The first stage of fixing up this old transmitter is disassembly. When Johnson built their gear they certainly didn’t spare the fasteners. This thing is held together by a ton of slotted head screws. Took forever to remove them all. Fortunately, the cabinet came apart really easy. The hardest part was removing the front
face. Once I had all the pieces separated I got busy with a bottle of Formula 409 cleaner and paper towels. This works pretty well on most stuff. I also used a tooth brush to really scrub the parts that had a course exterior finish. It didn’t work miracles, but for a transmitter nearing 70 yrs old it’s not too bad.
I now have access to the chassis of the beast. I’m impressed with the overall design, construction, layout, and quality. You can really tell these were built to last. The top side will definitely need some scrubbing, but I don’t see rust or corrosion. Of specific interest is the ganged, gear-driven variable inductor/capacitor tuning unit. Not only is it exceedingly grungy, but it’s not operating correctly. I believe this is the only item of concern up top.
The bottom of the chassis also looks as expected. A little dusty and some spider webs, but pretty clean. Fortunately, no surprises down there. I will have many electrolytic and waxy caps that will need replaced. Since I don’t own a leakage tester I’ll just have to assume they’re all suspect at this age. The worst thing is to let electronics just sit. Even very old components will continue to perform for decades if they’re just used regularly. I’ll also have to do some checks on the resistors as they’ve probably drifted, too. Some components are more critical than others depending on the particular circuit. This will just take some time to research the usual suspects and start ordering.
Fortunately, Johnson made a lot of these transmitters. I’d like to purchase a manual reprint but was able to easily find a PDF on the BAMA website. I’ve found them to be very helpful for everything except Heathkit (because of copyright licensing). I’ve had good luck purchasing reprints from Manualman and others.
Here’s a pic of this big honkin’ oil filled cap. No reason to include it except it’s cool. Just another example of the quality put into these rigs. Hoping to get the chassis all cleaned up and the roller inductor functional again. That will complete the first phase of the project. I think the next part will be more fun. I like working with components better than cleaning stuff up. Stay tuned.