6U5
6U5 is also designated 6G5. Completed sales put the typical price at $43.95 per tube.
Description
The 6U5 is an indicating triode amplifier with a circular fluorescent target and a shadow controlled by an internally connected remote cut-off triode amplifier. It is a high-vacuum, heater cathode type of tube designed to indicate visually, by means of a fluorescent target, the effects of change in the controlling voltage.
Construction
The 6U5 has a unipotential cathode heater rated at 6.3 volts and 0.3 ampere AC or DC. It has a glass bulb with a T-9 envelope and a small 6-pin base.
Ratings
The maximum plate supply voltage for the 6U5 is 285 volts. The maximum target voltage is 285 volts, and the minimum target voltage is 100 volts. Maximum plate dissipation is 1.0 watt.
Applications
The 6U5 is particularly useful as a convenient and non-mechanical means to indicate accurate tuning of a receiver to the desired station. Its application is similar to that of the 6E5, but the 6U5 has a remote plate-current cut-off characteristic.
Operating Characteristics
For a plate and target supply voltage of 100 volts, the triode grid voltage for a 0° shadow angle is -8 volts, and for a 90° shadow angle it is 0 volts. For a plate and target supply voltage of 200 volts, the triode grid voltage for a 0° shadow angle is -18.5 volts, and for a 90° shadow angle it is 0 volts. For a plate and target supply voltage of 250 volts, the triode grid voltage for a 0° shadow angle is -22 volts, and for a 90° shadow angle it is 0 volts.
The series triode-plate resistor is 0.5 megohm at a plate and target supply voltage of 100 volts, and 1 megohm at both 200 volts and 250 volts. At zero grid voltage, the triode plate current is 0.19 milliampere at 100 volts and 200 volts, and 0.24 milliampere at 250 volts. At zero grid voltage, the target current is 1 milliampere at 100 volts, 3 milliamperes at 200 volts, and 4 milliamperes at 250 volts.
| Designation | Evidence | Confidence |
|---|---|---|
| 6G5 | 94 independent documents | strong |
Equivalence is asserted only where the archive's own literature states it directly, in at least 40 separate documents. Tubes that merely substitute in some circuits are not listed here.
| Measure | Per tube |
|---|---|
| Median | $43.95 |
| Typical range (25th–75th) | $23.31 – $68.18 |
| Most sales (10th–90th) | $15.55 – $71.14 |
| Extremes incl. outliers | $7.06 – $77.68 |
| Completed sales | 27 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| Sylvania | $49.99 | $29.99 – $54.95 | 5 |
| RCA | $30.98 | $26.98 – $35.95 | 4 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $60.84 | 17 |
| used | $23.31 | 9 |
Per-tube prices from completed sales, 2026-06-29 to 2026-09-20. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 6U5, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| Tung-Sol | 6U5 | PDF (104 KB) |
| RCA (HB3) | 6U5 | PDF (99 KB) |
| Brimar | 6U5 | PDF (58 KB) |
| Sylvania | 6U5 | PDF (54 KB) |
| RCA | 6G5 | PDF (38 KB) |
Documents held here and used to write this page.
- 6G5 (filed under 6G5)
- THE TUNG-SI INDICATING TRIODE AMPI VOLTAGE IS
1 further designation appears alongside 6U5 in the literature but below the evidence threshold used here, so it is not listed as equivalent.