Small CD-ROM Drive

VFO || Receiver Range/SWL Information || VFO Stabilization

Small CDROM Used for a Reduction Drive

VFO Tuning with a CD-ROM || Using a Small CD-ROM
Microwave CDROM || Tesla CD ROM || Making a Rough Edge on a CDROM

Kit with small CD

Shown above is the receiver with a small CD-ROM drive used as a reduction drive on the main tuning capacitor. The CD-ROM is held onto the shaft of the capacitor with rubber grommets and is turned by a potentiometer that has had the back removed so it will turn 360 degrees. A rubber grommet is used on the potentiometer to give a firm grip on the CD-ROM drive.

Simple instructions follow showing how to set up reduction drive. Also, the end of the capacitor shaft is a "half-shaft", normally used so a knob will not spin on the shaft, but with this set-up, needs a spacer made with a 1/4" wooden dowel, to make up for the missing part of the shaft, so the CD-ROM will turn evenly on the capacitor.

Parts needed:

  • One small size CD-ROM - if you haven't received a promotional one, a lot of stores like Wal-Mart carry them.
  • Three 3/8" rubber grommets - available at hardware stores. The 3/8" refers to the center hole dimension. A popular brand is "Noble" and the part number is 1123D.
  • One 5/8" rubber grommet (center hole dimension). The Noble part number is 1126D. Take the CD-ROM to the hardware store, as I have seen the grommets marked with all kinds of dimensions.
  • One 1/4" wooden dowel, most likely found at a hardware store in 3' lengths. Inexpensively priced.
  • One potentiometer - an old junk one would be best, but the one in the photograph is a high quality type AB. Watch out for really cheap ones, when you take off the back the shaft will not hold in place. The back of the pot has the stop indention, and that must be removed for the pot to turn 360 degrees. Sometimes you can take the back off, hammer the stop indentation so it is out of the way, and then put the back on. This works with the super cheap plastic ones.
  • A small piece of PCB board that can hold the pot. If you are mounting it in a face plate, you need to drill a slotted hole for proper adjustment against the CD-ROM.

  • Grommet on Capacitor shaft

    Shown here is a rubber grommet on the capacitor shaft, with the wooden spacer made from 1/4" wooden dowel purchased from the local hardware store.

    Cutting dowel stick

    A sharp razor blade mounted in a utility knife works best for cutting the wooden dowel. Measure how long the piece needs to be, approximately 9/16" long, and cut either halfway, as shown in the picture, or the whole piece. Then take the blade and cut through the middle. A slight offset is best, as the spacer can be slightly smaller then the exact half of the dowel.

    Exercise safety! Remember to cut away from you so if you slip, the blade has no chance to get you. I almost cut myself when I sliced the dowel in half. Use a pair of pliers to hold the dowel or clamp it in a small vise. Just be careful!

    Mounting CD on Capacitor shaft

    The CD-ROM is shown being pushed onto the shaft of the capacitor. The 5/8" grommet is placed in the center of the CD-ROM. The grommet should be a tight fit on the CD-ROM. Then two 38" grommets are pushed halfway in from each side. This gives the CD-ROM a lot of stability and grip on the capacitor shaft.

    Mount the rubber grommets on the CD-ROM first. Then while holding the wooden spacer on the shaft, push the CD-ROM with the grommets over the capacitor shaft.

    If you want to make the assembly permanent, a very small amount of rubber glue, or any glue that works, can be used to hold the grommets in place.

    While the grommets are new and flexible, I have not found the need to glue the assembly. I also show this at hamfests I attend and am always taking it apart to show how it is done.

    Aligning drive pot

    A 3/8" grommet is pushed over the potentiometer shaft all the way back as far as it can go. A small piece of PCB material is cut and drilled so the pot can be mounted.

    With the CD-ROM in place, the pot mounted on the PCB material, the rubber grommet mounted on the shaft of the pot, the whole thing is pushed up against the CD-ROM with fair pressure and the PCB is soldered to the ground plane.

    Use only small tacks of solder until you feel you have the right amount of pressure. After the pot is tack soldered on the ground plane, put a knob on the CD-ROM and see how it works. A whole lot of pressure will push the CD-ROM out of place, but just the right amount of pressure will turn the CD-ROM without slipping.

    The edge of the CD-ROM can be sandpapered to get a better grip on the rubber grommet. I have not found this to be necessary in most cases.

    A close-up of the 3/8" grommet on the shaft of the potentiometer.

    The finished reduction drive ready to go.

    VFO Tuning with a CD-ROM || Using a Small CD-ROM
    Microwave CDROM || Tesla CD ROM || Making a Rough Edge on a CDROM

    VFO || Receiver Range/SWL Information || VFO Stabilization

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    Last Update: 7/14/08
    Web Author: David White, WN5Y Free Website Translator