Stereo and Mono Hi-Fi Equipment
Updated 9/11/07

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1968 Dynaco Solid State Stereo 120 Amplifier Repair Journal (Sept. 2007)

Bell Stereo Tube Amp Page.  (Dec. 2005) This early 1960's amp has 4 6V6's.

Ampex Stereo Console with tuner and phono. (Oct. 2005)  This is a high-quality unit that we will use at our new additional location, the "B" street Studio.  It has 2 separate power amps using 6973 tubes. It appears to work very well. The phono speed change mechanism was jammed, but we were able to use xylene on a q-tip to loosen the old grease. We re-lubricated with LPS-1.
Photos: Cabinet front view.  Rear view of cabinet.  Rear of tuner and preamp.  Tuner and preamp closeup.

Power amp.

Heathkit pre-amp before capacitor replacement.

Heathkit Mono tube type amp and Power supply.


Technics IC output stereo amp.
This amp was found to be unrepairable by another shop but we devised a clever solution to the problem. The amp was overheating and shutting down because the cooling fan was not running. Feeding 3 volts DC to the fan, however, caused it to run. We built a voltage regulator circuit and rectifier on a small circuit board to provide 2.7 volts DC for the fan from a 5-volt power transformer winding.
Photos: Testing the Technics amp.  Chad building the circuit.  Circuit board installed.


Fisher 400 Tube-Type FM Stereo Receiver.
We replaced the 6HA5 tube in the tuner to improve FM reception, added a new power cord, new rectifier diodes, and all new electrolytic and Mylar capacitors.
Photos: Bottom of chassis with new parts. Top of chassis with new JJ electrolytic capacitors.


H.H. Scott Early 60's Stereo Amp Model 233: picture before repairs. This amp received all new Mylar and electrolytic capacitors. Someone had wired up the headphone jack to the phono input, perhaps to use for a guitar, so we re-connected the jack to the original headphone circuit. Picture of capacitor replacement in progress.  Picture of completed unit.

Early 1960's Sherwood Amp: This amp received all new electrolytic capacitors and repairs to the bias supply for the output tubes.

Pictures: Side view during cap. replacement. Picture of 7591 tubes, which mount at an angle to save space.
 

Front View with cover off and new caps, Side view with new caps, Underside of Chassis with new caps


McIntosh Solid State Stereo components: These are part of our shop collection, and are used for testing turntables and tape equipment.

McIntosh Low Frequency Equalizer

McIntosh MR 74 Tuner

McIntosh MA 6100 Amp


XAM Stereo Tube-Type Amp: This amp is similar to the Harman-Kardon A300.

Pictures: Underside of chassis during capacitor replacement.


John working on a Fisher 404 Quadraphonic Receiver

Dynaco preamp: We replaced the capacitors in this amp. Dynaco stereo preamp recap in progress

Dynaco stereo preamp finished; being tested


Tech-Master amp and preamp: Tech-Master Amplifier in test mode. This is a 1950's mono amp that uses 2 5881 outputs and an ultralinear type output transformer. We replaced the capacitors and found it has very good tone quality with good treble response. It consists of separate pre-amp and power amp chassis.

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