Hi all,
I recently bought some TV tubes in the second-hand market, such as 6LU8, 17KV6A, 6HB5, 6JN6, and so on. Then I planned to use them to make a single ended audio amplifier. I looked up the data sheets of these tubes and found that the maximum plate dissipation of 17KV6A was 28W or even more, which confused me. I saw that the plate area of 6HB6, 6JN6 tubes was almost the same as that of 17KV6A, but they only had a plate dissipation of no more than 18W. I don't know why 17KV6A can consume such high power. Can anyone explain?
Thank you!
I recently bought some TV tubes in the second-hand market, such as 6LU8, 17KV6A, 6HB5, 6JN6, and so on. Then I planned to use them to make a single ended audio amplifier. I looked up the data sheets of these tubes and found that the maximum plate dissipation of 17KV6A was 28W or even more, which confused me. I saw that the plate area of 6HB6, 6JN6 tubes was almost the same as that of 17KV6A, but they only had a plate dissipation of no more than 18W. I don't know why 17KV6A can consume such high power. Can anyone explain?
Thank you!
As far as i know, the US manufacturers of TV tubes used the same standardized plate structures for many types as a cost cutting measure.
Beware that US tubes have different sockets from Magnoval.
Beware that US tubes have different sockets from Magnoval.
Shunt regulator vs. horizontal output duty. Horizontal output duty is derated quite a bit - you can go somewhat over 18 watts as a linear amplifier, provided vg2 is kept under control (keep it below rating).
Also beware novar is NOT magnoval. For the time being anyway, vacuumtubesinc.com HAS novar sockets. They fit 6LR8 perfectly. Bought some tried ‘em. Hope they can keep getting them.
Also beware novar is NOT magnoval. For the time being anyway, vacuumtubesinc.com HAS novar sockets. They fit 6LR8 perfectly. Bought some tried ‘em. Hope they can keep getting them.
Quite. A. Bit. I did an audio project with push-pull 6BQ6GA finals. These are horizontal deflection types with a PD rating of 11W (same as the 6V6 or 6AQ5). I biased them hot with a static PD= 17.5W -- 59% over the rating. This hasn't been a problem as the amp is still on the original 6BQ6s since Ought 7. Audio isn't a "brick on the key" mode, unlike horizontal deflection duty, so you can bust the specs by quite a margin.
I found the RCA gray plate 6BQ6s will show a trace of color with 70mA @ 350VDC while the Sylvania black plate 6BQ6s do not. Staying within the spec sheet rating with IP= 25mA made for noticably worse sonic performance, so I stuck with the hotter biasing that reduced x-over distortion, and made for more Class A1 power. Less distortion predicted from load line analysis worked out in practice.
Deflection tubes are indeed specced rather conservatively. A Soviet 6P41S (6П41С) states in the datasheet:
Maximum design plate dissipation - 12W
Minimum plate dissipation - 14W
I run them at 20W, they dont break a sweat. Others see redplating after 25W. Go figure 😀
Maximum design plate dissipation - 12W
Minimum plate dissipation - 14W
I run them at 20W, they dont break a sweat. Others see redplating after 25W. Go figure 😀
I alluded to this in my first reply, if I understood "Tubelab" correctly, General electric and a number of other manufacturers chose to use the same 22W plates for sweeps for most models after a certain date. As a cost cutting measure.
Black VS red plates has a slight difference in how well the anodes can get rid of heat. Black plates are carbonized nickel, and grey plates is indicative of aluminium cladding.
From what i gather, grey plates where cheaper in production.
Black VS red plates has a slight difference in how well the anodes can get rid of heat. Black plates are carbonized nickel, and grey plates is indicative of aluminium cladding.
From what i gather, grey plates where cheaper in production.