- 2025
- Feb
- 19
The Heatkit AF-1 Analog Frequency Meter, Part 5 - A different approach.
In the last rebuild I did, I simply removed everything that was going to be replaced, and replaced it. See this post for details on that project.
This time, however, I think I’m going to attack the problem from a different direction. This unit has some interesting modifications that directly affect how the unit measures things - those being the replacement of some of the 200Ω rheostats with 5kΩ potentiometers. I’m not sure why, but with a dead power supply there’s no way I can test it.
The logical step would be to fix the power supply first, do some experimentation, and then rebuild the rest with the knowledge gained from those experiments. That’s what I’m going to do.
I originally was going to use some parts I had on hand, but (other than the filter capacitors) decided just to go ahead and get some new, low (compared to the old stuff!) PPM parts. As I needed a couple of other items, I just went ahead and ordered the whole batch from Mouser.
First round is going to see these parts replaced:
3x 10μF capacitors, at least 350WVDC (already have these)
3x 470Ω 1W resistors
1x 2.5kΩ 5W power resistor
1x 2.7kΩ 1W resistor
1x 3.3kΩ 2W resistor
For economy of scale, if there’s a part that’s a 1/2W and I’m buying multiple 1W parts, the lower value will get the higher value wattage. This allows me to get more of a given part, get a price break, and some extras for my parts bin. The 2.7k and 3.3k aren’t really part of the actual power supply, but these provide voltage to the remaining circuits. I’m going to go ahead and do them this round.
The parts being replaced are outlined in red:
The only issue I can see is how to mount the capacitors. I’m not worried about looks, so the can goes - I just need to decide how to mount the new parts.
I should have the components later this week, part 6 involving the power supply is coming soon.
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … -meter-intermission/