- 2025
- Mar
- 3
The Heatkit AF-1 Analog Frequency Meter, Part 6 - The power supply.
Since this device came to me with a bad power supply, the first thing I want to do is get that supply back into operation so I can do some further tests on the device. It’s a relatively simple affair, consisting of the transformer, rectifier, filter, and a somewhat unusual voltage regulator tube. There’s nothing going on here you haven’t seen before save maybe the VR150, so let’s jump right in.
Here’s all the parts that were removed:
1x 3-section 10μF capacitor @ 350WVDC
2x 470Ω 1W resistors
1x 470Ω 1/2W resistor
1x 2.7kΩ 1/2W resistor
1x 2.5kΩ 5W resistor
1x 3.3kΩ 2W resistor
The whole reason for this initial exercise, is the original capacitor being bad. The can feels like it has nothing in it at all, and 103Ω certainly isn’t good for an electrolytic capacitor!
The new parts went in to the bottom of the chassis without issues except for the leads being shorter on a few.
Spaghetti comes in handy and is used liberally here.
The top looks a bit different now:
I’m not really concerned with the one capacitor being close to the VR150, it’s a cold cathode tube and doesn’t make a lot of heat. The one close to the 6X5 rectifier may need a heat shield for longer life, however. I think it’s far enough away, but you never know.
A new power cord was added, but I want to check my work before applying power and it wasn’t plugged in yet. That’s coming in the next part, as is some testing with new potentiometers. Stay tuned!
One last thing is the size difference between old and new parts. Here’s some new 3.3k 2W resistors replacing the one next to it. The new ones are almost the same size as the old 1/2W parts, and certainly smaller than the 1W and 2W parts shown. It’s amazing how technology has changed our ability to pack more into a smaller space.
Part 7 on the way, Stay tuned!
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … -different-approach/