811A 572B 3-500Z Vacuum Tubes For Sale
We offer the highest quality 811A, 572B, and 3-500 tubes.
How We Test Tubes
All tubes are visually inspected and 100% tested in a high power, high voltage, dynamic tester. The tester measures peak emission, peak grid current, and voltage required to reach the saturated current. For example we test our 3-500Z’s for the peak emission that would allow over 1250 watts peak power output to a load. If a tube does not have that much peak emission, it has a filament reserve emission issue. Tubes are operated through several test cycles to be sure emission is stable and intermittent connections are not present.
The average testing time of about 10-15 minutes per tube is well worth the trouble. This is a much better form of matching and sorting tubes than just running them in a regular amplifier or worse not testing them and relying on the customer to operational test the tubes.
This testing method allows us to sort matched tubes at the high end of the power curve, where the tubes are working hardest and where sharing the load is most important. This is where matching really matters, when each tube shares the heavy load, not when the tubes are just loafing.
We do not use idle current matching (which is mostly useful in class A push-pull amplifiers). We make sure tubes are matched when they are working hard.
For a filament voltage article please visit http://w8ji.com/filament_voltage_life.htm
Some tube sellers will blame short tube life on filament voltage or grid current. We find most tube failures, other than outright gross thermal abuse to tube anodes, actually come from poor tube manufacturing and inadequate testing to weed out bad tubes.
The normal emission life of properly manufactured thoriated tungsten filament tubes is several thousand hours at rated voltage. By far the greatest shortening of life occurs with excessively cold filament operation, where the bulk of life can be lost. The most that might be lost through excess filament voltage might be a few thousand hours out of several thousand.
The normal age-in time is 200 operating hours. During that time it is important to be at rated voltage or above. Do not age in tubes at reduced filament voltage! As a matter of fact, it is not necessary to burn in any tube we sell.
Most tube failures on tubes will less than a few thousand hours operating time are either heat related (which is a dissipation vs time function) or manufacturing defects.
Command Technologies 3-500Z graphite anode for sale.
Directly replaces Ameritron 3-500ZG 380-0500GT. Improved direct drop in for all 3-500Z amplifiers including older Drake, Heathkit, and Henry amplifiers.
The best 3-500 tube being manufactured!
One year warranty against manufacturing defects.
New Command Technologies 3-500 graphite anode tube, also called 3-500ZG and 3-500C for sale. It is a better-tested substitute for the Ameritron 380-0500GT and other 3-500 tubes.
There are currently two plants manufacturing 3-500 tubes. Command Technologies carefully selected the best and most reliable source for their tubes. All tubes are tested both at the source and locally for anode-to-grid breakdown voltage, anode-to-grid and filament leakage current, grid-to-filament voltage breakdown, along with peak grid current while running at peak emission limits with the filament at 5.0 volts.
Matched pairs are selected for similar grid current curves at high power in a peak emission test. Other companies either match idle current or lower drive output power, neither of which truly match a tube used in class AB2.
Because every tube is 100% tested there is no extra charge for matched pairs. We match tubes by the closest curve pair.
Warranty 1 year from date of sale against gas, shorts, and emission loss when operated within manufacturer’s specifications. Breakage or abuse failures are excluded. $279 each plus shipping. Order Now
New Command Technologies 811A Tubes for sale
Fully tested dynamically (breakdown, emission, output power, and grid current) new 811A with 1 year emission and shorts warranty (user anode damage excluded). For a video see YouTube W8JI 811A History
Warranty 1 year from date of sale against gas, shorts, and emission loss when operated within manufacturer’s specifications. Breakage or abuse failures including melted or hot spotted anode are excluded from warranty. 811A $44.95 each plus shipping. Matched tubes no extra charge. Order Now
New Command Technologies 572B Tubes For Sale
Fully tested dynamically (breakdown, emission, output power, and grid current) new 572B with 1 year emission and shorts electrical life warranty (user glass or anode damage excluded).
Warranty 1 year from date of sale against gas, shorts, and emission loss when operated within manufacturer’s specifications. Breakage or abuse failures are excluded. 572B $99.95 each plus shipping. Since these tubes are dynamically matched for grid current at a given output matched pairs, threes, or quads are no extra charge. Order Now
Other Tubes and Tube Sockets
We stock new and used tubes and sockets of many popular and rare types, including EF Johnson sockets.
Tested used mil spec 4CX250R 7580W Tube, mostly Amperex. These tubes are fully tested. 30 day return if undamaged. TEMPORAIRLY OUT OF STOCK
$47 each shipped USA only. Order Now
Tested used YC156A tubes. These tubes are fully tested. 30 day return if undamaged and used in a properly designed amplifier. $950 each shipped USA only. Order Now
Tested new or like new YC108 4CX5000 tubes. These tubes are fully tested. 30 day return if undamaged $1450 each shipped USA only. Order Now
Tested new 3CX1200D7 tubes. Call for price on 3CX1200Z7 tubes. These tubes are new and fully tested but well beyond Eimac warranty. 90 day return if undamaged. 3CX1200D7 NOS $980 each shipped USA only. Order Now
3-500Z style Ceramic EF Johnson $49
Hi-flow metal 3-500Z $79
8877 3CX1500A7 metal and ceramic Eimac $119
EF Johnson 3CX800A7 and similar Compactron style $29
Grid collets for various tubes, including 3CX800A7 grid collet
Also larger and smaller tube sockets, connectors, and chimneys.
Contact for other special high and low power tubes and semiconductors. Thousands of tubes and semiconductors in stock!