I evaluate a an old Halicrafters radio I picked up at a yard sale for $10. Due to it's poor condition, I decide not to pursue a full repair, but it was an interesting learning experience.
That has an isolated case. You can't measure anything to the case. Usually just a small RF bypass cap to the case. There will be a separate B- buss that is normal ground reference. The can electrolytic is isolated from the chassis. So grounding the cap to the case does effectively nothing. Really, first step is to replace all paper and electrolytic caps as they will leak and cause tubes to draw too much current and burn out coils and transformers (mainly output trans.) Have done an S-40B and S-56. Replacing all the caps does not take that long. Some get away with replacing the power supply caps and the grid caps. My S-40 came that way but still had a leaky bypass cap on the B+. With 3 IF stages should be a decent performer. You should be able to get $20-50 for the radio.
You could do add 2 more caps 40, 40 10 to ground from your filter Cap, then it will be min hum. I have SX-24 did same thing, i did hear it was recieving when you turn main tuning .
Appreciated the PSA at the beginning, Steve. As a curious kid, I used to disassemble all kinds of tube equipment; it's a miracle I didn't kill myself! That receiver probably hadn't been turned on since the Forties.
Hi Steve. I watched all 15 of your videos on the Stihl 290 chainsaw. You are the most persistent person I have ever seen! I have Stihl 029 super that I believe has very high compression. This thing is a bear to pull. Plus, every once in a while it acts like on one of the strokes it’s totally froze. I think it could be pre ignition that try’s to drive the piston in the opposite direction. Pull the plug, pull the starter, and it is free wheeling. I’m 76 years old and not as strong as once was so to start this beast I built what I call a “gorilla pad”. It’s a 2x2 piece of 3/4 inch plywood with fittings to hold the saw down. I stand on the gorilla pad, pull with both hands, and I can get it to run. In your experience with the 290 did you ever come across this problem where it acts like it’s bucking back when you try to start it. It feels like you are jerking on a rope tied to a fence post. Any ideas?? John
Not on that chainsaw,no. However, I did experience that type of problem on a Craftsman mower years ago. As you tried to pull the cord, it would try to rip the rope handle out of your hands. That ended up being a sheared flywheel key that resulted in the flywheel having rotated a few degrees out of position, throwing ignition timing off. I dont know if the same holds true for a 2 stroke with no valves, but I dont see why not.
Thanks for your comments. Your right about it ripping the handle right out of your hand. Once I get it started it revs right up and the idle is a little slow. I haven’t tried to increase the idle speed yet. As for the hard pull , I’ll look through your videos again to see what it takes to get to the flywheel. I don’t think there is any adjustment to the ignition timing unless there is some type of electronic advance in the ignition coil block. BTW, I set the gap with a business card and set up a rig to measure the spark. I was able to get a spark that would jump 1/2 inch. That’s about 30,000 volts. Do you know if there is a spark advance on this saw? The 290 and 029 are almost identical. John
