[TenTec] Argonaut 509 - PTO rebuild parts/instructions needed - still possible? advice/recommendations?

[wb0gaz at yahoo.com]

 Hi Ed,

I got up to reassembly step 19 (bearings in place) and discovered that the vfo shaft was not transmitting enough torque to the core drive rod (not transmitting any torque counter-clockwise, so no return to the CW portion of the band!) so I backed out to step 16 (removing the core drive rod and stuff), cleaned all of the removed parts of grease, and reconsidering the type of grease for the vfo/bearing/core drive/race interface - the Mobile 1 grease (hand on hand) I used might be too slippery for that application. This (torque transmission) was the original problem I ran into, but now (after cleaning and re-greasing the pistol thread and the threads on the core drive rod), the core drive rod turns fine by hand. Another reply suggested Lucas Red "N" Tacky #2 for grease, so I'm going to include that with my next order for "stuff" and use that for the affected area.

The reference to super glue is at step 14 ("Apply a small quantity of super glue on each side of the retainer"); this was the location where glue was found and mentioned in step 9 ("These parts are sometimes glued in place and all old glue must be moved..." - that was the case for this radio.) The glue is just to keep the retainer stuck to the case, and not for the bearings/race interface (that is handled by the viscosity of the grease and pressure between the vfo knob, race and bearings.) After removing the retainer while backing out (so I could re-clean the race and remove the Mobile 1 synthetic grease there), I decided there is sufficient friction fit for the retainer (vs. the housing) that adhesive is not necessary, so I'll skip that on the next reassembly.

I did a century 21 PTO rebuild some years ago (when the kit was available from ten-tec); I don't recall having any difficulty with it, but I did use their supplied (green) grease, and also I didn't have the problem then that I did with this radio, where the VFO shaft initially was not transmitting sufficient torque to move the VFO at all, so that's what stymied me in trying to get past step 4 this time around.

Anyway, thanks for the reply and I'm grateful for any advice as I continue this adventure!

73 Dave WB0GAZ wb0gaz at yahoo.com


     On Saturday, November 21, 2020, 12:36:56 PM MST, Ed - K9EW <k9ew57 at gmail.com> wrote:  
 
 Hi Dave,It sounds like you're making progress, but I've never seen 'super-glue' or '2-part epoxy' mentioned in a PTO rebuild.  Are you sure you need that?  The inner shaft is supposed to make the ball bearings rotate, which in turn makes the outer shaft rotate.  If you need something to hold those ball bearings in place, a dab of lubricant is usually sufficient.
There's a wide range of suggestions for which lubricant to use.  I've used white lithium grease (eventually dries out), synthetic bearing grease (a little bit too viscous for my taste), and - most recently - triflow bicycle lubricant (still going after 2 years).
Too bad those PTO's don't have a grease fitting like cars do (or did).
73,ed - k9ew
On Sat, Nov 21, 2020 at 12:04 PM wb0gaz via TenTec <tentec at contesting.com> wrote:

 Thanks, Bob - my initial search on groups.io didn't use the correct search term - I'll wander over there shortly!

Progress - the problem step (#4) was that ten-tec directed that the PTO setting be fully clockwise before starting work, which would normally push the limit pin close to the back end of the assembly (so pushing in a bit more would expose it to remove the pin). In my case, the (small inner) knob shaft transmits no torque to the (larger outer) core drive shaft so this step (which is critical) wasn't done properly. 

Finally figured out that the core drive shaft would need to be turned manually a few turns (clockwise) to get the limit pin accessible. Although it was pretty stiff, the core drive shaft did turn three turns, and let me resume work. I've since done the degreasing and started assembly (using tiny dabs of 2-part epoxy rather than superglue to reattach the bearing race component to the housing, as it seems superglue would make a future repair job harder.

So, thanks for the replies!

Dave


     On Friday, November 20, 2020, 11:11:38 PM MST, <wb0gaz at yahoo.com> wrote:  

  Found that I had the ten-tec instructions in my file, so proceeded up to a point where I am stuck, so looking for advice:

PTO subassembly housing (that holds the coil and movable parts) removed from the 509 Argonaut without difficulty; all of the various small parts are stashed in small plastic bags.

(referring to the ten-tec instructions on PTO rebuild)

"Step 4. Push tuning shaft (J) back far enough to remove stop pin (H) using long nose pliers. Note the position of this pin as it must be put back in the same hole."

I am not able to push the tuning shaft (J) back (I presume by back, they mean push on it towards the rear of the radio) very far at all - certainly not enough to expose the stop pin so I can safely remove it (I assume the idea is to push the shaft back towards the rear until the stop pin is clear of housing so that the stop pin can be removed.)

The small-diameter inner shaft (where the PTO knob is attached) turns normally, but no movement is transmitted to the gear-reduced larger-diameter outer shaft (where the kHz ring and string wind-up goes), which I think is what actuates the PTO movement forward and backward for frequency change.

As far as I can tell, the root problem is that the "core drive rod (K)" - which is the larger-diameter shaft just behind where the PTO knob is attached - does not turn at all (certainly not by hand, and I've not tried using any tool to turn it because it seems very unwilling to rotate.) Turning this is necessary at step 7 so it can be removed from the assembly housing. I can't work out why it does not turn. What grease I've cleaned up so far seems normal consistency.

I can press the tuning shaft (J) in maybe 1/8", and I see the three ball bearings move back in their plastic housing, but they're not exposed enough to remove them.

Does this ring a bell with anyone? I'm stumped!

Thanks,

73 Dave WB0GAZ wb0gaz at yahoo.com



     On Friday, November 20, 2020, 08:06:37 PM MST, <wb0gaz at yahoo.com> wrote:  

  My Argonaut 509 (S/N 509-3xxx) has been in storage for a long time, and after unpacking it and putting it in line, I discovered the PTO (frequency dial, not the resonator rack) control is largely immobile. I suspect the PTO mechanism grease has gone bad and I'd need to remove the PTO, disassemble, remove the old grease, apply new grease, reassemble, re-install and realign.

All that said, the last time I did this (for another PTO-based analog Ten-Tec transceiver) was some years ago and Ten-Tec at the time could supply the needed materials and instructions.

I presume with Ten-Tec gone that I'm "on my own", so looking here for any advice as to how to proceed. I no longer have the materials (I recall a kind of green grease and a very small metal part) nor instructions (a few photocopied pages, which served well the last time I did this years ago.) 

The 509 seems otherwise to be in good shape, it's just stuck at xx.060 MHz or thereabouts.

Thanks for any suggestions!

73 Dave WB0GAZ wb0gaz at yahoo.com


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