Description
A pair CV491 tubes;1959 Philips production strong and well balanced NOS/NIB
Detailed description
This is a pair Philips Miniwatt CV491, Heerlen, Netherlands oldest production series. With Halo Getters. Very Musical Tone with Long Life! The tubes have excellent test values that match the factory specification very well and balanced systems.
Sand blasted code
The etched date codes on these two tubes are “Gf3 delta 9L” (see photo), meaning that both were made in Heerleen in December 1959. What is special about these tubes is that they have the tube designation “CV491” sand-blasted in big letters vertically on the glass envelope. Heerlen had the practice of putting big sand-blasted production date codes (e.g. “49G” means the 49th week of 1957) on the glass envelopes of their tubes from the mid-1950s to the early 1960s, but this was done only on premium and SQ (special quality) tubes such as the gold-pin E88CC or E80CC. So likely these two tubes were sand blasted to denote that they were specially selected tubes for the military. “In any case, these tubes are as rare as a hen’s teeth“.
Test method & results
The tubes have been tested carefully with the official Telefunken test set-up and our sophisticated test equipment.
Please read our testmethod for the ECC82 tube family.
The measurement results below show that both systems are matched and balanced. And fulfill the factory specs of a new/NOS tube.
| Valve 1
V212 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
9,6 /9,5 mA
2,1 /2,0 mA/V OK |
= NOS / NOS
= NOS / NOS
|
| Valve 2
V213 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
9,8 / 9,9 mA
2,2 / 2,1 mA/V OK |
= NOS / NOS
= NOS / NOS
|
(Telefunken factory specification see test page)
Summarized description
- Tube code: CV491
- Actual Brand*: Philips Miniwatt
- Printed Brand: J-KPB- RA
- Manufactured in: Heerlen; Holland
- Visible Date Code: Gf3 Δ 9L (both tubes)
- Production date: 1959
- Plate Construction: ribbed plate
- Getter Construction: large halo getter
- Print Condition: new; see pictures
- Box: Original boxes
- Equivalent tubes: 12AU7, ECC82, 13D8 , CV4003, CV491, 5814 , 7730, 5963, E82CC, ECC802S
- General test results: NOS
- Quantity of Tubes: One pair
Please read our test and shipping policy before buying !
example pair twin triodes
