Katie Bush wrote:Hi Chris,
Just for the record, I followed your thread, in which you tested the CRT from the 'Portarama' as a base line guide, and used the set up chart (chart No.7) as supplied with the Leader, and following the guide inside the lid of the case.
Thanks for the additional info at least we have the test conditions established
Katie Bush wrote:I did notice that any variation in the above voltage settings (i.e. voltage drop as cabin heater cut in/out) can make a significant, though not massive, difference to the result.
Regarding the variation in test results as your cabin supply voltage varies, this is normal and to be expected.
The +/- variation in supply voltage will result in a slight dip +/- of heater volts and in turn cathode emission readings, which again is normal.
You can simulate this by manually adjusting the heater volts yourself. When using the leader I often do a quick check to see how good a cathode is by simulating a low heater supply, say of around 5V on a 6.3V device.
A good cathode will still give very good emission ( albeit lower than at full htr ) with low heater volts. A tired cathode at this heater voltage will not be so good but at the correct 6.3V, giving acceptable emission. A cathode that is well and truly on its way out when placed on 5V will show virtually no emission but at the 6.3V will give some emission. This is effectively a cathode life test, so as you can see a variable cabin supply no matter how little, will effect the heater volts and in turn will significantly vary your emission readings.
I will say on more than one occasion I have encountered quite significant differences in reported emissions when using the B&K and the Leader, mine were about a 30% difference in FSD. The B&K has been reported by one than one person in the TV communities to be less than truthful on B&W tubes so its not just me being biased towards the Leader.
For example I have a NOS 19" colour tube. When run for 10-15mins ( allowing warm-up and stabilisation) the B&K reports it at about 80- 85% FSD, the leader doing the same gives 95-100%. Life tests on both devices show the cathodes to be in superb condition. More evidence the B&K reports lower emission readings than the two Leaders I own. By the way both Leader report identical results so its not calibration. The 30% variance between Leader results and B&K may be due to how the device test and report results.
Based on that fact the B&K reported your B&W CRT's emission low in the red scale and the leader high in the red scale, I would not trust/rely fully on what the B&K reported.
Katie Bush wrote:CRT has previously been tested with a B&K (model unknown) tester and tested as basically dead, so low emission that it was hard to get a meaningful reading.. However, on this LCT910A, it tests being at the top end of the scale - well into the red zone (about level with the "90" mark on the G1 scale).
The above statement is personally confusing, photos would have helped here. Are you stating the Leader is reporting a much improved emission reading than the B&K but it is still in the red? If so Its not reporting a 90% variance more a 30-40% (of FSD) difference. The variance if you take FSD (which you should) of the meter into account, is what I would expect given my past experience with the two testers. Its not as though the leader is stating the emission is good and reading high or even low in the green portion. I would say it is just reading and reporting the low emission differently than the B&K, which fits in with the many reports that the B&K always reports lower emission even on good tubes.
Anyway none of this helps you, the only way for you to be confident and satisfied is to have another independent known good tester. Whatever the readings if all the above is true i.e. B&K reports low emission ( Meter reads low in red section), the Leader reports better emission ( Meter reads higher in red section), the CRT is
low emission. Both CRT tester agree on that, all we are really debating is how low. Out of interest how did the needle behave when you set the G1 and cut-off was it a smooth reaction or did the needle jump about a bit.
I may be going out on a limb here but I would venture to say your leader is probably working OK.