Fisher Model X-100 Stereo Master Control Amplifier

This is an early 1960's Fisher Model X-100 Stereo Master Control Amplifier that uses vacuum tubes. The unit has a metal case as opposed to a wooded case. The unit has two magnetic phono inputs, two auxiliary inputs, and one tuner input. The magnetic phono inputs have a switchable equilization - one setting is for phono, and the other is for tape. These inputs have independent left and right level controls. The two auxiliary inputs and the tuner input do not have level controls.

The unit also has a tape monitor input and provisions to output audio to a tape recorder. Also included are high and low filters, treble and bass controls, and a loudness contour control. Also included is a volume, balance and a center speaker on/off control. Although the left/right channel treble and bass controls are ganged, the treble and bass can be independently adjusted for each channel.

Another feature is a mode control rotary switch. This switch selects monaural phono, reverse, stereo, channel A, or channel B. This switch allows you to reverse left and right, or run channel A or channel B through both speakers. The stereo position is the normal mode.

When I purchased the unit, it was quite dirty and I cleaned it up. Typical of most vintage Fisher stereo systems, the on/off control was defective and someone had removed the on/off control and soldered the wires together such that it is always on. But the unit did work - for a short while. I discovered one weak 12AX7 tube in the preamplifier and I simply exchanged it with one in the phono section to get it going.

I had it playing for a while and then it blew the 3A fuse. The power transformer develped a short circuit from the primary to the high voltage secondary. I removed the transformer and took it apart to see if the short was simple, but I could not fix the transformer. I purchased a Hammond Model 273BX transformer to replace the original defective transformer. The Hammond transformer was too tall so I had to lay it on its side. I had to make three aluminum brackets to fasten the new transformer to the chassis. The picture below shows the new transformer installed. The new Hammond transformer is on the left in the picture below.

The picture below shows the original transformer before I removed it.

The picture below shows the bottom of the chassis and the new transformer wired in on the lower left.

Below is a picture of rear of the unit with the case installed.

The unit works well now and has deep rich bass. It sounds really good. The unit has eleven vacuum tubes. Many of the tubes are original Fisher tubes. If you look closely, you can see the Fisher brand on the GZ34 rectifier tube next to the transformer in the pictures above. Although the appearance of this unit is not exceptional, it does not look bad. It has all of the gold knob caps that are frequently missing. There are several blemeshes on the front panel, but the photos make them look worse than they really are.

Tube Compliment
AF Amp
AF Amp/Phase Inverter
2 x ECC83 or 12AX7
2 x ECC83 or 12AX7
2 x 7247
4 x EL84 or 6BQ5
GZ34 or 5AR4