[TenTec] OMNI D PTO
Gary J FollettDukes HiFi
dukeshifi at comcast.net
Sat Jun 11 01:32:43 EDT 2016
I have not done an Omni D, but all Ten Tec PTO’s are essentially the same. I’ve done a few Century 21’s, Triton’s etc.
The PTO’s are generally pretty easy to get out of the radio and this task does not require much guidance.
If you have some patience, I have a Century 21 that needs this work and I might be able to do a video.
Most important, however, once you get the PTO out of the radio, is to work over a large closed container to catch any parts that unexpectedly fall off the assembly when you loosen things (happens 100% of the time).
After you loosen the screws that hold the black plastic part of the vernier in place on the Aluminum PTO housing, you will likely find that everything is pretty well seized due to the hardened lubricant.
To loosen everything up, gently heat with a hair dryer (not a heat gun as this is too hot). The heat will soften the grease and will allow you to disassemble the vernier assembly to clean it. Don’t force anything as you will most certainly break the brass shaft, which is quit thin at the V groove where the ball bearings run.
The lead screw of the PTO drive, which works with the knob shaft to produce the reduction drive, has the large white piece riding on it. This is actually the holder for the ferrite toroids that make up the permeability tuning slug. Around this rests of coil, which should be unsoldered from the leads going to the PC board for ease in repairing the moving parts.
On this same lead screw are a few other important pieces that serve to maintain a zero lash operation of the lead screw. Make a drawing of how they came out because the reinstallation is not really all that intuitive. A digital closeup photo of the assembly before disassembly can be quite helpful This is a method I use with most mechanical assemblies I repair and really helps as a reality check when reassembling. Make certain you LOOK AT the photos on your PC before you do the disassembly so you know that the photo is good enough to be of use.
The brass center shaft can possibly be worn to the point where the repaired PTO might not work the you reassemble it. That is why the Ten Tec kits came with a replacement shaft. If this is the case, you may be out of luck.
On the last one I did, I put the worn shaft into my lathe and cut a new “V” groove into the knob end of the shaft at the same distance from the knob end as was the original from the other end. Then I put the shaft in backwards with the newly cut V groove on the bearings and I used the worn end for the knob. This worked really well, but, of course, you need a lathe… For those adventurous enough to try this method, I offer that, should you break the shaft while trying to repair it, the shaft is exactly the same diameter as the inner shaft of common dual potentiometers so you can cut a new shaft from one of those if you have one. I have dozens… Hobby shops also have this brass stock.
Reassembly is impossible without first applying the replacement lubricant as everything will just fall out on the floor without the grease to hold the pieces in place. I use either Phil Woods bicycle grease or a high temperature bearing grease for this task.
I hope this little meandering description, done from memory, was of help to you. I don’t have one in front of me right now…
> On Jun 10, 2016, at 11:46 PM, k7mks at comcast.net wrote:
> I'd appreciate comments, from those who have "been there," on the removal, cleaning, lubricating, and reinstalling of the PTO unit in the Omni D. The manual seems a little thin on this subject. There may be others, beside myself, who will benefit from your wisdom.
> Thank you joe k7mks
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