- 2025
- Oct
- 9
The Heathkit AG-7 Audio Generator intermission: That’s not right!
Often, when working on an older device, you’ll find part replacements and modifications made by a previous owner to accomplish something. While it’s not always obvious what those modifications were doing, it’s often necessary to remove them in order to restore the device back to OEM functionality.
Case in point is with the Heathkit AG-7 I’m rebuilding. Take these two items:
This is the output adjust potentiometer. Note the 100kΩ resistor.
This is the output Hi/Lo switch. See that jumper wire? There’s also that white telephone-style wire that goes from the switch to the output. This would have been cloth coated originally. Not shown is a messy ground connection here, where they simply twisted three pieces of wire together and soldered it in mid-air.
Here’s the schematic for this portion of the device:
You’ll notice the absence of a 100kΩ resistor across the output pot. I have to assume this was to change the linearity of the output for some reason. There’s also a jumper on the switch, but it’s on the bottom and jumpers the lower half together - not catty-corner like the previous owner had. I’m not sure what they were trying to accomplish with that.
These mods come out, and it gets put back to the way it was. Hopefully, this will reduce the amount of smoke that comes out!
Next part of this series: https://wereboar.com … -part-7-the-rebuild/
Previous part of this series: https://wereboar.com … -removing-everthing/