- 2025
- Jan
- 2
A Hallicrafters S38-C recap - Wrapup and Bumblebee Capacitors.
I replaced the across-the-line capacitor in this unit with a brand new safety capacitor meant to go across the line. This replaces one of those old multi-color stripe “Bumblebee” capacitors, or bumblebombs as they can be called.
You’ll know these old capacitors because they have a small metal tube on one end with the lead soldered in - for injecting the oil, from what I’ve read. It will also (most likely) be coated with oil. There were other kinds made in this case, like mylar units - but they’re old. Replace it with a modern device actually designed to do the job it’s in place for.
What’s so important about this across the line capacitor that I had to replace it with the filters?
It helps remove noise from the incoming line so it doesn’t get into your radio. But it’s also a part that’s stressed quite a bit as you’re putting AC on what’s essentially a capacitor rated for a DC voltage.
This type of capacitor is an oil-impregnated paper and foil capacitor sealed inside of a plastic shell. While fine for it’s time, the shell cracks and lets oil out, and moisture in. Moisture is bad for a capacitor because water conducts and you don’t want your capacitors conducting. Oil covering the outer shell of this device means it’s been leaking for quite some time.
Let’s check it.
I started by adding new leads (bumblebees have one end that is just a wire soldered into a tube) and shoving it into my B&K capacitor checker. I didn’t feel that the big HP LCR meter was worth getting out for this.
It checks….eh. Yeah, that’s what I’d expect. This thing was likely 20% tolerance, but was probably more like plus whatever minus yeah sure tolerance. But mostly 20%.
This is a good test for my new (old) toy, the Olson TE-189 capacitor analyzer. Testing it, the eye opens nice and wide. The dial indicates about what the B&K meter reads, so we’re right on.
The biggest thing here, however, is leakage.
Yep, 0.2mA of leakage at 150VDC. There should be none that low. This thing is bad bad bad bad bad. At higher peak-peak voltages, this could leak enough to get hot and blow itself apart, or even leak current through something conductive like YOU.
Am I going to toss it? Nope, it’s now a test device. I’ll stick it in it’s own little box where it can leak oil happily until the end of time.
That wraps up the Hallicrafters S-38C Run 4 recap. All of the parts of this series:
A Hallicrafters S38-C recap - Wrapup and Bumblebee Capacitors. - You’re reading it now!
A Hallicrafters S38-C recap - part 4: Doing the work.
https://wereboar.com … rt-4-doing-the-work/
A Hallicrafters S38-C recap - part 3: Layout considerations.
https://wereboar.com … yout-considerations/
A Hallicrafters S38-C recap - part 2: Getting back on it’s feet…
https://wereboar.com … ng-back-on-its-feet/
A Hallicrafters S38-C recap.
https://wereboar.com … rafters-s38-c-recap/
Next up on the bench is an unusual piece of equipment that was obsolete almost when it was new. Stay tuned!