Frequently asked questionsReturn to home page What is it? It is a little box that you can plug your (compatible) tubes into and find out what they are about, giving real reading in actual calibrated numbers. It is not a clone of an old-school tester, it contains many opamps and regulated power supplies, and directly reads real values. It is not a clone of the VTV characterizer or the George Kaye tester. For example it has adjustable HT and Grid voltage, and reads transconductance, gain and cathode current directly with real numbers. It does not measure noise or distortion, and has no output connection. It is not a pass / fail tester, some degree of user knowledge is required to set up voltages and interpret readings. The data sheet says max 15mA / 300V max (delete as appropriate) for my tube, and the mini TT only goes to 200v max and 10 mA, and not even at the same time! Originally (believe it or not) I didn't have testing to datasheets in mind when I designed the "tester". As a amplifier designer I was more interested in replicating tubes behaviour in circuit, and at the time, I thought 10mA should be enough. This has been bough to my attention as a bit of a limitation however and I agree, but with in the confines of the current design it is not easy to change. These limitations are due to the HT power supply. In most cases, when the tube is in circuit, the actual anode voltage will be less than 200v, (even though HT maybe up to 300V), and the cathode current will be less than 10mA. So it is possible to simulate real circuit conditions (if that is what you want to do!!) How do I do emissions testing? Set the grid voltage to 0 and turn up the HT as high as it will go with out current limit. It is best to find a HT value that works best and then stick with it, to make meaningful comparisons with other same family tubes. My tube has the right pin out but the heater is 1A at 6 volts. Think about making an adapter using a B9A plug, with connections to a regulated external PSU. I want to test a tube that has compatible voltages etc, but the wrong pin out. Think about making an adapter using a B9A plug, see below. Can I test other types of tube? The imp has been designed to test tubes compatible with the ECC83, 12AX7 footprint, however, the electronics inside (with in current limitations) don't care what is plugged in. There is a nice man on e-bay selling reclaimed B9A plugs, so the possibilities are endless. The circuit has been designed to be as robust as possible to shorts between internal voltages, however if the connections are taken out side the box, and other more powerful PSUs are used ( HT or heater), an accident could damage the circuit. This kind of experimentation is not covered under warranty however, so only do it if you are confident in what you are doing. Home last updated Sat Jul 19 07:50:10 BST 2008 |