Tuesday, July 26, 2011


So, the amplifiers at work for our balance that was built in the mid 1940's are run by vacuum tubes. No big deal in that they give a decent amplification of the analog signal to the motors that drive the balance. Problem is, the tubes are getting harder and harder to find. I have a source through a music store for a couple of them that are the same as electric guitar amps. However, one in particular is only available as Russian Surplus. Add to that the fact that the motors used in this beast haven't been made for years and are no longer available. We tried to get a shop to rewind them but the answer was NO from several shops.
So part of the problem is availability of replacement tubes, part of the problem is availability of replacement motors and part of the problem is finding someone who can actually work on the amps. I am tired of dealing with them myself. the old boss was good with them but he is gone now and I am the person that has the most knowledge of them around here now. SCARY!
Sorry, just venting. Did I mention that the room the balance is in is temperature stabilized? Being Texas, it is stabilized at a "warm" temperature so any prolonged troubleshooting involves a profuse amount of sweat. I now offend myself!


  1. I wonder if my dad might be able to help you...he has several sources for rare tubes, and still works on amps, and tube organs fairly often. If you shoot me an email with the tube types, I'll ask him.

  2. I talked to the wife who's an unemployed electronics tech/supply guru.
    She said if you could send her the part number, she could find an online schematic and make a plug-in replacement out of solid state.

    Shoot me an e-mail and we'll see what kind of retro/solid state business she can look at starting.

  3. Thanks, We have a servo motor and amp setup coming as a possible replacement. We're going to install it on a test beam and see how it works then replace the six active beams if all looks good. It will kill two birds with one stone. Since we now use encoders of the end of the motor shaft to keep track of how far the balance weight moves. We will get rid of the encoder and use the feedback from the new servo motor to get position information instead. Should be a cleaner system.

  4. Next time you're hunting for tubes, get a hold of your local HAM radio club. Bump an email to me of the tube you're looking for as well. Buddy of mine here at work has more tubes than you can shake a stick at.