OTHER E M AND T EQUIPMENT
SHOWCASE: General Radio Model 1650A Transistorized CRL Impedance Bridge (1959-1968)
General Radio throughout its history (founded in 1915) is noted for high quality and well built test equipment. One of their weaknesses is over designing leading to expensive equipment with features that may not be fully utilized. This impedance bridge was an industry standard noted for its precision but the high cost and General Radio's resistance to improve, or keep up with tech trends eventually would force them into financial problems. Very expensive (over $1000 in 1960's value). General Radio was one of the earliest developers of the oscilloscope but their resistance to make it better and lower cost allowed others like Dumont and later Tektronix to make a better product dooming General Radio into the shadows of product leadership.
A lot of engineering went to designing this unique display and portable feature of this battery operated impedance bridge. Cute but complicated and requires effort to figure how to setup and transport it. General Radio even designed an intricate battery holder to house the 4 D cells and get access.
Even to open it and set it up for the bench was complicated and tedious!
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Grid Dip Meter
EICO 710 Grid Dip Meter (1960's)
Grid Dip meters are used for checking the resonant frequency of an oscillator for a transmitter or a radio receiver. It can be used to design circuits that oscillate or in servicing to check if the oscillator is functioning. This is accomplished by attaching a coil supplied by the maker, then getting close to the coil of the circuit and watch the meter for a dip in the reading. That indicates a resonance has occurred.
EICO 443 Transistor and Diode Curve Tracer. Purpose of curve tracers are to match and evaluate the quality of a part. Connect this to an oscilloscope with and X-Y input and you can get the dynamic parameters of the part. The curves are a helpful aid to designing and finding the maximum power rating of a part.
Geiger Counter
Issued in the early 1960's to monitor alpha and beta radiation levels in case of nuclear attack. Can also be used as a uranium ore prospecting tool.This model uses a Geiger-Muller tube as a pickup sensor. Readings can be read off the meter in count per minute or heard with headphones. Has a piece of uranium ore attached to the side to be used for calibration.
Specific Purpose Alignment Equipment
Monitor Crystaliner 201 (1950s Mfg MONITOR Products, Los Angeles, CA)
RF Alignment Source for Vintage Broadcast Receivers
RF Alignment Source for Vintage Broadcast Receivers
This RF Generator consists of Crystal Oscillators set to various IF Frequencies used on vintage
Radios for IF peak alignment and has the HI and LO Band Oscillator Alignment frequencies as well. Allows you to put an external crystal for a different frequency and has a built in 400 Hz modulator and variable RF attenuator.
IF FREQUENCIES175, 262, 370, 455, 460, 465 and 470 KHz
RF Carriers600, 1000, 1400 and 1700 KHz
Crystals on Rotory Selector. The 4 Tubes are 6J5 triodes. One is used as a rectifier and the other three are crystal oscillators. The crystal on the chassis is the reference standard unit. These are FT-243 type crystals that date back to World War 2.
My Home Brew Vintage Radio Test Power Supply
1988 Version
Both power supplies have been wired for electrical safety to minimize electrical shock hazard.
Both power supplies have been wired for electrical safety to minimize electrical shock hazard.
ARC 1988 Article
2019 UPDATE BELOW: Beefed up A supply to handle up to 2.5 Amps for battery radios using 0.5 A UV201. Added new panel meters to read values more accurately. Gave front panel a facelift with clearer wording.
In 1988 I built a battery eliminator power supply with A, B and C supplies to handle most battery operated vintage radios. The circuit was published in Antique Radio Classified on December 1988. It was the first time I had an article published. It used analog meters and multi-tap power transformer and incorporated solid state regulators including the Texas Instruments high voltage 3-terminal regulator the TL-783C which I believe is still the only one made. My early design had some errors, being a serious collector for about 5 years. I had the C battery referenced positive (should be negative), some switch position errors and component value changes needed to be made. This version went through several upgrades and I got more experience. Upgrades included changes in panel meters, addition of selectable B and C voltage monitoring, addition of a EMI and safety filter and fixing up the cabinet and making the power supply enclosed.
ABOVE: 2019 Update. Relabeled panel with transfers, and replaced the 117Z6 dual rectifier with 117L7/M7GT. The new supply will encorporate a a vacuum tube rectifier with a silicon diode rectifier for current boost and the 117L7 beam tetrode section becomes a triode series pass or common cathode circuit for better current handling.
2017 Version
Fast track to 2017 and I decided to make a more updated looking one but added some nostalgia into it. The new version, incorporates digital readouts, dedicated A supply to fit all versions of tube filament supplies, built in VARIAC to adjust AC supply for slow stress warmup, fixed B supply to fit all possible B supplies for battery radios and the addition of a vacuum tube rectifier (117Z6GT) instead of a solid state rectifier for nostalgia and delayed B+.
Vacuum Tube Power Supply (JUNE 2019). Designed a power supply strictly for vacuum tube designs. With exception of rectifiers, this unit uses an 0B2 voltage regulator, 6AU6A Voltage amplifier and 2 6AQ5A cathode followers to provide 60-360 VDC 100 mA max for B supply and 0- -106 VDC at 1mA for C supply. Uses a Constant Voltage Transformer for stable input source for tube circuits.
Comparison of the two versions
Circuit Layout 1988 Version Circuit Layout 2017 Version
All my home made power supplies for tinkering
All my home made power supplies for tinkering
Left to right:
+/- 1-20 V Supply up to 3A, +/- 1-24 V Supply up to 1A, 60-360 V Supply up to 110 mA and Vintage Radio Supply & Short Ckt Adapter
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