Quote:
Originally Posted by Yamamaya42
I have a bk precision 490b, but the damn thing lies to me...
It always worked fine with all sorts of mono tubes, and 25vxxx tubes and projector tubes, and so on.
But when I hooked up my 21fjp22 that had been it storage forever,, VERY LOW emissions, scared the hell out of me, I thought the tube went dud in storage, took me a while to spot what was going on...
heater V @ 4vac, barely, it could not put out enough power for the heaters in the CRT. 
So, I got a 6v 3amp xfomer and it came right up into the "really good" range on all 3 guns...
But, WTF? not enough power to light up a roundie? come on BK... |
I'm guessing the 490 has only a switch to set heater voltage.
Different CRTs have different heater current which load the filament transformer differently...my 466 has a continuous heater adjustment knob and you set it by reading the heater voltage on one of the scales of it's meter....a CRT can draw as much current as it wants and you will still be feeding it the right voltage even if you have to set the coarse heater adjustment switch to a higher a range... Some of the low current 6.3V monochrome portable CRTs barely need adjustment of the heater pot, but a power thirsty roundy will need it set fairly high.