For your consideration, we have the venerable Marantz Model 7 Stereo Tube Preamplifier that has been fully restored. While we know that some collectors prefer to leave these units completely original, you must keep in mind that this Preamp was manufactured in the 1960's, so we prefer, in part for safety reasons and certainly for sonic reasons, to go through and selectively restore them using modern components. All parts that were carefully removed have been saved and will be included in the sale. They could be reinstalled if one would choose to do so. While the outside of the unit has some scratches and blemishes, it still presents itself very well. Inside the unit is very clean. The faceplate is in very good to excellent condition with only minor blemishes.
This unit came to us in working condition, but had an issue on one of the channels. For sonic and safety purposes, a full restoration was done including the following.
- Removed the Power Supply and preamp chasis
- Replaced the power cord.
- Rebuilt the power supply with custom Hayseed Hamfest capacitors, new old stock carbon comp, and new Ohmite resistors
- Rebuilt the preamp section with Sprague and Vishay axial electrolytics, and Illinois Capacitor axial Polypropylene caps. (All electrolytics tested out of spec and all paper caps had measurable leakage).
- Installed new silicon rectifiers in place of selenium rectifiers.
- High current diodes added in series with filament supply to reduce voltage to specifications.
- CL80 Thermistor added to Power Transformer primary for soft start, and to reduce B+ to nominal levels after swap to silicon rectifier.
- Volume control replaced with Alps 250K.
- All controls cleaned
- All tubes tested