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Old August 8th, 2008, 11:57 PM   #1
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Cleaning the Letus Mini

Hi guys,

My letus mini has 2 specs of dirt on the glass.
I can zoom past it when shooting, but it'd be good to get the wider field of view back.

Any recommendations on cleaning?

Thanks.
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Old August 9th, 2008, 12:28 AM   #2
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Kevin.


I have not dismantled the Letus Mini so my following comment should be regarded as a very general guide only.

If the Letus "Mini" is constructed so that the front comes out of the tube with the groundglass and motor attached it will probably slide out when the screws which hold the lens mount into the front are fully removed.

If the Letus "Mini" is constructed similarly to the Letus "Extreme", then screws which attach the front tube to the flip enclosure, when removed, may allow the tube with the lens mount screws undisturbed and the mount still attached, to be withdrawn forward over the groundglass and off.

My Youtube clip in this case is now quite old and should be regarded as a very inaccurate example of the general operating principle of these adaptors.

http://www.youtube.com/watch?v=yugfv4ZVXgg

It might be worth giving Aaron at Letusdirect a call for instructions.

Last edited by Bob Hart; August 9th, 2008 at 12:32 AM. Reason: added URL
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Old August 9th, 2008, 03:42 PM   #3
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My Youtube clip in this case is now quite old and should be regarded as a very inaccurate example of the general operating principle of these adaptors.

http://www.youtube.com/watch?v=yugfv4ZVXgg
Jeepers that thing has got a massive motor.

I went one step crazier than anyone else has probably gone: I took my Letus Extreme apart and stripped all parts of that black paint.
I don't know if it was the culprit for the regular black specks I was getting both inside the flip unit and the GG area, but it was driving me insane cleaning the damn thing.
I haven't had a problem with it since, so I suspect I might have fixed the problem.
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Old August 9th, 2008, 10:19 PM   #4
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QUOTE:

"Jeepers that thing has got a massive motor."

Letus on roids. - It is a smaller tracker motor from a CD player. There are two styles, a larger can motor which drives a reduction gear set and is identical to the CD hub drive motor and this smaller style motor which drives a screwjack and is similar to the older screwjack actuators found in floppy disk drives.

I was after a larger groundglass excursion in the ballpark of 2mm to eliminate the "film-of-grain" issue people were then complaining about with the coarser pre-"Extreme" groundglass texture. I got about 1.5mm from it.

I'm not too sure about stripping the black paint. Untreated aluminium and moisture may give you a white powder problem in the future and sourced from the same places your black paint problem would have come from, the joints between assemblies.

If you are getting flakes coming off from disturbing the joints during maintenance, you may find wiping a very thin almost dry smear of canola oil along the joint will immobilise any paint flakes which crush loose on re-assembly. The canola will eventually set and then not wick out into other areas. The downside is that once jelled or set firm, it may pull paint off if you dismantle the Letus in future.

A matte black internal finish is also desirable for eliminating any stray light which might otherwise be reflecting around inside which may reduce contrast in your image or even show as broad fixed pattern areas.

Last edited by Bob Hart; August 9th, 2008 at 10:26 PM. Reason: added text
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Old August 9th, 2008, 10:27 PM   #5
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Thanks Bob, Managed to clean it. Looks fine now. Cheers mate.
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Old August 9th, 2008, 10:30 PM   #6
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What is it they say over your way - "You're welcome, we aims to please."
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Old August 10th, 2008, 06:25 AM   #7
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Quote:
Originally Posted by Bob Hart View Post
QUOTE:

I'm not too sure about stripping the black paint. Untreated aluminium and moisture may give you a white powder problem in the future and sourced from the same places your black paint problem would have come from, the joints between assemblies. .
There was no paint on the inside... it was just anodized black (like the outside is now).

Quote:
If you are getting flakes coming off from disturbing the joints during maintenance, you may find wiping a very thin almost dry smear of canola oil along the joint will immobilise any paint flakes which crush loose on re-assembly. The canola will eventually set and then not wick out into other areas. The downside is that once jelled or set firm, it may pull paint off if you dismantle the Letus in future. .
I re-smeared expensive marine axel grease on the inside for dust trap purposes. Hopefully that will not harden. Actually, hopefully I'll never have to take the damn thing apart again! :)
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Old August 10th, 2008, 07:14 AM   #8
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Aww Man.


I hope you have not coated the entire inner surface areas of the casework with marine grease, if so, not more than a very thin dry smear.

Marine grease may not have tolerance for high temperatures. Light fractions may come off to condense upon and fog your optics if the adaptor gets warm.

The same vapours may also eventually perish the rubber components on the groundglass panel and the prism retention wedges but probably not before the device is retired for other reasons.

Oils may also separate out and creep.
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Old August 10th, 2008, 02:00 PM   #9
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Aww Man.


I hope you have not coated the entire inner surface areas of the casework with marine grease, if so, not more than a very thin dry smear.

Marine grease may not have tolerance for high temperatures. Light fractions may come off to condense upon and fog your optics if the adaptor gets warm.

The same vapours may also eventually perish the rubber components on the groundglass panel and the prism retention wedges but probably not before the device is retired for other reasons.

Oils may also separate out and creep.

I just smeared a very thin coating, and only inside the section with the prism. The area with the groundglass I'm not concerned about having to take apart an clean, so no grease... it's the bits of black paint that were on the prism that were driving me insane, as not all surfaces are exposed to wiping if the compressed air wouldn't budge the little buggars.
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Old August 10th, 2008, 07:29 PM   #10
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If that is the case you may get away with it as long as there is clearance betwen the flat surfaces of the prism and the casework. If you get a fogging effect or patches in your image, that is where it will be coming from.

As for "compressed air wouldn't budge the little buggars" I found putting the device near an operating CRT television set while you blast it helps keep the dust moving out but my method was recently put down like the mad dog it is when a dvinfo visitor tried it over your way in damp conditions where static electricity does not build like in dry climates.

I have a home made adaptor which is built up from PVC sewer pipe, That stuff and the sawdust which comes off it is a natural for static attraction. I can clean and clean forever and a piece still comes from somewhere as soon as the glass disk spins.

Mostly it sticks to the glass disk but sooner or later flies off between the two prisms just where it cannot be got at.
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Old August 10th, 2008, 08:35 PM   #11
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As for "compressed air wouldn't budge the little buggars" I found putting the device near an operating CRT television set while you blast it helps keep the dust moving out but my method was recently put down like the mad dog it is when a dvinfo visitor tried it over your way in damp conditions where static electricity does not build like in dry climates..
Wow, great idea! I'm sure it would work here in NZ as I've spent many a time cleaning a coating of dust that has been attracted to the CRT tube.


Quote:
Mostly it sticks to the glass disk but sooner or later flies off between the two prisms just where it cannot be got at.
Yeah, that's the part that is a mission for me to clean!
I can deal with pulling off the GG cover. Any bits that won't budge with compressed air are accessible with a lens brush thankfully... but in that prism area Aaaaargh! - and it always sticks out like dog's balls on video because it's the black paint chips.
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Old August 10th, 2008, 11:10 PM   #12
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Some notes on cleaning on Letus website:
http://support.letusdirect.com/index...gory=C1&act=32

Cheers.
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