P3D Viewers lemons?

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Brenda asked if there are viewers that are "lemons" (bad to start)
like some cars.  Viewers are very simple instruments.  They might
suffer from some common or not-so-common problems, but there are
no real lemons out there.

Examples of common problems:

- Kodaslide II: "Frozen" focusing (focusing is stuck in one position,
  very common if the viewer has not been used for a long time), 
  AC cord is "open" (wires are broken) usually at the point of entry
  into the viewer.

- Red button: Lenses have "fog" (cement between the two elements is
  separating), "does not work" (contacts need cleaning).

- TDC Deluxe:  "focusing has problems" (the plastic pinions are worn
  and the metal rack does not engage properly)

- Green button: Problen with lens' alignment as I mentioned.  Also the
  interocular slips back, the focusing is hard to turn.

- Problems with reflectors are common in all viewers.  The green button
  turns off white with time, the KII can be damaged, RB also off-white
  Revere/Wollensak and others the reflector can be damaged causing
  shadows.  Some reflectors can be changed, especially if they are
  of the "flat" type (RB, GB, Kodaslide)

- Problems with dirty switch contacts are also common.  These lead to 
  light-flickering, more pronounced when a bright bulb is used.  Easy
  to correct by cleaning the contacts.

Examples of not-so-common problems:

- Kodaslide II:  Is actually a KI with changed name-plate.  So it has
  single element (plastic) lenses instead of achromats.  Have never
  seen that but can happen and then your KII is a real "lemon"!

- Red button:  Achromats have been installed reversed, front to back.
  I have seen this 3 times.  Leads to terrible distortion of all sorts
  qualifying for a "lemon".  Also, not red button but white button which
  means that it has single element lenses instead of achromats.

Viewers are simple but they need some periodical maintenance to keep
working well.

-- George Themelis


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