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Drifting South West

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  • david barriball
    Hello, I have a problem with the subject drifting diagonally, when fine focusing up and down. Maybe the condenser is not centered correctly, or something else
    Message 1 of 11 , May 1, 2010
      Hello,
      I have a problem with the subject drifting diagonally, when fine focusing
      up and down.
      Maybe the condenser is not centered correctly, or something
      else is out of line!
      Someone might suggest something.
      Thanks,
      David

      [Non-text portions of this message have been removed]
    • mervhob
      Hi David, It is most likely to be misalignment in the illuminating train, and to establish the cause look carefully at the image as you operate the fine focus.
      Message 2 of 11 , May 1, 2010
        Hi David,

        It is most likely to be misalignment in the illuminating train, and to establish the cause look carefully at the image as you operate the fine focus. If the centre of the image stays in the same place, and only the out of focus components move diagonally, the problem is probably in the condenser centring, or lamp centring. Or tilt in the condenser axis - see my previous post in reply to Rolf and his problems with condenser centring. If the whole image, centre and out of focus components move diagonally, the problem is mechanical, and can be down to slop in the fine focus slide. I take it that the coarse focus is okay, and only the fine focus gives the problem. Can you tell me what kind of microscope we are talking about - is it limb focused or stage focused, and what is the make? If it is stage focused it can also be the stage not being at right angles to the optical axis.The first thing is to establish whether the cause is optical or, mechanical - if it is optical it should be easy to fix, and if mechanical, some judicious shimming may do the trick!

        Cheers,

        Merv






        --- In Microscope@yahoogroups.com, "david barriball" <focusball3@...> wrote:
        >
        > Hello,
        > I have a problem with the subject drifting diagonally, when fine focusing
        > up and down.
        > Maybe the condenser is not centered correctly, or something
        > else is out of line!
        > Someone might suggest something.
        > Thanks,
        > David
        >
        > [Non-text portions of this message have been removed]
        >
      • david barriball
        It is a Lomo, it is limb focused, when get the microscope out, will see if corase focus does it, also. Can not stop, visitors, it was seen most with x80.
        Message 3 of 11 , May 1, 2010
          It is a Lomo, it is limb focused, when get the microscope out,
          will see if corase focus does it, also.
          Can not stop, visitors, it was seen most with x80.
          Thanks,
          David
          ----- Original Message -----
          From: mervhob
          To: Microscope@yahoogroups.com
          Sent: Saturday, May 01, 2010 12:36 PM
          Subject: [Microscope] Re: Drifting South West





          Hi David,

          It is most likely to be misalignment in the illuminating train, and to establish the cause look carefully at the image as you operate the fine focus. If the centre of the image stays in the same place, and only the out of focus components move diagonally, the problem is probably in the condenser centring, or lamp centring. Or tilt in the condenser axis - see my previous post in reply to Rolf and his problems with condenser centring. If the whole image, centre and out of focus components move diagonally, the problem is mechanical, and can be down to slop in the fine focus slide. I take it that the coarse focus is okay, and only the fine focus gives the problem. Can you tell me what kind of microscope we are talking about - is it limb focused or stage focused, and what is the make? If it is stage focused it can also be the stage not being at right angles to the optical axis.The first thing is to establish whether the cause is optical or, mechanical - if it is optical it should be easy to fix, and if mechanical, some judicious shimming may do the trick!

          Cheers,

          Merv






          ------------------------------------------------------------------------------



          No virus found in this incoming message.
          Checked by AVG - www.avg.com
          Version: 9.0.814 / Virus Database: 271.1.1/2847 - Release Date: 05/01/10 07:27:00


          [Non-text portions of this message have been removed]
        • mervhob
          David, Fine focus on the LOMO is on the stage, coarse focus on the limb, so I am guessing that the problem is possibly condenser centring. Which model
          Message 4 of 11 , May 1, 2010
            David,

            Fine focus on the LOMO is on the stage, coarse focus on the limb, so I am guessing that the problem is possibly condenser centring. Which model condenser is it - the Abbe or the Aplanatic? There are no auxilary active centring screws on the LOMO. The first test is to remove an eyepiece, close the aperture iris and check that the image of the aperture iris is in the middle of the field of view in the back focal plane of the objective. If it is not - use the centring screws on the condenser mounting bracket to ensure it is central. Then check that the lamp filament image is central in the back focal plane. If you have the Aplanatic condenser with the capability of oblique illumination by shifting the aperture iris on a slide, check that that is locked into the central position before attempting any other adjustments.

            Cheers,

            Merv

            --- In Microscope@yahoogroups.com, "david barriball" <focusball3@...> wrote:
            >
            > It is a Lomo, it is limb focused, when get the microscope out,
            > will see if corase focus does it, also.
            > Can not stop, visitors, it was seen most with x80.
            > Thanks,
            > David
            > ----- Original Message -----
            > From: mervhob
            > To: Microscope@yahoogroups.com
            > Sent: Saturday, May 01, 2010 12:36 PM
            > Subject: [Microscope] Re: Drifting South West
            >
            >
            >
            >
            >
            > Hi David,
            >
            > It is most likely to be misalignment in the illuminating train, and to establish the cause look carefully at the image as you operate the fine focus. If the centre of the image stays in the same place, and only the out of focus components move diagonally, the problem is probably in the condenser centring, or lamp centring. Or tilt in the condenser axis - see my previous post in reply to Rolf and his problems with condenser centring. If the whole image, centre and out of focus components move diagonally, the problem is mechanical, and can be down to slop in the fine focus slide. I take it that the coarse focus is okay, and only the fine focus gives the problem. Can you tell me what kind of microscope we are talking about - is it limb focused or stage focused, and what is the make? If it is stage focused it can also be the stage not being at right angles to the optical axis.The first thing is to establish whether the cause is optical or, mechanical - if it is optical it should be easy to fix, and if mechanical, some judicious shimming may do the trick!
            >
            > Cheers,
            >
            > Merv
            >
            >
            >
            >
            >
            >
            > ------------------------------------------------------------------------------
            >
            >
            >
            > No virus found in this incoming message.
            > Checked by AVG - www.avg.com
            > Version: 9.0.814 / Virus Database: 271.1.1/2847 - Release Date: 05/01/10 07:27:00
            >
            >
            > [Non-text portions of this message have been removed]
            >
          • david barriball
            Merv, The microscope says made in USSR, the condenser aperture 1.2. can t find which condenser it is, from a polarizing microscope. Have moved the bulb in it s
            Message 5 of 11 , May 1, 2010
              Merv,
              The microscope says made in USSR, the condenser aperture 1.2.
              can't find which condenser it is, from a polarizing microscope.
              Have moved the bulb in it's housing, this has improved it a lot.
              It was most noticed with the x80w objective, no eye piece,
              attached to a camera.
              This is a fresh bulb, the last one ended it's life.
              Thanks for your help,
              David



              ----- Original Message -----
              From: mervhob
              To: Microscope@yahoogroups.com
              Sent: Saturday, May 01, 2010 11:57 PM
              Subject: [Microscope] Re: Drifting South West





              David,

              Fine focus on the LOMO is on the stage, coarse focus on the limb, so I am guessing that the problem is possibly condenser centring. Which model condenser is it - the Abbe or the Aplanatic? There are no auxilary active centring screws on the LOMO. The first test is to remove an eyepiece, close the aperture iris and check that the image of the aperture iris is in the middle of the field of view in the back focal plane of the objective. If it is not - use the centring screws on the condenser mounting bracket to ensure it is central. Then check that the lamp filament image is central in the back focal plane. If you have the Aplanatic condenser with the capability of oblique illumination by shifting the aperture iris on a slide, check that that is locked into the central position before attempting any other adjustments.

              Cheers,

              Merv




              [Non-text portions of this message have been removed]
            • John
              Hi David If you examine the output from the eyepiece when the scope is in focus with a 10x eyeglass or loupe etc you should be able to check that the condenser
              Message 6 of 11 , May 2, 2010
                Hi David
                If you examine the output from the eyepiece when the scope is in focus with a 10x eyeglass or loupe etc you should be able to check that the condenser iris and the bulb are centred. This will also allow you to correctly focus the condenser so that the image of it's iris is sharp. The image of the bulb filament should also be sharp if there are no diffusers in it's light path. They may give you a fuzzy image or just a patch of light. In the latter case the best thing to do is focus it for max light. That will be a combination of centring it and focusing it.

                Lacking a loupe the same thing can be done with a pin hole eyepiece but not so easily. That's just some old eyepiece optics removed and perforated opaque disc fitted at the eye end some how.

                John

                --- In Microscope@yahoogroups.com, "david barriball" <focusball3@...> wrote:
                >
                > Merv,
                > The microscope says made in USSR, the condenser aperture 1.2.
                > can't find which condenser it is, from a polarizing microscope.
                > Have moved the bulb in it's housing, this has improved it a lot.
                > It was most noticed with the x80w objective, no eye piece,
                > attached to a camera.
                > This is a fresh bulb, the last one ended it's life.
                > Thanks for your help,
                > David
                >
                >
                >
                > ----- Original Message -----
                > From: mervhob
                > To: Microscope@yahoogroups.com
                > Sent: Saturday, May 01, 2010 11:57 PM
                > Subject: [Microscope] Re: Drifting South West
                >
                >
                >
                >
                >
                > David,
                >
                > Fine focus on the LOMO is on the stage, coarse focus on the limb, so I am guessing that the problem is possibly condenser centring. Which model condenser is it - the Abbe or the Aplanatic? There are no auxilary active centring screws on the LOMO. The first test is to remove an eyepiece, close the aperture iris and check that the image of the aperture iris is in the middle of the field of view in the back focal plane of the objective. If it is not - use the centring screws on the condenser mounting bracket to ensure it is central. Then check that the lamp filament image is central in the back focal plane. If you have the Aplanatic condenser with the capability of oblique illumination by shifting the aperture iris on a slide, check that that is locked into the central position before attempting any other adjustments.
                >
                > Cheers,
                >
                > Merv
                >
                >
                >
                >
                > [Non-text portions of this message have been removed]
                >
              • david barriball
                John, you did not say what size of objective x20 or 40. Thanks, David ... From: John To: Microscope@yahoogroups.com Sent: Sunday, May 02, 2010 10:26 AM
                Message 7 of 11 , May 2, 2010
                  John, you did not say what size of objective x20 or 40.
                  Thanks,
                  David
                  ----- Original Message -----
                  From: John
                  To: Microscope@yahoogroups.com
                  Sent: Sunday, May 02, 2010 10:26 AM
                  Subject: [Microscope] Re: Drifting South West



                  Hi David
                  If you examine the output from the eyepiece when the scope is in focus with a 10x eyeglass or loupe etc you should be able to check that the condenser iris and the bulb are centred. This will also allow you to correctly focus the condenser so that the image of it's iris is sharp. The image of the bulb filament should also be sharp if there are no diffusers in it's light path. They may give you a fuzzy image or just a patch of light. In the latter case the best thing to do is focus it for max light. That will be a combination of centring it and focusing it.

                  Lacking a loupe the same thing can be done with a pin hole eyepiece but not so easily. That's just some old eyepiece optics removed and perforated opaque disc fitted at the eye end some how.

                  John

                  --- In Microscope@yahoogroups.com, "david barriball" <focusball3@...> wrote:
                  >
                  > Merv,
                  > The microscope says made in USSR, the condenser aperture 1.2.
                  > can't find which condenser it is, from a polarizing microscope.
                  > Have moved the bulb in it's housing, this has improved it a lot.
                  > It was most noticed with the x80w objective, no eye piece,
                  > attached to a camera.
                  > This is a fresh bulb, the last one ended it's life.
                  > Thanks for your help,
                  > David
                  >
                  >
                  >
                  > ----- Original Message -----
                  > From: mervhob
                  > To: Microscope@yahoogroups.com
                  > Sent: Saturday, May 01, 2010 11:57 PM
                  > Subject: [Microscope] Re: Drifting South West
                  >
                  >
                  >
                  >
                  >
                  > David,
                  >
                  > Fine focus on the LOMO is on the stage, coarse focus on the limb, so I am guessing that the problem is possibly condenser centring. Which model condenser is it - the Abbe or the Aplanatic? There are no auxilary active centring screws on the LOMO. The first test is to remove an eyepiece, close the aperture iris and check that the image of the aperture iris is in the middle of the field of view in the back focal plane of the objective. If it is not - use the centring screws on the condenser mounting bracket to ensure it is central. Then check that the lamp filament image is central in the back focal plane. If you have the Aplanatic condenser with the capability of oblique illumination by shifting the aperture iris on a slide, check that that is locked into the central position before attempting any other adjustments.
                  >
                  > Cheers,
                  >
                  > Merv
                  >
                  >
                  >
                  >
                  > [Non-text portions of this message have been removed]
                  >






                  ------------------------------------------------------------------------------



                  No virus found in this incoming message.
                  Checked by AVG - www.avg.com
                  Version: 9.0.814 / Virus Database: 271.1.1/2847 - Release Date: 05/01/10 07:27:00


                  [Non-text portions of this message have been removed]
                • John
                  On one scope I found that the 40x was best but not sure if I had the eyeglass in the right place on the others. Shortly after trying it following a suggestion
                  Message 8 of 11 , May 2, 2010
                    On one scope I found that the 40x was best but not sure if I had the eyeglass in the right place on the others. Shortly after trying it following a suggestion on here I changed to a scope with a bertrand lens. I would try them all but remember that the condenser iris wont be seen unless the condenser is focused and it best to shut it down well below the na of the objective so that it can be clearly seen. Focusing the condenser is the 1st step then the lamp can be focused to that. As you move the eyeglass around you should be able to focus on the rear element of the objective in use. Then raise/lower the condenser until the iris comes into focus.

                    It's worth adding that if the scope lacks some mechanism for centring the condenser I've yet to see a perfectly centred iris. In practice it doesn't seem to matter that much but may mean that the iris needs to be shut down a little more for best contrast and it's like using very slight oblique illumination that will only be apparent when photographing certain specimens. Many modern scopes centre the field iris with the condenser. It's interesting to think about what's going on when everything is centred that way. There will still be errors in the objectives and turret etc.

                    John

                    --- In Microscope@yahoogroups.com, "david barriball" <focusball3@...> wrote:
                    >
                    > John, you did not say what size of objective x20 or 40.
                    > Thanks,
                    > David
                    > ----- Original Message -----
                    > From: John
                    > To: Microscope@yahoogroups.com
                    > Sent: Sunday, May 02, 2010 10:26 AM
                    > Subject: [Microscope] Re: Drifting South West
                    >
                    >
                    >
                    > Hi David
                    > If you examine the output from the eyepiece when the scope is in focus with a 10x eyeglass or loupe etc you should be able to check that the condenser iris and the bulb are centred. This will also allow you to correctly focus the condenser so that the image of it's iris is sharp. The image of the bulb filament should also be sharp if there are no diffusers in it's light path. They may give you a fuzzy image or just a patch of light. In the latter case the best thing to do is focus it for max light. That will be a combination of centring it and focusing it.
                    >
                    > Lacking a loupe the same thing can be done with a pin hole eyepiece but not so easily. That's just some old eyepiece optics removed and perforated opaque disc fitted at the eye end some how.
                    >
                    > John
                    >
                    > --- In Microscope@yahoogroups.com, "david barriball" <focusball3@> wrote:
                    > >
                    > > Merv,
                    > > The microscope says made in USSR, the condenser aperture 1.2.
                    > > can't find which condenser it is, from a polarizing microscope.
                    > > Have moved the bulb in it's housing, this has improved it a lot.
                    > > It was most noticed with the x80w objective, no eye piece,
                    > > attached to a camera.
                    > > This is a fresh bulb, the last one ended it's life.
                    > > Thanks for your help,
                    > > David
                    > >
                    > >
                    > >
                    > > ----- Original Message -----
                    > > From: mervhob
                    > > To: Microscope@yahoogroups.com
                    > > Sent: Saturday, May 01, 2010 11:57 PM
                    > > Subject: [Microscope] Re: Drifting South West
                    > >
                    > >
                    > >
                    > >
                    > >
                    > > David,
                    > >
                    > > Fine focus on the LOMO is on the stage, coarse focus on the limb, so I am guessing that the problem is possibly condenser centring. Which model condenser is it - the Abbe or the Aplanatic? There are no auxilary active centring screws on the LOMO. The first test is to remove an eyepiece, close the aperture iris and check that the image of the aperture iris is in the middle of the field of view in the back focal plane of the objective. If it is not - use the centring screws on the condenser mounting bracket to ensure it is central. Then check that the lamp filament image is central in the back focal plane. If you have the Aplanatic condenser with the capability of oblique illumination by shifting the aperture iris on a slide, check that that is locked into the central position before attempting any other adjustments.
                    > >
                    > > Cheers,
                    > >
                    > > Merv
                    > >
                    > >
                    > >
                    > >
                    > > [Non-text portions of this message have been removed]
                    > >
                    >
                    >
                    >
                    >
                    >
                    >
                    > ------------------------------------------------------------------------------
                    >
                    >
                    >
                    > No virus found in this incoming message.
                    > Checked by AVG - www.avg.com
                    > Version: 9.0.814 / Virus Database: 271.1.1/2847 - Release Date: 05/01/10 07:27:00
                    >
                    >
                    > [Non-text portions of this message have been removed]
                    >
                  • mervhob
                    Hi David, Badly centred filaments are a common problem with the Russian made bulbs. The condenser is almost certainly the ordinary Abbe. The LOMO condenser
                    Message 9 of 11 , May 2, 2010
                      Hi David,

                      Badly centred filaments are a common problem with the Russian made bulbs. The condenser is almost certainly the ordinary Abbe. The LOMO condenser support ring is in two parts - a sleeve which carries the condenser, supported between the centring screws, and which has a fine thread cut on the top end, and a large crenellated locking nut which locks the whole assmbly to the condenser bracket and slide. Before the centring screws can be adjusted, this locking nut must be loosened. It is easier to remove the whole condenser slide from the microscope, after removing the mirror and the condenser, in order to loosen the nut. If you don't have a suitable pin spanner, fit two drill shanks of suitable size between the jaws of a vice, with the spacing set to fit comfortably between two diametrically opposite crenellations, and protruding from the jaws not more than 1/4".Lower the condenser bracket onto the drill shanks, firmly engaging the crenellataions and rotate anti-clockwise. It should loosen fairly easily, but if it does show signs of corrosion and feels very tight, don't try and force it - apply a little parafin (kerosene) or plus-gas to the threads, let it soak in and try again (Remember, the disaster devils are always lurking in the background....!)
                      Clean up and reassemble, leaving the crenellated lock nut only finger tight, and refit to the microscope. Centre up the aperture iris looking into the back focal after having set up the condenser to the correct height with a low power objective on a suitable slide. Change to the the highest power, refocus on the slide, then observe the back focal plane and the condenser aperture iris. It probably won't be central, and at this point, using a watchmakers screwdriver, centre up the iris, using the three set screws, and check that as it opens and closes, it remains central to the illuminated field in the back focal plane. Gently lock the crenellated nut, and if you try the other objectives in turn, the lower powers should all be substantially central.
                      There is one other peculiarity of LOMO, copied from Zeiss, which is not true of the excellent polarising microscope from that company.
                      The objective turret is carried on a dovetail slide, which is centred by a screw at the top front of the turret. Quite often these are maladjusted, de-centring the turret, and in the case of wear, tilting the whole assembly, misaligning the whole optical axis. While this allows the whole turret assembly to be drawn forward and removed, it is a very weak part of the design - the original Zeiss assembly was brass slides on cast iron - the LOMO version is on soft aluminium, and with continual rotation of the turret, it can cause problems.

                      Cheers,

                      Merv

                      --- In Microscope@yahoogroups.com, "david barriball" <focusball3@...> wrote:
                      >
                      > Merv,
                      > The microscope says made in USSR, the condenser aperture 1.2.
                      > can't find which condenser it is, from a polarizing microscope.
                      > Have moved the bulb in it's housing, this has improved it a lot.
                      > It was most noticed with the x80w objective, no eye piece,
                      > attached to a camera.
                      > This is a fresh bulb, the last one ended it's life.
                      > Thanks for your help,
                      > David
                      >
                      >
                      >
                      > ----- Original Message -----
                      > From: mervhob
                      > To: Microscope@yahoogroups.com
                      > Sent: Saturday, May 01, 2010 11:57 PM
                      > Subject: [Microscope] Re: Drifting South West
                      >
                      >
                      >
                      >
                      >
                      > David,
                      >
                      > Fine focus on the LOMO is on the stage, coarse focus on the limb, so I am guessing that the problem is possibly condenser centring. Which model condenser is it - the Abbe or the Aplanatic? There are no auxilary active centring screws on the LOMO. The first test is to remove an eyepiece, close the aperture iris and check that the image of the aperture iris is in the middle of the field of view in the back focal plane of the objective. If it is not - use the centring screws on the condenser mounting bracket to ensure it is central. Then check that the lamp filament image is central in the back focal plane. If you have the Aplanatic condenser with the capability of oblique illumination by shifting the aperture iris on a slide, check that that is locked into the central position before attempting any other adjustments.
                      >
                      > Cheers,
                      >
                      > Merv
                      >
                      >
                      >
                      >
                      > [Non-text portions of this message have been removed]
                      >
                    • david barriball
                      Thank you Merv and John, I think the bulb is a lot of the problem, but not all of it, operator error also. If the turret is worn, when it is moved it should
                      Message 10 of 11 , May 2, 2010
                        Thank you Merv and John,
                        I think the bulb is a lot of the problem, but not all of it,
                        operator error also.
                        If the turret is worn, when it is moved it should wobble, but
                        don't think that it is worn.
                        David
                        ----- Original Message -----
                        From: mervhob
                        To: Microscope@yahoogroups.com
                        Sent: Sunday, May 02, 2010 1:23 PM
                        Subject: [Microscope] Re: Drifting South West



                        Hi David,

                        Badly centred filaments are a common problem with the Russian made bulbs. The condenser is almost certainly the ordinary Abbe. The LOMO condenser support ring is in two parts - a sleeve which carries the condenser, supported between the centring screws, and which has a fine thread cut on the top end, and a large crenellated locking nut which locks the whole assmbly to the condenser bracket and slide. Before the centring screws can be adjusted, this locking nut must be loosened. It is easier to remove the whole condenser slide from the microscope, after removing the mirror and the condenser, in order to loosen the nut. If you don't have a suitable pin spanner, fit two drill shanks of suitable size between the jaws of a vice, with the spacing set to fit comfortably between two diametrically opposite crenellations, and protruding from the jaws not more than 1/4".Lower the condenser bracket onto the drill shanks, firmly engaging the crenellataions and rotate anti-clockwise. It should loosen fairly easily, but if it does show signs of corrosion and feels very tight, don't try and force it - apply a little parafin (kerosene) or plus-gas to the threads, let it soak in and try again (Remember, the disaster devils are always lurking in the background....!)
                        Clean up and reassemble, leaving the crenellated lock nut only finger tight, and refit to the microscope. Centre up the aperture iris looking into the back focal after having set up the condenser to the correct height with a low power objective on a suitable slide. Change to the the highest power, refocus on the slide, then observe the back focal plane and the condenser aperture iris. It probably won't be central, and at this point, using a watchmakers screwdriver, centre up the iris, using the three set screws, and check that as it opens and closes, it remains central to the illuminated field in the back focal plane. Gently lock the crenellated nut, and if you try the other objectives in turn, the lower powers should all be substantially central.
                        There is one other peculiarity of LOMO, copied from Zeiss, which is not true of the excellent polarising microscope from that company.
                        The objective turret is carried on a dovetail slide, which is centred by a screw at the top front of the turret. Quite often these are maladjusted, de-centring the turret, and in the case of wear, tilting the whole assembly, misaligning the whole optical axis. While this allows the whole turret assembly to be drawn forward and removed, it is a very weak part of the design - the original Zeiss assembly was brass slides on cast iron - the LOMO version is on soft aluminium, and with continual rotation of the turret, it can cause problems.

                        Cheers,



                        [Non-text portions of this message have been removed]
                      • pennine56
                        ... Hello David If your bulb is one of the original Russian designs with coiled filament and poor glass envelope you may wish to consider a bulb like the
                        Message 11 of 11 , May 2, 2010
                          --- In Microscope@yahoogroups.com, "david barriball" <focusball3@...> wrote:
                          >
                          > Thank you Merv and John,
                          > I think the bulb is a lot of the problem, but not all of it,
                          > operator error also.
                          > If the turret is worn, when it is moved it should wobble, but
                          > don't think that it is worn.
                          > David

                          Hello David

                          If your bulb is one of the original Russian designs with coiled filament and poor glass envelope you may wish to consider a bulb like the Philips 13347W with same Ba15d base which is widely available. It better centred, has a flat filament and flattened higher quality glass envelope, the difference in quality of the projected filament in my Russian lamp onto a wall for my LOMO Biolam is quite striking. It is a 6V 15W rather than 9V so have to be careful not to overrun with a 9V PSU.

                          Images of bulb and projected images of Russian and Philips compared at

                          http://www.microscopy-uk.org.uk/mag/artnov05/dwlomolamps.html#Tips

                          They are about £7-50 to buy but bought a job lot on eBay a while back so have way more than I need. If you're in UK, drop me a line if would like one for say a third of that price.

                          regards
                          David
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