08-08-2018, 08:04 PM
I have been inventorying some more 45 tubes and have come up with a more easily followed test using my Hickok 533, but, this should apply to most Hickoks of that vintage, 534, 600 and so on.
First, again, the 45 draws over an amp at 2.5 volts causing a sag in the filament voltage which is exacerbated by the additional draw in the "test" condition. The filament voltage drops below 2V. The more "used" a tube is, the worse this is for testing (which makes sense).
I was using the "line" adjustment to raise the filament to 2.5V. Problem is that it also raises the plate and bias voltage. They do seem to track so the tube would not be damaged but the test results are not going to track with the chart.
I found that setting the filament at 3V raised the applied voltage (AC) to 2.5V when the line was set (to the center of the meter). A prolonged "test" will still cause the meter to drop since the load on the PS is still increased. SO, keep your eye on the meter and record the measurement in the first second or so. Results testing 52 used 45 tubes were from 1200gm to 1750gm, probably still a little conservative but inline with expected results.
Setting the filament at 3V (centered meter) gives a plate voltage of 120V and a bias of -20V which is about right (21V would be better but I used the spec. setting of 61. If you really want to be accurate, increase the bias to 63 or what ever gives you the proper bias in relation to plate voltage).
First, again, the 45 draws over an amp at 2.5 volts causing a sag in the filament voltage which is exacerbated by the additional draw in the "test" condition. The filament voltage drops below 2V. The more "used" a tube is, the worse this is for testing (which makes sense).
I was using the "line" adjustment to raise the filament to 2.5V. Problem is that it also raises the plate and bias voltage. They do seem to track so the tube would not be damaged but the test results are not going to track with the chart.
I found that setting the filament at 3V raised the applied voltage (AC) to 2.5V when the line was set (to the center of the meter). A prolonged "test" will still cause the meter to drop since the load on the PS is still increased. SO, keep your eye on the meter and record the measurement in the first second or so. Results testing 52 used 45 tubes were from 1200gm to 1750gm, probably still a little conservative but inline with expected results.
Setting the filament at 3V (centered meter) gives a plate voltage of 120V and a bias of -20V which is about right (21V would be better but I used the spec. setting of 61. If you really want to be accurate, increase the bias to 63 or what ever gives you the proper bias in relation to plate voltage).
