It’s been a pretty fun 5 years where I’ve learned a lot of new things and remembered a lot of things I used to know. The shack has been off the air for the past year, but once I figure out how to get the antenna back up in a mostly stealthy manner, I’ll be back to throwing RF into the sky.
I’m looking forward to many more years playing with amateur radio.
I’ve traced the power supply schematic past the SCR and out to the power transistors that are attached to the big heat sink. This part of the schematic might be a little questionable because a lot of the wires are covered up or obscured by other components and a little harder to follow.
The schematic so far:
I’m up to the control board now. It’s small, but has a lot of wires coming in and out of it. Fortuantely it’s all point to point wiring on perfboard, so I don’t have to follow any PCB traces.
Tracing out a schematic for this power supply has been pretty fun so far. It’s also been a good excuse to learn how to use KiCad.
So far I’ve made it past the rectifier and filtering capacitors up to the power transistors. I’m pretty impressed with the way the innards of this thing are put together. The bridge rectifier part took me a bit to figure out until I realized there were two different stud mount diodes in it.
I’ve come across a couple types of components that took me some searching to figure out what they were (still not quite sure what one of them is). This one in particular is one I haven’t been able to identify.
It’s connected to one of the outputs of the bridge rectifier and the control board at the top. At the bottom it’s connected to an air core inductor and parts that lead to the 2N5886 power transistors. A Google search of the numbers printed on it take me to a single page at a store that has it listed as a rectifier diode.
This is the schematic I’ve cobbled together so far. Things start to get a bit confusing after the rectifier, but I think it’s reasonably accurate.
I wasn’t able to find symbols for everything in the KiCad library, particularly for the connectors, so I just used something that looked reasonable.
This has been a fun exercise so far. The power transistor section will probably take me a while to figure out.
The innards of the power supply look pretty good. Everything looks pretty clean, no scorch marks, and hardly any dust.
Looking at the back panel doesn’t inspire much confidence though. Looks like at some point someone soldered a regular power cable to the original (I think) AC input and covered it with heat shrink. I might have to do something about that when I start working on the power supply.
So far everything looks in pretty good shape. Not sure what the problem with it is (aside from a blown fuse), but before I dive in and start mucking around, I’m going to see if I can reverse engineer a schematic for the power supply. There aren’t any labels on the power supply so I can’t look anything up. Should be a fun exercise.
Spent the afternoon today getting the coax from the entrance panel through the conduit and into the shack. On the first attempt the string I was pulling the coax with broke, so we had to pull some more string. One of the contractors that worked on the house told us a while back that if the string ever broke, tie a new string to a plastic grocery bag, stuff it into the conduit and use a vacuum at the other end to suck it through. Worked like a charm.
With the new string run, managed to get both of the lengths of coax (RG-8X I believe) I had used at the old house through the conduit. One is 75′ and the other is 100′ along with a few extra strings in case we want to pull some more coax. Based on what was left of the 75′ coax hanging outside the entrance panel, it looks like the run between the panel and the shack is around 60-65′. That means there’s a good bit of coax coiled up in the entrance panel right now.
Still a fair bit to do at the entrance panel. I have to decide if I want to trim it (which would mean I’d have to learn how to terminate coax) or leave it coiled up inside the box. Lightning arrestor needs to be mounted, and I’ll have to work out a grounding scheme. Then I need to figure out how to hold the antenna up in the air.
At the shack end, there’s enough sticking out that should make it easy to work with.
I think I’m going to drill a couple of holes in the wall plate for some short SO-239 bulkhead connectors. Then it will be short jumper cables from the radio to the wall.
One step closer to getting the shack back on the air.