This is a hard one to get information on: I want to know how to test the photo cell (tube) in my Victor Animatophone. The audio is loud, but on the variable density sound track it is distorted. This may also be due to that portion of the film being faded, as this would erase all of the faint bars, causing flats in the audio. Furthermore, my other problem is a loss of high notes. The variable area sound track is good, but the variable density sound track lacks much highs. Actually the highs are pretty bad for all film. Sending audio through the amplifier from a CD works extremely well. As for the exciter, I also have the slit adjusted really thin, so this is not likely to hinder high frequency reproduction.

I need to learn a lot more about photo tubes, though, because there isn't much out there on them.

Thomas

Hi Thomas

With increasing light a photo tube conducts. A weak photo tube should give low volume. As they age glass darkens and output change is reduced. Don't see how you would have distortion?

A photo tube can be tested with a VOM. Set a Simpson 260 or Triplett 630 on the highest resistance scale. Connect the two leads in series with your photo tube. In bright light there will be a reading. Resistance will increase as the tube is made dark. If you don't get a reading reverse leads.

These VOM have a 22 1/2 or 30 volt battery for the highest resistance scale. This voltage is enough to test your photo tube which may operate on 90 volts in the actual circuit.

If you don't have a VOM with high voltage battery use a low current scale on your meter. Test the photo cell with a battery & meter in series.

Photo tubes make neet projects. If you list your tube number I might have specifications?

Norm

:This is a hard one to get information on: I want to know how to test the photo cell (tube) in my Victor Animatophone. The audio is loud, but on the variable density sound track it is distorted. This may also be due to that portion of the film being faded, as this would erase all of the faint bars, causing flats in the audio. Furthermore, my other problem is a loss of high notes. The variable area sound track is good, but the variable density sound track lacks much highs. Actually the highs are pretty bad for all film. Sending audio through the amplifier from a CD works extremely well. As for the exciter, I also have the slit adjusted really thin, so this is not likely to hinder high frequency reproduction.
:
:I need to learn a lot more about photo tubes, though, because there isn't much out there on them.
:
:Thomas

Well, the glass is not dark. On the highest resistance scale on my Simpson 260, which uses 5 cells for the high resistance setting, when I expose the tube to bright light, it reads about 1 meg. It generates a very small voltage when on the 2.5 volt scale. Audio is loud on the projector. The distortion, I think, is actually due to the film fading, which would cause all of the bars on density modulation that were really faint in the first place, to disappear all together, causing flats in the audio. My biggest problem is lack of high frequency response, though this may be partially due to the film, too, which was copied poorly in the first place.

Thomas

:Hi Thomas
:
: With increasing light a photo tube conducts. A weak photo tube should give low volume. As they age glass darkens and output change is reduced. Don't see how you would have distortion?
:
: A photo tube can be tested with a VOM. Set a Simpson 260 or Triplett 630 on the highest resistance scale. Connect the two leads in series with your photo tube. In bright light there will be a reading. Resistance will increase as the tube is made dark. If you don't get a reading reverse leads.
:
: These VOM have a 22 1/2 or 30 volt battery for the highest resistance scale. This voltage is enough to test your photo tube which may operate on 90 volts in the actual circuit.
:
: If you don't have a VOM with high voltage battery use a low current scale on your meter. Test the photo cell with a battery & meter in series.
:
: Photo tubes make neet projects. If you list your tube number I might have specifications?
:
:Norm
:
:
:
:
::This is a hard one to get information on: I want to know how to test the photo cell (tube) in my Victor Animatophone. The audio is loud, but on the variable density sound track it is distorted. This may also be due to that portion of the film being faded, as this would erase all of the faint bars, causing flats in the audio. Furthermore, my other problem is a loss of high notes. The variable area sound track is good, but the variable density sound track lacks much highs. Actually the highs are pretty bad for all film. Sending audio through the amplifier from a CD works extremely well. As for the exciter, I also have the slit adjusted really thin, so this is not likely to hinder high frequency reproduction.
::
::I need to learn a lot more about photo tubes, though, because there isn't much out there on them.
::
::Thomas