Description
1944 Hickok Model 560 (SPL) Western Electric KS-9237 Dynamic Mutual-Conductance Tube Tester with Original Manuals
Item Overview
This Hickok Model 560 (SPL), Western Electric KS-9237, is a portable dynamic mutual-conductance vacuum-tube tester dating from approximately 1944. Hickok Electrical Instrument Company manufactured the tester, while Western Electric supplied and inspected this special version. It was designed for professional telephone, radio, electronics, and military-support work during the vacuum-tube era. The tester appears substantially complete and comes with its original manuals. It contains no explosive or energetic material, but its electrical operating condition is unknown.
Identification and Markings
The Model 560 (SPL) and KS-9237 markings identify this exact Hickok and Western Electric configuration. The inspection marking shows that Western Electric inspected or accepted the unit. The number following that mark appears to be an inspection or control number and should not be represented as the tester’s serial number. The meaning of the “SPL” suffix has not been authoritatively verified.
- Manufacturer: Hickok Electrical Instrument Company
- Western Electric designation: KS-9237
- Model: 560 (SPL)
- Inspection marking: INSP. W.E.Co. 12682
- Related Army designation: Tube Tester I-171
- Equipment type: Dynamic mutual-conductance vacuum-tube tester
- Power requirement: 105–125 volts AC, 50–60 cycles
- Rated power consumption: Approximately 60 watts
- Approximate date: 1944
- Included: Tester and accompanying original manuals
Hickok and Western Electric Relationship
Western Electric used KS numbers for certain products made by outside manufacturers and supplied through the Western Electric system. In this case, Hickok built the Model 560 tester, while Western Electric procured, inspected, and identified it as KS-9237. This arrangement explains why both companies are connected with the same instrument. The Western Electric markings do not mean that Western Electric manufactured the tester’s complete chassis.
Original Testing Functions
The Model 560 was designed to give technicians more information than a simple continuity tester. Its dynamic mutual-conductance circuit measured how well a tube’s control grid regulated current through the tube. This measurement helped reveal weak tubes that might still light up but could no longer provide proper amplification. The tester could display a basic REPLACE–GOOD result or provide a direct reading in micromhos.
- Mutual-conductance ranges: 3,000, 6,000, and 15,000 micromhos
- Tube condition: REPLACE–GOOD meter indication
- Shorts test: Checked for unwanted electrical connections between tube elements
- Gas test: Helped identify internal gas that could disturb tube operation
- Noise test: Assisted in finding noisy or unstable tubes
- Tube coverage: Receiving tubes and small transmitting tubes
- Filament-activity test: Reduced heater voltage by approximately 10 percent to help identify weak emission
Army I-171 Connection
The U.S. Army standardized the basic Hickok Model 560 design as Tube Tester I-171. The War Department’s 1944 equipment catalog identifies the I-171 as a Hickok Model 560 portable tester for small amplifier and rectifier tubes. The catalog also lists the I-171 as part of Western Electric telephone voice-frequency test package X-61821L. A separate Army operating and maintenance manual, TM 11-2047, was issued for the I-171 design in September 1944. No Signal Corps or I-171 identification plate is visible on this KS-9237 example, so the listing does not claim that this exact unit was Army property.
Communications-System History
Vacuum tubes controlled the amplifiers, oscillators, receivers, transmitters, repeaters, and power supplies used in twentieth-century electronic systems. During World War II, these tubes were found throughout military radio, radar, telephone, navigation, fire-control, and test equipment. A weak or shorted tube could lower signal strength, introduce noise, distort speech, or disable an entire circuit. Testers such as the Model 560 helped technicians locate a failed tube without replacing every tube in the equipment.
Military and Industrial Use
The Army’s I-171 version supported maintenance of telephone and voice-frequency equipment, but the Model 560 design could also test tubes used in many radio and electronic systems. Instruments of this type were used at repair depots, laboratories, communications shops, schools, and larger field-maintenance facilities. They were service tools rather than equipment installed inside an aircraft, vehicle, radio set, or weapon. The KS-9237 version could have served Western Electric, the Bell System, a contractor, a laboratory, or a government organization, but the surviving markings do not establish one exact owner.
Fungicidal-Lacquer Treatment
The tester carries a label recording treatment with fungicidal lacquer. This protective coating was applied to electrical parts to reduce damage caused by moisture, mold, and fungus in humid climates. Such treatment was important for communications and test equipment that might be stored or operated in tropical areas. The faded treatment stamp supports a 1944 date, but the coating does not make the tester waterproof or safe to operate without inspection.
Original Manuals
The accompanying original manuals add important historical and display value. Period instructions helped technicians select the proper socket, set the switches, adjust operating voltages, read the meter, and perform the required tests. They also provide useful information about the tester’s controls and supported tube types. The titles, editions, completeness, writing, staining, and physical condition of the included manuals should be confirmed from the product pictures.
Condition and Electrical Safety
This is an untested vintage electrical instrument that appears substantially complete. It may show scratches, paint wear, oxidation, dirt, staining, fading, old repairs, missing hardware, or other signs of age and storage. Original cords, capacitors, resistors, transformers, wiring, and insulation may have deteriorated even when no damage is visible. Do not plug in or operate the tester until an experienced technician has inspected the cord, insulation, capacitors, wiring, fuse protection, and internal components. No guarantee of electrical operation, calibration, completeness, or modern serviceability is offered. Please check the pictures for the general condition of the item.
Ideal For
This tester is a strong display and research piece for collections covering wartime electronics, early telecommunications, military test equipment, vacuum tubes, and American instrument manufacturing.
- World War II communications collections
- Western Electric and Bell System displays
- Hickok test-equipment collections
- U.S. Army Signal Corps exhibits
- Vacuum-tube and antique-radio collections
- Military electronics museums
- Historic communications laboratories and educational displays
Approx length 16", Approx width 14.5", Approx height 6.75", Approx weight 23 lbs.
Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item’s general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.
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