2 Dec
2013
2 Dec
'13
3:17 p.m.
On Monday (12/02/2013 at 10:08PM +0000), Tony Duell wrote:
Thanks Tony. Of course I am just teasing you since I have seen previous
postings where you scold folks for randomly swapping parts without a plan.
I fully understand and appreciate that.
In this case, the CRT also had a large amount of burn-in so was highly
suspecious due to that alone. The only thing I liked about it was
that it was amber and all of my replacements are white or green. But,
so goes it.
With the new tube connected and no other adjustments made, the display
is bright and crisp and I have plenty of contrast adjustment with the
contrast control.
I've swapped CRTs in two VR201 and one VT220 in the past couple weeks
so I am getting it down to a science now :-)
In any case, while going down this path I did discover the lack of
documentation for the newer VT220 design and so wrapped the request for
that together with the debug of this particular "dim" unit.
Chris
--
Chris Elmquist
So, I'm
sure Tony will be all over me for swapping stuff before measuring
stuff but in this case, it panned out pretty well :-)
Would I???
One of my _old_ books on TV repair says that. faced with a blank screen,
novices often suspect the CRT. And that while, if the screen is blank, it
is unlikely there are any votlages present that would damage a
replacement CRT, swappign a CRT takes al ot of tiem, and it's best to get
out of that habit :-)
As I said in my first message, I think I would have measured all the CRT
electrode votlages first. The ones on the base pins are under 1kV, so a
noraml multimeter will do. The EHT is goign to be 12-15kV, so you need a
special EHT probe or meter.
If the votlags ahd been normal, I might have tired turning up the
'screen' (first anode) preset to see if I could coax a bit more emission
out of the CRT.