B&L SZ4 Does not stay in Focus when Zoomed

[dazz]

Hi
When I zoom my B&L SZ4, it doesn't stay in focus.
Is this normal?
Is there an adjustment?

[Scarodactyl]

Yeah, you need to set it up for your eyes.
Put a flat, detailed subject under the scope. A phone screen or peinted page will do. Start by zooming all the way in. Focus with the focus knobs. Then zoom out and adjust the oculars until the image is back in focus. Repeat if needed.

[lorez2]

If what Scarodactyl suggests does not solve the problem, it may be that the objective cells are no longer properly positioned on the slide bars. There were fixtures and jigs available that would facilitate the process, but that was long, long ago.

lorez2

[BramHuntingNematodes]

Sometimes this.problem can be helped by adjusting the eyepiece distance

[dazz]

Hi
I thought it should stay in focus on zoom. It is not a show stopper. I don't adjust zoom too often.
I only have one adjustable ocular, and I have already adjusted that for my eyesight.

Does anyone have a picture of the jigs?

[BramHuntingNematodes]

It should be parfocal throughout the zoom. Does it stay in focus when zooming out?

[dazz]

Hi
No. If I zoom, I have to refocus. It doesn't matter whether I focus in or out.

[lorez2]

The objective cells are no longer properly positioned on the slide bars. Until this is done, no other adjustments are going to have any effect.

lorez

[dazz]

Hi
Is there any guidance on correctly positioning the objectives cells on the slide bars?

[BramHuntingNematodes]

https://www.covingtoninnovations.com/stereozoom/

Here's the adjustments you should make sure you have done before taking it apart and then instructions on taking.it apart.

[lorez2]

The links offered some good information, but did not get to the parfocal operations (at least those I saw). I stored all my equipment many years ago and have not worked on a B&L since... I will dig into the archives to see what I can uncover. There are a few special fixtures, centering eyepieces and targets and a variety of tools. I imagine that a creative person could probably create a kit that would be effective. As I remember, it is an hour, or so, job if there are no other complications. One of the things I saw most frequently were damaged eyepiece mounts. They would get "dinged" and only the slightest damage would render them junk.

lorez

[BramHuntingNematodes]

I've only adjusted the lenses in the sz7, where my advice there would be, "don't". Someone out there has a sz4 service manual pdf pretty sure. I only have the sz7 one.

[dazz]

Hi
The instructions on adjustment included a procedure to fix my exact problem. That is to rotate the right eye piece that is held in place with a set screw. In my case the set screw is missing.
I need a replacement screw but there is absolutely no danger of finding spare parts here.
If I can't find a screw, I will drill it out and tap it for a metric screw.


Does anyone know the specs for the B&L thread?

[BramHuntingNematodes]

Not exactly sure but B&L stuck with imperial units until the very end.