I decided to start the project with the receiver, the HR-10. I think that is the one with the best chance of success. It can also be worked on on its own, independent of the others.
Once the lid was off it was quite obvious why I couldn’t tune properly. The variable capacitor was sticky and hard to rotate. That is not uncommon with variable capacitors that have been left unused for a long time. I’ve worked on two such cases before. I carefully dusted off the inside with compressed air before I took the following picture.
Like much of the inside of the receiver, this one needs a cleaning. Fortunately this capacitor is easy to access. I may even get it out without much effort. The bearings may need new lube of some form. I have worked on two capacitors that looked better but were harder stuck than this one. Those were both hard to access and removal was not a realistic option. In both cases I (slightly reluctantly) used WD-40 and a lot of movement. Which wasn’t easy when the shafts were hard to access. One got very smooth and still works perfectly. The other one was also mostly a success but there are still minute dents in its travel.
For this case I think I will use alcohol for cleaning. WD-40 or any other oil could be used for lubrication. Ball bearing grease may be better if I could find a way to get it in there. I am open to suggestions and warnings. Some people claim that WD-40 may become sticky in the long run. Are they right?
What to do with the sliding contacts? Is there a conductive lubricant?
With the lid off I could turn the capacitor manually from the inside. With a big dipole connected I could receive AM broadcast in the 41 meter band. This indicates that major portions of the receive chain is operational. 👍 Better performance evaluation should be made later.
While the lid was off I also took the opportunity to wash it with dish detergent. That came out very well. Under the dirt the paint was still looking well for its age. Of course there are dents and scratches, but less than you would expect after half a century. I didn’t get all the dirt off so I may try with something else to further perfect the appearance.
I removed the bottom cover too and treated the band switch to some contact cleaner. After moving the band switch back and forth a few times I now have noise on all bands. 👍
The BFO seems dysfunctional, but I heard some scratches when touching the switch. As if it kindly asked for contact cleaner. A little drop and the switched behaved. There is still not much action from the BFO though. The sound changes slightly when turning the BFO knob. I suspect it is off frequency by a large amount. It’s not unexpected that the BFO frequency has changed over the years, but a big offset may hint at a larger underlying problem. Investigation needed.
The dial needle slider has worn groves in the plate it slides on. This can’t be repaired, but future wear can be reduced if I clean and lube it. I want to postpone lubrication until shortly before I put the lid back on. That keeps things cleaner…
As a side project I removed one of the dirty cracked knobs from the transmitter, DX-60 in an attempt to clean it. Results were not good. Next I will give it a round in the dishwasher. Even if I get it clean it needs to be glued together. I am not too optimistic about that. If I can’t get the knobs in order I may have to make new ones. For best appearance I should replace all knobs so they look the same.