[R-390] Binding in the bushings

[Roger Ruszkowski]

Dave, (agfa at hughes.net) you ask Can someone tell me how to tighten the nuts in the front panel for the 
tuning dials so that they don't bind when tightened. I have the 
mechanism working real smooth, but when I tighten the panel nuts, they 
bind. Same with the ANT control. Dave, the 1968 school house text book answer to your question is "very carefully" Pull the knobs and bushing one more time. The shaft hole through the bushing and the shaft must align. The shafts by design are square to the face plate and I still have some nice bridge stock shares for sale. Look for a burr around the hole in the panel on both sides of the panel. In some previous wrench some metal was jammed up and now it sticks up in the way of least friction.With the last wrench tighten the bushing is pulled to the face plate and cocks when it can not set square to the panel.The bushing can be honed, drilled machined for a better operation.Rotate the bushing 1/8 turn and tighten. Repeat rotation and tighten until you find the spot of best alignment where the error of bushing hole to bushing face has the minimum difference to the error of the shaft being perpendicular to the face plate.  Hang the front panel off the edge of the bench and with the receiver resting flat on the surface of the bench loosen all the front panel screws and let the alignment relax. Start with the 10 32 side bolts and do the small sub chassis hardware last. Loosen the RF deck green screws and giggle the deck a bit for a better alignment.The order in which the RF deck green screws are tightened will torque the RF deck and thus the shaft alignment to the front panel. All these difference values are measured in RCH.It is not a lot but it is the difference between ok and best of class.Use a fiber washer behind the bushing nut to compensate for the not squarely aligned parts. It wrenches up tight enough to hold the shaft center against strong arms but is still at a lower friction level on the shaft rotation.Set the bushing up finger tight where you want them and put a drop of lock tight in between the bushing and the panel to glue the bushing into a low friction position. The glue will set and form the shim needed between the bushing face and the front panel. Elmer's white glue may be a better choice. Once you clean the burrs out and find you still do not have a low friction operation due un straight and miss aligned things, you may want to hone the bushing hole. A bobby pin, length of emery sand paper and electric drill motor will put a polish in the bushing hole quite easily. The idea of sliding a cutting tool onto the shaft and cutting the paint and facing a seat around the shaft hole in the face plate presumes the bushing hole and its seating face are the same true as the cutting tool. Not going to happen. Some face plate holes are still abysmal and have been since their creation. It gauged to specification so keep that wheel a turning and give a little more each day. Over size but not to big not to small not near imaginary center. Some of the bushing faces are minimum size. A pair of thin flat washers used with these bushings offered a solution to keeping the bushing in proper alignment and offering low friction operation. This is a feel skill part of being a hands in Amateur with a R390 receiver. Dave some where you just get a sense of where it needs to be and how to make it happen. Yes the parts are interchangeable but not yet by mindless robots.The difference between it works and it works well is a human touch.You tighten up snug and feel for the coming friction.You find you can bump the shaft, skewing the bushing a RCH and relieve the friction. Know you know which way you need to travel when bringing the bushing from snug to tight.You now bump the snug bushing back from best alignment to some imaginary point.You then wrench the nut tight on the bushing while the pair skew the needed RCH back to a point of perfect alignment. Once a month a maintenance man grabbed all the knobs on a receiver and felt their operation. We expected a proper feel. On the spot repairs and adjustments were completed as needed. Do 10 in one work shift no over time. Six days on and two days off in an eight day week rotate through a day, swing, mid shift schedule. These bushings were always good well aligned and trouble free. As strange as it may sound, I suggest the whole RF deck needs the green screws set loose, the bushing aligned,  the bushing  tightened, and the deck giggled to free behavior. Tighten the internal RF deck screws before you tighten the external RF deck screws along the left side panel. Then redo the bushings again. Seriously the order in which the receiver and decks are wrenched together makes real differences in a receivers friction performance.  This is where you start maintaining a receiver Jay Leno Garage style as opposed to Guy getting an edge on a kitchen knife. I am sorry Dave, but the answer is practice, practice, practice.A mantra is that yesterday this receiver was working. Today it is not so well. Expectation is that only one thing is now wrong with the receiver. Bushing bind.They did not use to bind and have worked well for over 50 years. All three shafts and bushing bind at once. From day one all the R390 receivers have had a chassis setup and alignment. The units are bolted together panels of metal punched within tolerances. We keep it together from maintenance activity to activity. But move a receiver thump and thump and things skew. Do not lift your receiver by the front crash bars. Do what you need to do to get what you have smooth. Some fender washers may be needed. And they may not be uniform in thickness when fit to finish. Respectfully, Roger Ruszkowski