Hey everyone! A few weeks ago I received my pair of Fairchild 255 amplifiers, which had some previous work done to them. When popping the covers off I knew everything had to go since the craftsmanship was of low quality. Huge mundorf capacitors were installed, the gain pots were removed, different rca jacks were installed, the bracket that holds the balance pot in place was gone to fit the large capacitors, the soldering was poor, among many other things. So I tore everything out to bring it back to an original state.
Here is what they looked like when I got them.
Since those mundorf filter caps installed are fairly expensive, I of course kept them for another project. I did keep the mundorf silver coupling capacitors in the amps since they are nice, I just cleaned up their placement. A new can capacitor was installed, along with sprague atoms for the bias supply.
The resistors in the power supply were replaced with metal films and wirewounds, and I decided to replace the majority of the other resistors (since almost all were out of spec) with NOS Allen Bradleys, to keep the original sound, and the original look. I was able to match the critical resistors within 2%. I had never used Allen Bradley resistors before, but I must say I am pleased!
Since the gain pot was gone and replaced with a 100k resistor, I put a new one in. The other 2 pots (Bias and Balance) both originally bolted to a mount. Since both amps were without the bracket for the balance pot, I fabricated a new one. I was lucky enough to find the original RCA wafer jacks that fairchild used, and installed them, replacing the isolated jacks the previous owner installed. I also used a shielded cable for the input, which Fairchild did not originally use in the 255, but they did in the 260.
I apologize some of these pictures are a little fuzzy.
Diode replaced selenium rectifier for Bias supply
I obtained a matched quad of black glass Brimar 6L6 tubes, which are fantastic, and some very early 1950's philips ec92 tubes. Currently rolling some Brimar 6067 (Yellow T 12AU7)
Overall I am very happy with how they turned out. They really sound fantastic, and are super quiet, absolutely no hum or noise at all. Enjoy!
Here is what they looked like when I got them.
Since those mundorf filter caps installed are fairly expensive, I of course kept them for another project. I did keep the mundorf silver coupling capacitors in the amps since they are nice, I just cleaned up their placement. A new can capacitor was installed, along with sprague atoms for the bias supply.
The resistors in the power supply were replaced with metal films and wirewounds, and I decided to replace the majority of the other resistors (since almost all were out of spec) with NOS Allen Bradleys, to keep the original sound, and the original look. I was able to match the critical resistors within 2%. I had never used Allen Bradley resistors before, but I must say I am pleased!
Since the gain pot was gone and replaced with a 100k resistor, I put a new one in. The other 2 pots (Bias and Balance) both originally bolted to a mount. Since both amps were without the bracket for the balance pot, I fabricated a new one. I was lucky enough to find the original RCA wafer jacks that fairchild used, and installed them, replacing the isolated jacks the previous owner installed. I also used a shielded cable for the input, which Fairchild did not originally use in the 255, but they did in the 260.
I apologize some of these pictures are a little fuzzy.
Diode replaced selenium rectifier for Bias supply
I obtained a matched quad of black glass Brimar 6L6 tubes, which are fantastic, and some very early 1950's philips ec92 tubes. Currently rolling some Brimar 6067 (Yellow T 12AU7)
Overall I am very happy with how they turned out. They really sound fantastic, and are super quiet, absolutely no hum or noise at all. Enjoy!