Nifty power supply circuit boards for Adcom GFA-535 and GFA-545

Improved power supply boards for Adcom GFA-535 and GFA-545!

Hey everyone,

First of all, I’m sorry if I’ve been slow in responding to your messages. Things are super busy; my queue is getting a little nuts, but a lab equipment upgrade is on the way! I’m getting a new scope, function generator, multimeter, distortion analyzer, and a really professional de-soldering station. More on that next week. This should really improve my efficiency, and help me get my customer wait times down.

Speaking of efficiency, it occurred to me that I spend a lot of time modifying the power supplies of Adcom GFA-535’s and GFA-545’s. I address several issues with every refurbished amp.

  • The stock bridge rectifiers lack heatsinks and sometimes overheat and blow out. I have been installing a higher-current bridge, and affixing a heatsink.
  • There’s no AC snubber cap across the bridge, so I have been mounting one underneath.
  • The stock capacitors are the old 4-pin style, which are going extinct. To use the new type with 10mm lead-spacing, either the board or the capacitors need to be modified to fit.
    Soon extinct 4-pin versus now-standard 10mm lead spacing. One reason for the 4 pins is so that it cannot be inserted backwards—a non-issue with modern automated board assembly. If physical stability is needed, glue is used instead, and is cheaper than the extra two pins.

    The new board fixes all these issues, and only takes me 15 minutes to build up. It’s a really nice quality board… double-sided, with double-thick copper traces. The bridge rectifier mounts to the chassis below the board for heat-sinking, saving me the trouble of installing a heatsink, and performing better. It solders in from above. There’s room for larger drain resistors, and bypass caps of 10mm or 15mm lead spacing.

I’m hoping that these boards will actually improve the background noise level of the amp, which is already very low. Because of the flexibility offered by a two-sided board, I’ve managed to tap the the signal ground from a slightly better location than the stock 1-layer board.

These boards will be included with every refurbished GFA-535 or GFA-545, even the MK1 models.

They’ll be for sale soon. I want to make a few minor revisions before I sell them.

Thanks for reading,

Leave a Reply