6U8
6U8 is also designated ECF82. Completed sales put the typical price at $8.80 per tube.
Description
The 6U8 is a combined triode and high slope r.f. pentode with separate cathodes.
Applications
The 6U8 is primarily intended for use as a frequency changer at frequencies up to 220Mc/s.
Ratings
The heater requires 6.3 volts at 0.45 ampere. The maximum heater-cathode potential is 220 volts with the cathode positive and 90 volts with the cathode negative. For both triode and pentode sections, the maximum anode voltage is 550 volts at zero anode current and 300 volts under normal operation, and the maximum positive D.C. grid No. 1 voltage is 0 volts. The maximum cathode current is 20 mA and the maximum grid resistance is 1 megohm for both sections. The pentode section has a maximum screen (g2) voltage of 300 volts and a maximum screen dissipation of 0.5 watts. Maximum anode dissipation is 2.7 watts for the triode section and 2.8 watts for the pentode section.
Capacitances
The pentode grid No. 1 to anode capacitance is 0.006 pF, the pentode input capacitance is 5.0 pF, and the pentode output capacitance is 3.5 pF. The triode grid-to-anode capacitance is 1.8 pF, the triode grid-to-cathode capacitance is 2.5 pF, and the triode anode-to-cathode capacitance is 1.0 pF. The cathode-to-heater capacitance is 3.0 pF in either approach.
Typical Operating Conditions
In a typical triode operating condition with an anode voltage of 150 V and a cathode bias resistor of 56 ohms, the anode current is 18 mA, the mutual conductance is 8.5 mA/V, the anode impedance is approximately 5 k ohms, and the amplification factor is 40. In a typical pentode operating condition with an anode voltage of 250 V, a screen voltage of 110 V, and a cathode bias resistor of 68 ohms, the anode current is 10 mA, the screen current is 3.5 mA, the mutual conductance is 5.2 mA/V, and the anode impedance is approximately 400 k ohms.
Characteristics
The grid No. 1 voltage for an anode current of 10 microamperes is -12 volts for the triode section and -10 volts for the pentode section.
| Designation | Evidence | Confidence |
|---|---|---|
| ECF82 | 55 independent documents | confirmed |
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 | $8.80 |
| Typical range (25th–75th) | $4.95 – $13.93 |
| Most sales (10th–90th) | $2.77 – $35.98 |
| Extremes incl. outliers | $0.83 – $63.00 |
| Completed sales | 70 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| Sylvania | $7.58 | $4.74 – $9.75 | 11 |
| GE | $8.61 | $5.62 – $12.72 | 9 |
| RCA | $6.00 | $5.00 – $8.99 | 9 |
| Telefunken | $16.74 | $11.43 – $47.95 | 6 |
| Philips | $12.49 | $12.47 – $17.99 | 5 |
| Tung-Sol | $12.57 | $10.19 – $38.50 | 4 |
| Westinghouse | $9.89 | $4.95 – $13.93 | 3 |
| Raytheon | $8.00 | $3.00 – $50.95 | 3 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $11.79 | 38 |
| used | $5.98 | 19 |
Per-tube prices from completed sales, 2026-06-29 to 2026-09-27. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 6U8, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| Mullard | 6U8 | PDF (122 KB) |
| Mazda-Belvu | 6U8 | PDF (105 KB) |
| Tung-Sol | 6U8 | PDF (79 KB) |
| Brimar | ECF82 | PDF (885 KB) |
| WF | ECF82 | PDF (777 KB) |
| Tesla | ECF82 | PDF (425 KB) |
| RFT | ECF82 | PDF (138 KB) |
Documents held here and used to write this page.
- TYPE ECF82 MINIATURE TRIODE PENTODE FREQUENCY CHANGER (filed under ECF82)
- Triode section
2 further designations appear alongside 6U8 in the literature but below the evidence threshold used here, so they are not listed as equivalent.