especially remembering that the B&K is not the best device for reading old B&W tubes.
Without me finding mine and dismantling it, does anyone know what the FSD of the meters are in a 467? In older CRT testers (e.g. Radar) they were typically 250µA. I'm just wondering if this is what we are dealing with in a B&K - from memory, the meter in a Leader has compression applied towards the upper end of the scale for high-current cathodes which may explain why it's a better bet for later mono tubes, where they're more sensitive before the compression kicks in.
I have some spare meters, so hooked up a test to determine the FSD.
FSD, as good as 200µA.
![20220503 124321[1]](https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/884/11543-202205031243211.jpg "20220503 124321[1]")
@crustytv Thanks for that 👍 So the next question is - are they shunted in a 467? The point I'm making (badly) is that the older Radar (and similar) testers used the meter without a shunt to measure the current between grid and cathode; modern colour CRTs were capable of higher cathode currents as we know so I can't believe there weren't shunts involved.
I can't be sure as I'm having trouble deciphering the cct, but I believe when switched to setting 4, (emission test) 100k is brought into cct for the cathodes.
Reading the service manual that's available on the Web, it suggests that the meters are calibrated to read 0-2mA on emission. The beam current on even a good older mono tube is but a fraction of that. Maybe that's the issue?
Interesting Mike, I sort of feel a little vindicated now for all my bangings on about not using a B&K to test B&W tubes. I had nothing technical to offer other than hearsay to back it up, even though it was relayed to me by the TV engineer I bought the tester from. He stated at the time not to use it to test old B&W tubes and to stick with using my leader LCT-910 for them.
Maybe all those that dumped their B&K 😉 , might now reflect upon these findings.