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Attention Heath TT-1 Tube Tester owners
On Jun 7, 10:41*am, "William Noble" wrote:
"Jim Adney" wrote in message ... I recently got out my trusty Heathkit TT-1 tube tester to check a bunch of tubes that had accumulated here. I've stopped using its roll chart, because it's starting to show its age, and I assume the roll chart is not replacable. If it IS, I'd love to hear about it. this does bring up an interesting thought, not totally unrelated - with today's inexpensive computer interfaces, why not build/market a tube tester accessory that would plug into a USB bus - all you would need is one of each kind of socket on the unit, and a couple of power sources (filament and plate/bias voltages) - so a set of SCRs to choose filament voltage and apply it to the proper pins, 4 or four cheap D/As to create the voltages (maybe with an HV op amp to create higher voltages), and op amps and A/D with a mux to scan voltages and currents on all the pins of every socket - this would probably take no more than 50 to 100 parts and a small PC board and you could have the tube info read from a computer database and have the test results displayed graphically - transconductance plots, leakage, emissivity, all those esoteric parameters. Done as a labor of love, where the NRE is not amortized, it could be profitable at the $150 to $300 price range - wouldn't this be a good thing? it would take less space, be more accurate, faster and less error prone than using a 40 to 60 year old largely mechanical device. so, who's gonna make it? ** Posted fromhttp://www.teranews.com** Hunh, it should be so simple! I suppose a wide range switching supply for the filaments would work, but it needs to be able to supply between 1V@50mA and 120V@100mA as well as up to 3-4A at around 6V. Likewise you would need 3 variable DC supplies for plate, screen and grid bias as well a source of AC signal for the gm measurements. Also some form of 'free-point' switching to connect the various sources and measure inputs to the socket pins [at up to 4A and 500V]. Then you need the detectors as you say. Methinks the parts cost would be a bit above your estimate. Then the program to run all that stuff and display the results and, finally, creating the tube test data tables. Sounds like a couple of man years work. I am in the process of adapting a Heath IT-3121 output to test tubes, and that simply needs a bias amplifier to drive the control grid, an external supply for the screen and a filament supply. It looks like the IT-3121, an IP-17 and a socket box will do the job along with the bias amp. That's only about a week's work. Neil S. |
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