Home
SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Asahi Pentax LX 'Sticky Mirror Syndrome'
View previous topic :: View next topic  


PostPosted: Fri Jul 03, 2020 4:16 pm    Post subject: Asahi Pentax LX 'Sticky Mirror Syndrome' Reply with quote

hi All --- I have two Asahi Pentax LX one bought 1987 the other a free gift from Pentax House ( RE -- the Famous FIRE Story) BOTH have the infamous 'Sticky Mirror Syndrome and both had exposure troubles!
I have cured the Exposure Troubles by Rotating the Exposure Compensation and ASA dials back and forth as on the ME Super, to clean the contacts underneath and both agree with my Weston Master V and on film gave good exposures now BUT the 'Sticky Mirror' drives me Nuts ! I had a look -- there are two very small 'Mirror Rests' , slightly different from 1987 model to the later model -- could i put a very small amount of Iso-Propyl Rubbing Alcohol OR Lighter Fuel ( Butane) on them to see if it cleans off any 'sticky' surface ?


PostPosted: Fri Jul 03, 2020 6:23 pm    Post subject: Re: Asahi Pentax LX 'Sticky Mirror Syndrome' Reply with quote

pentaxpete wrote:
hi All --- I have two Asahi Pentax LX one bought 1987 the other a free gift from Pentax House ( RE -- the Famous FIRE Story) BOTH have the infamous 'Sticky Mirror Syndrome and both had exposure troubles!
I have cured the Exposure Troubles by Rotating the Exposure Compensation and ASA dials back and forth as on the ME Super, to clean the contacts underneath and both agree with my Weston Master V and on film gave good exposures now BUT the 'Sticky Mirror' drives me Nuts ! I had a look -- there are two very small 'Mirror Rests' , slightly different from 1987 model to the later model -- could i put a very small amount of Iso-Propyl Rubbing Alcohol OR Lighter Fuel ( Butane) on them to see if it cleans off any 'sticky' surface ?


Don't know LX, you probably already know:

Sticky-mirror on Spotmatics due to gummy foam mirror bumper cured by replacing the bumper foam.

Alcohol or butane (and lighter fluid) can dissolve foam iirc.

Alternately clean mirror back side, especially where 'Mirror Rests" touch.


PostPosted: Sat Jul 04, 2020 12:06 am    Post subject: Reply with quote

I prefer to scrape the old foam off, I use dental picks or plastic cocktail sticks. Dissolving the foam with alcohol is messy, especially in the lens chamber - the dissolving goo gets everywhere.


PostPosted: Sat Jul 04, 2020 1:47 am    Post subject: Reply with quote

Lloydy wrote:
I prefer to scrape the old foam off, I use dental picks or plastic cocktail sticks. Dissolving the foam with alcohol is messy, especially in the lens chamber - the dissolving goo gets everywhere.


Like 1 Thank you!

Yes, not as way to remove the foam, or to try to clean off sticky, avoid the dissolving goo! After the foam is gone clean off any residue, alcohol &lighter fluid are great for that, drop or two on earbud.


PostPosted: Sat Jul 04, 2020 8:13 am    Post subject: Reply with quote

the Mirror Bumper FOAM is still good so the mirror does not stick on that-- it takes about 4 seconds from press on release button for the mirror to move UP and Shutter to work.


PostPosted: Sat Jul 04, 2020 11:00 am    Post subject: Re: Asahi Pentax LX 'Sticky Mirror Syndrome' Reply with quote

pentaxpete wrote:
...there are two very small 'Mirror Rests' , slightly different from 1987 model to the later model -- could i put a very small amount of Iso-Propyl Rubbing Alcohol OR Lighter Fuel ( Butane) on them to see if it cleans off any 'sticky' surface ?


Apparently you have to be careful with the mirror rests, as reducing their thickness can alter the angle of the mirror and provide for false focussing. By how much I don't know, but obviously enough to be an issue. Either replace them, or dry them up with talc or graphite powder (pencil lead filings will do), or some-such, on a cotton bud. I'd have the pipe on the hoover running close-by too, as I remember the mirror box on those is not a place to be careless.

Please note I've not tried any of the above, Pete. Just read it in passing. Personally, I don't like the idea of talc. Surely, it will make a hard surface that will flake when the mirror starts pounding it.

This fella did a home replacement -

https://www.dpreview.com/forums/post/17482780

Two LX's. Some people are just born lucky! Wink Good luck whatever you try.


PostPosted: Sat Jul 04, 2020 1:32 pm    Post subject: Reply with quote

I have to say this - I own hundreds of cameras, probably over a thousand, I've replaced mirror foam on untold dozens. I've seen "mirror sticks to the foam" thing once. What I am saying is - if mirror sticks up, it is almost invariably something under the hood.


PostPosted: Sat Jul 04, 2020 4:25 pm    Post subject: Reply with quote

Pete, when I bought my LX some years back, not only did it have the sticky mirror, but even more annoying, it had the focusing error that Sciolist mentioned. Mine was caused at least in part by one of the rests being completely gone. I had my local pro camera repair place fix it and they did a good job. Before having them do the repair, I did quite a bit of searching on the web to see if it was something I could do, since I've repaired cameras before, but after reading up on it a fair amount, I decided that I didn't have the tools for the job, so I turned it over to the pros.


PostPosted: Sat Jul 04, 2020 4:40 pm    Post subject: Reply with quote

So far I'm lucky as they do NOT have any 'Focus Shift' . When I exercised the shutter on the 1987 one it started working better .


PostPosted: Wed Aug 05, 2020 7:56 pm    Post subject: Reply with quote

I luckily got one complete LX with a sticky mirror and one body for parts, as the shutter is out of order.
The mirror hesitated for seconds to move up before the repair. The main cause is a rubber bumper on the left side (looking from the front) that is used to damp the slap of an arm moving the mirror. This is mounted with small excentic screw to the side of the mirror box. You need to remove the lens mount to get access. I removed and cleaned out what was left from this bumper and replaced it with a tiny o-ring (3x1mm). After re-assembling I discovered that the bumper bottom left (again looking from the front) was sticky and holds the mirror when it should move. The mirror slides backwards and then moves up. The stickyness wouldn't let it slide. I replaced the bumper with a tiny piece of rubber (1.5 x 2.5 mm or something and 1.5 mm thick). After that you have to adjust the mirror angle. Study the two screws that hold the arm with the bumper. I did this by trial and error and it is now spot-on.

I had no means to apply the stuff to make the body dust and water resistant again, but that is not strictly needed.

I'm very happy with the result! My advice? Go for it! Work very precise, make notes and lots of pictures. BTW, due to a smartphone crash I lost my pictures...


PostPosted: Thu Aug 06, 2020 8:39 am    Post subject: Reply with quote

YO !! Very helpful BUT since I wrote the story the shutter blinds on my 1987 LX have seized up - one does not 'cap' with the other any more, leaving a gap . I have tried pulling it across from inside body but it springs back un-capped again.


PostPosted: Thu Aug 06, 2020 11:16 am    Post subject: Reply with quote

What a pity! The for-parts camera had that issue. Nothing to loose, so I tried to remedy that. When you have removed the lens mount, you see the strings (! yes strings, not tape) that should pull the curtain, left from the mirror box. These string. may get of the spindle. I succeeded with the use of pick tools and a lot of luck.

Don't know if it was sheer luck or that it is something most people do with ease.

Regards an good luck!