Canon AV-1: Seal on the
Very much so!
It's a very common problem with older cameras and is an irreversible breakdown of the foam which was used to provide light-proof seals on the camera back and also to cover the pentaprism and provide a mirror buffer. (The pentaprism and mirror buffer are part of the viewfinder system).
The first problem is that when the foam turns to goo it allows light to leak into the camera and spoil the film, but that's the least of it. Where it gets serious is that the goo spreads inside and can gum up delicate moving parts; worst of all the goo is somewhat corrosive and can damage the coatings on the pentaprism leaving permanent residual ghosting images in the viewfinder.
The good news is that it's a well understood problem and every professional camera repairer can remove the goo and restore the camera as part of the regular service that all SLR's should periodically undergo. The foam will be replaced by modern materials which do not degrade. Some repairers also replace the mirror buffer, others will just remove the old foam and omit the buffer, but I always insist on a new buffer. At the same time, the repairer will give the camera a thorough CLA service (Clean, Lubricate, Adjust) which for a camera in non-professional use will often see it through a few more years, but I'd recommend getting a CLA done annually if you're well off and every couple of years if funds are tighter. The CLA will also ensure that the light metering is correct and on cameras using the older 5.4v mercury oxide (PX28) batteries can include a meter recalibration to allow use of modern 6.2v silver oxide (4SR44) equivalents as the mercury cells are no longer available. (Some folks use 6v manganese dioxide [PX28A] batteries, but they start off at a voltage slightly higher than 6v and constantly drift down with use to below 5v, so metering is nneither consistent nor accurate). A regular CLA with foam removal costs a bit more than a regular CLA but is a once only expenditure. Some repairers charge for recalibrating the meter for 6.2v, but most won't if you politely explain that you can always take the camera elsewhere.
DIY kits are also available and some are very good indeed, but they can be fiddly and messy to fit and none of them address the more serious issue of the pentaprism. In practice, repairers will remove the old foam from the pentaprism but almost never fit a replacement. It's not strictly necessary and the reluctance to fit a replacement stems from the risk of further damage to the pentaprism by the adhesive. The outside of the pentaprism is normally painted black from new, but foam goo usually attacks the paint and partially removes it. it also attacks and removes any optical multicoatings on the prism. When this has occurred there is no fix: the problem will not worsen once the foam has been removed but there will be residual damage visible in the viewfinder as ghostly dull patches, but this is something which can be tolerated and will not affect image quality.
If you want a cheap quick fix, then use a q-tip (UK= cotton bud), a wooden cocktail stick/toothpick and some alcohol to remove all visible traces of gooey foam. Omit the mirror buffer altogether and take your chances with the prism foam. To replace the rear light seal just use a length of woollen yarn: you'll find that if you twist it slightly it will reduce in diameter and allow you to press it into the slot where the foam was using a toothpick. Usually you can get away without gluing it, but if any glue must be used then use a few very sparing dots of something easily removed such as Copydex or the rubber cement sold for repairing bicycle inner tubes. At the hinge end of the camera back will be a thicker, wider bit of foam. Just use a few dabs of glue or to secure a good thick double or even triple width of yarn. The fix isn't a professional one, but it's good enough and was how the seals were made before rubber foam was invented. It also buys you the time to decide whether you like using the AV-1 enough to invest in a professional CLA with the additional options.
I hope that my reply has given you a few options and will enable you to get your camera into working condition again. All I ask is that you return the favour by taking a moment to rate my answer.
Jan 05, 2010 |
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