Vintage Fisher X-100-B Tube Amplifier Fully Restored

Description

A Fisher X-100-B Tube Amplifier Fully Restored. All electrolytic filter capacitors replaced with Hayseed Hamfest Capacitors as well as the 100MF cap under the chassis. Dual inrush limiters were installed to protect the on/off switch as well as reduce the B+ voltages which run higher with current A/C line voltages. The X-100-B like other amplifiers of it’s era was designed to operate at an A/C line voltage of 115V and the inrush inhibitors lower the A/C voltage slightly to offset the higher line voltage. The B+ rectifiers were replaced with modern silicon diodes. All capacitors in the signal path including the phono pre-amp have been replaced with modern film capacitors. Several resistors in the B+ divider network and in the tone amplifier section were replaced as they were significantly out of spec. I also modified the original Fisher bias setup to allow bias to be set individually on each output tube. Resistors were added to the cathode circuits on each output tube which allows the idle current drawn by each tube to me measured and set individually with the four Bias pots that I installed.
100-ohm resistors were also installed on each output tube screen to protect against potential tube failures damaging the output transformers.
The 7868 output tubes are all vintage tubes, the tone amp and phase inverter 12AX7's are JJ ECC835S and the Phono pre-amp tubes are SOVOTEK 12AX7's. I biased the amplifier at 70% idle current which for this type of amplifier provides good performance and longer output tube life. I will provide printed instructions on how to adjust the bias on the amp but it entails operating the amp with the bottom removed to access the test points. Very high (450V) voltages are present so unless you are knowledgeable about tube electronics I would suggest that you leave these adjustments to an experienced technician. This adjustment is not necessary unless you replace one or more of the 7868 output tubes. I will remove the output tubes for shipment and number them and the chassis so the buyer can insert them into the proper socket upon receiving the amp to maintain the proper bias settings for each tube.
Having said all of this techie stuff the important thing is that this amp sounds absolutely great! If you plan on using the phono input to play vinyl records it would be worth experimenting with different 12AX7's in the phono pre-amp in place of the SOVOTEK's. I have experimented with different NOS and New 12ax7's and there are subtle differences in tone that some folks might prefer.
If you have any questions I will be happy to answer them.