[TorontoDave]

Hi all! Wondering if anyone has any advice on this. The TTL meter on my 67 will work fine for a little while, but after a few minutes it won't turn on any more. The only way to fix this is to detach and reattach the lens. I've tried a bunch of things including: toggle the auto/manual switch on the lens, ensure meter is switched off after use, try different apertures, try different shutter speeds, try manual mode, ensure contact points are clean. None of that fixes it. I've tried detaching and reattaching the TTL finders without the lens attached. Works for a while after putting the lens back on but stops working after a while. Also, I've tried detaching the TTL finder with lens attached and can hear the spring loaded part snap back (i.e. confirming that it had still been correctly engaged). Nothing seems to work except detaching and reattaching the lens.

Detaching and reattaching the lens seems simple but in practice it is super annoying when you're about to take a picture and realize that you need to put the camera down in your lap and do that.

It's one of the later TTL finders that just say "Pentax" on it.

I have a feeling there's no solution for this but maybe someone has some insight into the problem. Thanks!

[tuco]

When the meter goes off again, toggle the on/off switch and rotate the aperture back and forth from wide open to stopped all the way down to see that does anything. When you remove the lens, the aperture chain moves all the way in one direction (as if you set the lens to f22). And when you mount the lens it moves back to whatever aperture the lens was set at. That is the mechanical interface between the TTL and the camera body. The electrical is from contacts on the body and prism. It doesn't hurt to rub them clean now and then.

[gofour3]

The electrical is from contacts on the body and prism. It doesn't hurt to rub them clean now and then.

Yep that would be my advice as well. Also check the prism foam seal, as it may be worn out. If the foam is bad and the prism is not fitting properly, the electrical contact will be flaky. I had to replace the foam on one of my prisms, there are kits available if needed.

Phil.

[TorontoDave]

When you remove the lens, the aperture chain moves all the way in one direction (as if you set the lens to f22). And when you mount the lens it moves back to whatever aperture the lens was set at. .

On my 67, the chain position at f22 is not the same as when the lens is removed. At f22, the chain is already pulled part way. On my 55mm lens, the chain is out about half an inch at f22, and on my 105mm lens the chain is out about a quarter inch at f22. Only removing the lens fully releases the chain. Is this not right? I've tried the suggestion of toggling on/off and moving to f22 and back, but no dice... Only loosening the lens (fully releasing the chain) seems to do the trick, and it works every time.