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Richard123vmt
Tinkerer
Username: Richard123vmt
Post Number: 1
Registered: 01-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 19, 2008 - 11:28 pm: | 
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I wonder if anyone can help me out with a DSB lens problem.
I came across this post:
Posted on Monday, February 27, 2006 - 06:54 pm:
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"If the blades are stuck (as the post indicates) the lens will need to be disassembled from the rear.
There are four cross point screws which need to be removed. They are sometimes a bit difficult and may need same acetone for loosening. Once removed, the back assembly exposes the rear lens group which is held in place with a screw mounted retainer. Once this is removed, the rear lens group may be removed, remembering that the rearmost lens is now loose and the plastic container which holds the group is a friction fit which needs to be removed carefully. Now to the front.
Unscrew the whole front component (holds the name ring) and then remove the three screws holding the focus ring on. Then remove the front lens group which is a friction fit. At this point you have removed all of the glass and the diaphragm can be carefully flush cleaned with alcohol or naptha. "
I have a DSB 50mm lens which had a stuck, dirty diaphragm. I succeeded in cleaning it by squirting electronics cleaner in ( I know this is not the correct method). It worked so that now the diaphragm is "snappy" as they say. Unfortunately, there is dirt splattered on the adjacent lens surfaces and additional ablutions did not remove this. I found the description above helpful since I did not know for sure that removing the small retainer plates at the rear would release the rear part of the lens. Am I correct in concluding that I would then be able to clean the front surface of the rear lens and also, working through the open diaphragm, the rear surface of the front assembly? This would be all that I needed.
I have removed the front shield, three screws and focus ring, but do not see how this gets me near the diaphragm. Are the lens elements cemented in--and if so are they removed by heating to 275 degrees, as I read? Or am I missing something about how the front comes off the rear?
I have also learned to remove the screw cap over the rearmost element of the rear part of the lens, but the second element is one of the ones which need cleaning and is not removable that I can see. Is the rearmost element (closest to the film) symetrical? I am not sure I have it in right, although it is the least of my problems.
If I can clean both dirty surfaces by removing the rear section, as you described, then my only problem is finding a screwdriver that will work with those screws which are slightly offset against the case.
Are there any diagrams online of this lens or other explanatory materials? Thanks if you can help--(or even if you cannot).
--Richard . |
Mikel
Tinkerer
Username: Mikel
Post Number: 71
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 20, 2008 - 03:29 pm: |
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Richard-
This is a six element symmetrical planar type. Let's take all of the glass out to clean it. There are three elements in front in a completely sealed plastic unit. I hope none of that electronics cleaner you used got inside the sealed front unit. Unscrew and remove the name ring and then unscrew the black retaining ring which holds the front lens unit in place. The front lens unit is a friction fit and may come right out but it might also be very tight and if tight (some are very tight)can be worked out with a rubber jar lid grip pad. Once it's out, let's go to the back.
Remove the four screws holding the lens mount and remove it. Next remove the black ring as you did before and remove the loose lens element. The remaining cemented lens pair are sealed in plastic as a unit and can be worked out of their friction fit, just like the front. If it is very tight, you might try working an exacto blade around the seam. Once it's out, you can flush clean the diaphragm blades in place with naptha (ronsonol) or other solvent if you feel this is necessary. Let it dry overnight and check your blades the next day. Flush and dry again if necessary. If they look good, clean the glass and reassemble the lens. If you really need to disassemble the blades, you do it from the front by removing the three screws inside the lens barrel which hold a retaining plate over the blades. Hopefully you will not have to do that.
Check back with any more questions you might have.
Mike |
Richard123vmt
Tinkerer
Username: Richard123vmt
Post Number: 2
Registered: 01-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 20, 2008 - 07:36 pm: |
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Dear MikeL,
Okay but I can see myself messing up where exacto blades come into play. Wouldn't removing the two retainer plates ( two screws each) inside the rear allow me to pull off the rear section exposing the diaphragm? The diaphragm is already freed up satisfactorily. I want to do as little surgery as possible. I am afraid if I get the glass out at all I will do damage to it of one kind or another. |
Mikel
Tinkerer
Username: Mikel
Post Number: 72
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 21, 2008 - 05:58 pm: |
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Richard-
Getting the rear lens unit out by itself is the best approach. Remove any oil that's on the plastic. Try the rubber jar lid thing. Get a good grip and it will come out. It's always tempting to remove some more screws but it's never a good idea to remove more than you have to. You don't want to remove the screws- unless you really want to do more than you need to.
Mike |
Richard123vmt
Tinkerer
Username: Richard123vmt
Post Number: 3
Registered: 01-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 24, 2008 - 03:56 pm: |
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I see. So we are talking about the second lens forward from the rear? The rearmost one comes off easily. I must confess I am not familiar with the rubber jar lid thingy. What I am thinking of is a mat of rubber used to grip jars. I did try griping it with some scotch tape but no good. However I think you have given me what I need to know and I thank you once again. Probably it will come out easier than it seems with a bit of work with an exacto. And of course, it is not like the lens is so valuable I can't afford to face the loss if it should break. However, I am suddenly out of quiet time for a while, so it will have to wait. |
Richard123vmt
Tinkerer
Username: Richard123vmt
Post Number: 5
Registered: 01-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 24, 2008 - 08:47 pm: |
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Success! On further inspection I discovered what is what. I was under the mistaken impression that I was trying to lossen the actual glass element out of the barrel and that the lip in there was a spacer. So I was trying to pull up the spacer when something budged--but it was the entire barrel. What I needed to do was so much easier and safer than what I was attempting!
So I took out the barrel cleaned the surfaces and the lens is back together and working--so far as viewing through the viewfinder shows. I notice however the fresnel lens does not seem to be getting clear at focus, although the split line is working. Maybe it is the low level of light? I will try it in daytime. |
Richard123vmt
Tinkerer
Username: Richard123vmt
Post Number: 6
Registered: 01-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 25, 2008 - 03:58 pm: |
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Reticulated spot (not 'fresnel lens') was not working becuase I had sky filter on. With filter off, works fine. Problem solved. |
