7868
7868 has no equivalent designation confirmed by the archive. Completed sales put the typical price at $39.08 per tube.
The 7868 is a power pentode with a unipotential cathode, intended for use as an audio-frequency power amplifier in Class A1.
Construction
The tube has a 9-pin base with the following pinout: pin 1 connects to grid No. 2, pin 2 to grid No. 1, pin 3 to the cathode and grid No. 3, and pins 4 and 5 to the heater. The heater is rated for 6.3 volts AC or DC at 0.8 amperes, with a voltage tolerance of ±10%. The tube has a T9 bulb with a diameter of 1.062 to 1.188 inches. Maximum overall length is 2.86 inches, maximum seated length is 2.86 inches, and the length from base seat to bulb top (excluding tip) is 2.30 inches ± 0.09 inch.
Ratings
Maximum ratings include a plate voltage of 550 volts, a grid-No.2 voltage of 440 volts, a cathode current of 90 milliamperes, a grid-No.2 input of 3.3 watts, a plate dissipation of 19 watts, and a bulb temperature of 240 degrees Celsius at the hottest point on the bulb surface. During peak levels of speech and music signals, the grid-No.2 input may reach 6 watts. Direct interelectrode capacitances are approximately 0.15 μμf from grid No. 1 to plate, and approximately 4.4 μμf from grid No. 1 to cathode, grid No. 3, grid No. 2, and heater combined.
Operation
The bulb becomes hot during operation, and free circulation of air is essential for adequate cooling.
| Measure | Per tube |
|---|---|
| Median | $39.08 |
| Typical range (25th–75th) | $26.45 – $49.99 |
| Most sales (10th–90th) | $19.98 – $62.38 |
| Extremes incl. outliers | $8.75 – $137.00 |
| Completed sales | 117 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| RCA | $39.29 | $28.00 – $50.00 | 32 |
| Sylvania | $44.72 | $34.99 – $49.50 | 26 |
| GE | $35.00 | $28.95 – $47.00 | 11 |
| Electro-Harmonix | $58.25 | $56.95 – $60.60 | 8 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $49.50 | 33 |
| used | $34.99 | 57 |
| current | $57.83 | 9 |
Per-tube prices from completed sales, 2024-08-09 to 2026-10-17. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 7868, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| RCA (HB3) | 7868 | PDF (423 KB) |
| Sylvania | 7868 | PDF (307 KB) |
Documents held here and used to write this page.
- **Power Pentode**