My Kenwood TS-520, which I purchased in 1975 and is 50 years old this year, is still working fine and has never had or needed a repair. I made a SSB QSO on it last week. But being 50 years old means that there could be part failures at any point. Electrolytic capacitors are often the first ones to fail, and many people would automatically replace them after 30 years. If the main power supply capacitors fail, it can lead to other failures, including the power transformer, that probably could only be replaced with a used one, if one could be found.
So with that in mind, I decided it best to replace them before they fail. I ordered a pair of caps from a guy on eBay. There are a couple of videos online, though not always detailed on the caps themselves, often having the VFO removed for the job. Removing the VFO makes replacing the caps easier, but removing the VFO is not simple.
Access to the bottom of the caps is not an issue. But the caps are held in with a clamp on the topside, and located under a PWB, and the plate that mounts that PWB. So the hope was that just removing the PWB and it’s mounting plate would be enough to get the caps out, and the new ones in.
The TS-520 has a number of PWBs in addition to some chassis mounted componentry. There are many wires and wire harnesses making inter-connections between the PWBs, and everything is pretty tightly packed. One of the TS-520s contemporaries, the Yaesu FT-101, used plug-in cards which would make servicing much more pleasant. In 1975 when I made the purchase, and probably made my decision more on aesthetics!
The wiring to that PWB did not have much slack at all, and I needed to unwrap twist-ties to loosen some of the wiring and I was able to just barely get enough room to get at the screws of the clamps and get them out.
I soldered the bleeder resistors and HV caps to the capacitors before installing them in the radio. The supplied new clamps are a smaller diameter than the old caps, and I had to file the mounting holes a bit to get them to line up with the holes in the chassis.
The wires on the bottom for the caps were just long enough to get them attached and soldered, but I had to replace one jumper wire between two of the terminals.
I checked everything over and buttoned the radio back up. Fired it up and luckily it still works. Though there was no noticeable problems before, now I can feel like at least those capacitors shouldn’t suddenly fail.
There are a number of other electrolytic caps in the radio. People sell capacitors kits, but at the moment, I don’t see a need for it. It would be a pretty big job, with many PWBs needing to be removed, and all the wiring that would likely be disturbed or need to be unsoldered. Many connections are made with wire-wrapping which would probably need to be soldered. It could be a job for another time.
