70K-2 PTO Lubrication & Assembly

CCA Reflector Thread (19 Apr 2012)

I finally worked-up the nerve and re-lubed the PTOs in my S/Line. All went well, and I found re-lubrication to be the easiest part of the process. Not so easy was re-assembly of the PTO module into the chassis. Of particular frustration, it took more than a half-hour to get the knob shaft’s split pinch roller assembly to mate-up with the inner drive ring. As the PTO is disassembled and later re-assembled, its not something you see as that part if hidden very well.

I also found dial and VFO alignment to be a bit on the difficult side since you’re converging on three targets: 1) electrical end-to-end bandspread accuracy; 2) mechanical end-stop alignment; and 3) absolute dial accuracy. I found it took several iterations of all three to get everything aligned correctly. By contrast, Drake R-4 series PTOs are significantly easier to service and align.

No matter how much reading on the subject I did for preparation, I simply could not get a feel for what was going on. For me, it was a process that required diving in head first, then sorted my way through it, using the on-line references and print articles for further guidance. I found several helpful hints along the way between WB4HFN’s website, the Dennis Brothers’ video produced by Floyd Soo, print articles in the Signal as well as a Collins Service Bulletin. But most importantly, Paul, W8ZO, supplied me with a spare 70K-2 PTO to use as a reference during PTO disassembly.

So, many thanks to Paul for his gracious help.

Finally, a few words about the PTO grease used. Until recently, I’ve been using Lubriplate in the gearboxes of my National receivers. A while back,

Jim, W8ZR, suggested synthetic grease. I wasn’t overly impressed with the result of Lubriplate so, I tried a Valvoline synthetic grease compound when rebuilding a Drake 1A VFO drive. The Valvoline product is “fluffy,” and light much like drywall spackle. I recently used it inside a National NC-101X gearbox after using the dishwasher method to clean the ganged tuner assembly. After using the grease, and DeOxit lubricant on the capacitor rotor clips, operation of the ‘101X is like new with a nice flywheel effect. Icould not get that with Lubriplate. So, thanks to W8ZR for bringing synthetic grease to my attention. It worked very well on the 70K-2 PTOs.

Paul, W9AC