A few pictures of a GFA-555 MKI without “The Works”

Hey internet, I just finished refurbishing this GFA-555, and the customer opted to go without the BFA-555 Smart Soft-Start Power Supply, so if you’re wondering what you get without this option, here it is! I do install some Capacitor Hats to replace the crusty originals. The original power supply capacitors were replaced with Kemet ALS30, 22,000uF, which is about as big as you can go without a soft-start. (Or the switch will spark too much and the fuse may blow due to the in-rush current.)

Invoice on this one was $1210.

How to build a Test Jig, or Test Fixture, for your Printed Circuit Boards

Printed circuit board+Pogo pins=Test jig.

Printed circuit board test jig, or test fixture

Every circuit board I sell need to be thoroughly tested, and measurements taken that should agree with expected values. Tests are chosen to show up any errors I might have made in the board’s assembly.

Test jig, jigging and testing.
  • Gain. I use 0.1% tolerance resistors in key parts of the circuit, so gain should match within 0.01db from one board to another.
  • DC operating points, such as the drive voltage to the output sections, DC offset, DC servo output, and bias voltages
  • Distortion; it should match measurements from other boards, all the way up to full-scale output.
  • Current running through various branches of the circuit.
  • Functionality of indicator LEDs

Here’s how I build my test jigs.

Continue reading How to build a Test Jig, or Test Fixture, for your Printed Circuit Boards

EBFA-565 versus BFA-565 (Validating a new design)

Launching a new product is a lot of work! I’ve been working on these new boards for the Adcom GFA-565 for about six months now. (Now available here.)

This is the last step before I consider it fit for saleโ€”design validation. It has to perform at least as good as the previous version, and it has to deliver on the usability improvements. I need to install it into an amp, and not only test its electrical operation, but the user experience of installing it.

Continue reading EBFA-565 versus BFA-565 (Validating a new design)