Have you tried rotating the condensers (I would guess there's a way, but I'm
not familiar with the enlarger).  If the spots move when you rotate the
condensers, then you're probably right.  Move one at a time, turning it 90
degrees and see if the spots move 90 degrees as well.  If not, then it's got
to be something else like the enlarging lens or glass in a glass carrier.  A
wild guess, but it could also be a hole in the camera shutter curtain.  You
didn't mention what format you're using, but you can analyze this
possibility further.

I have a bubble in the condenser in my Beseler.  It creates a bit of uneven
light in certain formats, but never a full white spot.  A quick way to check
is tape a piece if drafting paper to the bottom condenser and see if the
trouble disappears.  This will make a diffuser out of the condenser (to some
degree) and will help in locating the problem.

I don't think bubbles inside the glass will be created other than during the
making of the condenser lens, so if you didn't have problems before and now
you do, there must be some other reason(s).  As suggested already, rotating
the lenses 90 degrees is a good way to tell if the problem is in the
condensers or somewhere else.

I think that a bubble inside does not diffract light, it will refract it,
tho.

You already answered your question within your post: look for chips, bubbles
and scratches.  I'd also ask for 2 days money back if not satisfied, or if
the guy has a similar enlarger, ask him to let them try the condensers in
his enlarger.  BTW, small chips at the very edge of the glass will not
affect the evenness of light.

Is it an enlarger bulb? or is it a regular frosted bulb?  if the latter,
look if it has lettering at the bottom, if it does that maybe your problem,
besides you should use a enlarger bulb not a regular bulb, even if it
doesn't have letters on it.

Guillermo

I had the same problem with a cheapo condenser 6 x 6 enlarger that I
was using during a year in Japan. Went down to the hardware store and
got a piece of translucent plastic and cut it to fit the condenser
housing, placing it at the very bottom of the stack, so it was closest
to the negative. The improvement was dramatic, sort of like having a
cold light, only not cold. The change was much like having a cold
light: contrast was a bit softer, and dust on the condensers and
negative was much less of a factor.

   Its quite possible for flaws in the condensers to show
up on prints but you should be able to see them on the
baseboard. Try focusing a negative on white paper and
removing the negative. Since you know where to expect the
spots examine the open gate image on the baseboard to see
what is causing it. Stop down the lens since this will tend
to focus and exagerate the spots. Sometimes moving the lens
toward the condensers will focus their surfaces making any
blemishes very obvious.
   The glass used for condensers, at least in Omega
enlargers, seems to be quite brittle. It will develop small
chips on the suface if the two condensers are allowed to
come in contact during cleaning.
  I would try cleaning the condensers with dishwashing
detergent and warm water. That should get nearly anything
off. If not try any of the "streak free" cleaners on the
market. 99% Isopropyl alcohol will take off oil, grease,
etc, that the soap may not remove. There isn't much that can
be done about scratches and gouges. Chips at the edge should
have little or no effect.
  Small defects can sometimes be hidden by reversing the
postion of the condensers.
  The lamp should be a special enlarging lamp. These have a
coating of very diffusing material and are much more diffuse
than a reading lamp. Also, the makers name is on the neck,
not of the end of the bulb. The correct lamp is a No.
PH-211, these are still made and should be available through
photo supply houses like Calumet or Freestyle.

  If it turns out to be the condensers you can get
replacements from three sources:
Harry Taylor
Classic Enlargers
145 Jeanne Ct.
Stamford, CT  06903

203 329 9228

http://www.classic-enlargers.com

Another source is Bob Watson. Bob does not have a web site,
you can reach him at:rwatson767@aol.com

  I believe that new condensers are available from
Omega-Satter, but they are probably quite expensive.
www.omegasatter.com/

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com