Some early models of the GFA-555 MK1 used these vertically-mounted input boards. My existing horizontal board kits could be adapted to work with these amps, but it required fabricating brackets, drilling holes, and adapting the wiring. It was kind of a pain and a bit confusing.
The biggest design challenge for the vertical board model, is the way the original bridge switch is mounted to a small circuit board that is held in place by the RCA jacks. These are not great RCA jacks, and most people will want to swap them for nice chassis-mount types. So I came up with this “Mezzanine board” arrangement with two PCBs stacked together. The first board holds the bridge switch in place, and houses connections for the RCA jacks, LEDs and thermal breakers. Then the input board stacks on top of the mezzanine board, and uses WAGO cage-clamp terminal blocks to connect to the output modules. The input board can be removed and serviced without soldering!
Hi everyone, My GFA-555 MK2 boards are ready to go! Thanks to Jon Morris of Morris Audio in Wyoming for helping me work out the bugs and validate the design. He’s already restored a few customer’s GFA-555 MK2’s with my boards.
Because I’m terrible at self-promotion, here’s a video I should have posted last month!
YouTube blogger XRayTonyB did a three-part video series on repairing a GFA-585 using my boards!
As usual, he goes into great detail on the restoration process, and gives all kinds of generally helpful electronics troubleshooting advice along the way. Tony’s channel is loaded with videos about restoring some really interesting gear like vintage receivers, amplifiers, test gear, etc.
This was not a paid promotion, and there is no commercial affiliation. Tony just bought boards from me like any other customer.
This is perhaps the nicest amplifier I’ve ever restored! A GFA-585; The first of its kind with newly designed replacement input boards. (To fix the infamous leaking capacitor issue.) And I can’t believe I’m saying this, but…
It’s for sale. $1800. Update:SOLD to previous customer, Bill.
Also, I wanted to share what I know about restoring a GFA-585. I hope this is useful to others who are tweaking their GFA-585’s, or installing a set of my replacement circuit boards.