TS-505D/U Vacuum Tube Voltmeter

The TS-505 VTVM, designed around 1953, is one of the finest portable Vacuum-Tube Volt-Ohm meters around, even today. Why would we use a heavy old vacuum tube instrument like this instead of a solid state digital voltmeter? The answers are simple.

Physical Ruggedness. The 505 is built in a tough watertight aluminum case and can withstand physical abuse that would kill a DVM. The internal workings of the 505 are coated with a special moisture and fungus proofing lacquer. It won't rot or rust. It works in extreme heat, cold, humidity, and sand.

Electrical Ruggedness. The 505 is designed to measure up to 1000 Volts DC and is built to last a lifetime, using no electrolytic capacitors. The 7 tubes are run at low voltages and last for decades. Since the device uses vacuum tubes and is completely shielded by a *metal* case instead of a cheap plastic box, the usual electrical, ESD, electromagnetic radiation/EMP and radiological perils pose little risk to it.

Field Repairability. The instrument can be repaired easily by a competent technician. Even if the glass face of the meter is broken and a spare is not readily available, it is a common 1mA movement so that you can get it going in the field. Tens of thousands were made and most parts, including the meters and tubes, are readily available and inexpensive. But this little box isn't going to break in half when you step on it like that $300 plastic meter..

Wide range of measurements:
* Measures from 1 Ohm to 1000 MegOhms (1 GigOhm).
* DC voltage measurement begins at 0.05V with full scale from 2.5V to 1KV
* Zero Center DC function measures +/-1.25V to +/-250V
* AC RMS voltage measurement begins at 0.05V with full scale from 2.5V to 250V RMS from 30Hz to 5MHz.
* AC/RF measurements from 0-40V RMS from 1-500MHz using included RF probe adapter

People object to vacuum-tube equipment on various grounds. Consider these facts:

  • Power consumption: The instrument will operate from 98-132VAC input, from 50-1000 cycles, and draws less than 24 watts.
  • Warm-Up Time: It takes only 10 minutes to warm up and become accurate to 5%. However, you can start using it after about 60 seconds.
  • Weight: The weight is less than 15 lbs. It's not something you want to carry everywhere, but it's perfect for the work bench or to take in the vehicle to a field job.

    Schematic for the TS-505D/U
    Manual (incl. calibration and operator instructions) for the TS-505A/U
    NOTE: The Manual applies to repair and calibration for all models except for very minor differences. Calibration is very simple and usually is not required if the unit has not been messed with.