gasket around the prism edges on the Spotmatics. Presumably it helped keep dust out of the gap between the prism and the focusing screens. Of course it turns to goo, and is a nightmare to clean off the focus screen or prism if you have to get in there.

But the worst is that foam bumper found on top of the prisms in the later K1000s (Chinese production especially). These cameras are now 20+ years old, and the foam degrades and eats its way through the prism silvering. That said, a lot of materials used to hold down prisms in lots of cameras are prone to eating through the prism silvering - but I think those late K1000s hold the record for speed.

My advice is to anyone with a K1000 apart is to replace that pad with something a bit more durable and remove the old adhesive off the prism top. It's getting hard to find replacement prisms these days - and a little ironic that more than once I have had to replace a '90s K1000 prism with a salvaged Spotmatic prism!
06-12-2019, 10:48 AM   #4
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Thats odd my Pentax K1000 had no foam on top of the prism, just a pair of springs attached to a metal frame, ther was a small white coloured foam pad just underneath and to the front of the prism that showed no decay at all.

My K1000 is a made in Japan version so maybe that explains it.

06-12-2019, 11:26 AM   #5
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Pentax started using tape and foam as a cost reduction measure which later caused prism problems.

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