I prefer to keep it short as I’m not fond of writing much these days. It’s partly why I’ve been out of touch for a while. Nevertheless, my projects continued, and I’ve restored an old 1960 Magnavox 88-02-00 Tube Amplifier.
Restoration
This involved replacing all the old paper capacitors with contemporary equivalents and updating the resistors to better match the schematic. Additionally, I installed a volume knob, a two-input switcher for potential Raspberry Pi streaming, input RCA jacks, and output speaker posts compatible with both screw-on and banana plugs.
To ensure compliance with modern standards, I added a three-prong 120V socket typically used in power supplies, a fuse, a lighted switch, and completely new wiring. Furthermore, I incorporated an inline resistor to reduce the voltage from 120V to the original 110V from 1960, thereby preventing an increase in power to the circuit which would adversely affect longevity.
Special Change
The primary modification I made to this amplifier was swapping out the 6v6 tubes for their lower voltage equivalents, the 5v6. This is due to the fact that 6v6 tubes are typically much more expensive than 5v6 tubes.
Per the datasheet, the sole difference between them lies in the operating voltage and current consumption. Therefore, I simply installed an inline resistor to reduce the voltage from 6.3V down to 4.7V.
This adjustment makes acquiring new old-stock tubes not only easier but also more cost-effective, without any theoretical difference in sound quality.
Gallery
Since pictures speak better than words…
The 3D printed parts:
https://www.thingiverse.com/thing:2799993
Circuit
Conclusion.
This project has become a personal favorite. It’s astonishing that this device, after 58 years, still functions perfectly. The sound it produces is not only crisp and clear but also loud enough to fill an entire room.
It’s incredible to consider that today, what once took up so much space in plastic and metal can now be condensed into an integrated circuit as small as a fingernail. This truly speaks volumes about the potential future advancements in technology.
For now, I cherish the opportunity to experience a slice of history.
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