-

Narco 121/22 VOR MHz / KHz gear broken? I can fix it!

Click here to purchase or contact the seller of this item on eBay

Send me YOUR broken shaft/hub. I will repair & return.

Current Price: 125.00 USD

PLEASE READ THE ENTIRE DESCRIPTION

A major problem with the aging Narco 121 and 122 VOR receivers (and com radios) is the internal nylon drive gears split. The company went out of business in April 2011, and support is not available through them. The most common VOR gear failures are:

1) The 21 tooth nylon (Khz, small knob)

2) The 21 tooth nylon (Mhz, large knob)

3) The 21 tooth indexing gear with a 10 tooth detent hub attached. (The second gear after gear #1)

4) The 44 tooth nylon OBS drive gear (very early units with 5 degree dial markings used a 22 tooth gear)

The first photo shows a split Mhz nylon gear, and the same part after the installation of an aluminum gear. You can purchase the repair of either the MHz or KHz gears, or both from this listing. The third picture shows some of the gears I have replaced in just 4 years. They are all broken. Some appear to be OK, but all of them have split. I do not need them, but I do collect them. The fourth picture is a marked up mechanical diagram. The KHz and MHz gears are items 60 and 63, the OBS gear is item 35, and the indexing gear is item 69. Removal of gears #1, #2 and #4 are quite easy. #3 is a pain, to be done only by the brave of heart and involves serious indexing issues.

You will need to send me your broken nylon gear(s) together with the 1/4 inch hollow MHz shaft, and/or the smaller KHz hub. I remove YOUR broken nylon gear(s) and press on a new aluminum gear blank. Since the two gears are not the same thickness, I machine them to be correct. Just SEND ME YOUR BROKEN GEAR AND SHAFT AND/OR HUB and get the aluminum replacement gear pressed on to YOUR part by return mail. I have been asked if I could just ship the gear and let the user install it. I have an assembly jig with press that insures the gear a 90 degree fit, positioned at the exact place required on the shaft, and accurate to within 0.010 of an inch! I also typically have same day turn around.

I also have a few MHz and KHz reworked gears. Also an aluminum replacement KHz gear. See the last photo. The 44 tooth OBS drive gear is not available, but the indexing gear, #69 is.

There is a nice video on how to do this on YouTube. Ebay has removed this informational link, but you can google it by looking for 122 tuning gear replacement.

If your VOR is yellow tagged, it won't be after you open it. While I have been an FCC licensed technician and an EE for over 71 years, I am not FAA licensed.

IMPORTANT: I have received three gear orders that were sent in plain letter envelopes and all arrived empty, ripped open by the postage canceling machine, and a fourth took nine months to reach me. I recommend using the post office's small priority boxes which include tracking and insurance, and currently are $10.40. This small investment protects you against loosing these valuable hubs and shafts. See the last photo…

Do a Buy It Now for the number of gears you want to purchase or have repaired. Pay for each here, then send them together with their hubs and/or shafts to me. My California address will be given to you after purchase.

Bill T.

=================================================

10-13-2016

Sorry for disturbing you, but I've a question about the broken gear: what is the reason that the plastic breaks? Is there any special reason or only the age of the material?

best regards
Ulrich

Ulrich;

There appears to be two reasons. On some gears the gear material looks to be and is perfectly normal. They are not dark, nor do they appear to be brittle. When I measure the diameter of the stainless steel knurled insert that is pressed into the plastic gear the dimensions are all over the map. Some are so large they crack a normal good gear. Some are so undersized that they spin inside a good gear. On the other side, some plastic gears are hard and brittle and crack with just finger pressure. They are usually, but not always, a light tan or darker brown in color. These are virtually all brittle. When you combine an over sized insert with a brittle gear, it will fail. The same for an undersized insert. It will spin occasionally, but will soon wear out. That is why I always recomend changing both gears. Both have to come out anyway just to get at one.

Thanks

Bill Theeringer

W8PEY

Click here to purchase or contact the seller of this item on eBay