5998
5998 has no equivalent designation confirmed by the archive. Completed sales put the typical price at $138.16 per tube.
The 5998 is a medium mu twin power triode used primarily as a passing tube in series regulated power supplies.
## Construction
The 5998 has a heater voltage of 6.3 volts with a tolerance of ±10%, drawing 2.4 amperes at that voltage. It has a medium shell 8 pin octal base (JETEC #88-11) and an ST-16 bulb. The tube is designed for base down mounting and has an average net weight of 2.4 ounces.
## Ratings
The maximum power dissipation per plate is 15 watts, with a maximum DC plate current per plate of 140 milliamperes and a maximum DC plate voltage of 275 volts. The maximum DC heater-cathode voltage range is from -100 to +100 volts, and the maximum grid voltage is 0 volts. The heater voltage range is from 5.7 to 6.9 volts. The altitude rating for full ratings is 10,000 feet. A minimum cathode heating time of 30 seconds is required. The maximum vibration rating is 2.5 G from 0 to 25 cycles per second.
## Characteristics
The transconductance per section is 14,000 micromhos, and the amplification factor is 5.5. The grid to cathode capacitance per triode section is 7.7 micromicrofarads, the grid to plate capacitance per triode section is 18.3 micromicrofarads, and the cathode to plate capacitance per triode section is 2.5 micromicrofarads. The heater to cathode capacitance is 10.0 micromicrofarads, and the capacitance between section 1 plate and section 2 plate is 1.7 micromicrofarads.
## Applications
The 5998 is widely used as a passing tube or series regulator in controlled power supplies because of its high transconductance at relatively low plate voltages. The Tung-Sol datasheet states that the 5998 requires little grid voltage swing to control large currents. It also recommends a cathode warmup time of thirty seconds before plate voltage is applied, and a grid resistor value of 1,000 ohms for each triode section. Heater voltage should be kept as close as possible to 6.3 volts as measured on the tube pins. The minimum cathode resistance per cathode leg shall be 15 ohms or that resistance necessary to provide 10% of the grid bias voltage, whichever is greater. The maximum total grid circuit resistance is given as 500 ohms and 500,000 ohms. For optimum tube life, the bulb temperature should not exceed 130 degrees Celsius; at full dissipation on both triode sections, forced air cooling will be necessary to keep the bulb temperature within rating.
| Measure | Per tube |
|---|---|
| Median | $138.16 |
| Typical range (25th–75th) | $55.91 – $206.32 |
| Most sales (10th–90th) | $34.40 – $255.58 |
| Extremes incl. outliers | $13.50 – $255.58 |
| Completed sales | 20 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| Tung-Sol | $206.32 | $175.18 – $250.00 | 10 |
| RCA | $57.95 | $55.91 – $59.95 | 5 |
| GE | $35.98 | $21.75 – $36.25 | 3 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $117.56 | 4 |
| used | $150.00 | 9 |
Per-tube prices from completed sales, 2026-07-14 to 2026-09-13. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 5998, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| Tung-Sol | 5998 | PDF (300 KB) |
Documents held here and used to write this page.
- TUNG-SOL -