[GreenKeys] CRT Left side char distortion...

[Chris Elmquist]

On Tuesday (09/15/2015 at 03:19PM -0400), Keith Densmore wrote:
> Good thoughts, and I thank you. The problem is made worse by the fact that Hal
> rarely provided schematics for his stuff. The monitor section appears to be a
> Japanese sub assembly but I have no schematic for it.
> I
> don't suppose anyone would by some miracle have a schematic for the Hal Telereader 6850? Or just a schematic of any greenscreen monitor, I'm
> sure they are all similar.
> I'd try replacing/checking caps if I had something to go by.

I can't offer help with a manual but I did track down the vintage
(1981 perhaps),

http://www.eham.net/reviews/detail/5857

but indeed it was built in Japan by "Comax" so you need to track down
a Japanese monitor schematic I suppose.  Not sure what would be similar
from that era?

Neat unit though.  Curious what microprocessor is in it when you get
the cover off...

Chris NØJCF

> Original Message:
> From: Chris Elmquist <chrise at pobox.com>
> To: Kenneth Gartland <trnsrme at gmail.com>
> Cc: <GreenKeys at mailman.qth.net>
> Sent: 2015-09-15 3:05:54 PM
> Subject: [GreenKeys] CRT Left side char distortion...
> 
> 
> I had similar thoughts as Ken but also the possibility that the CRT
> may need a degaussing. Not sure when degaussing coils became integral
> and automatic but it's
> possible that while this tube "held down the
> closet", it got magnetized
> externally in a non-uniform way and this is
> now distorting the image.
> 
> I have seen this when a video monitor was stored next to the large steel
> chassis of another piece of equipment and this warped the image after
> that CRT was pulled out and powered up.
> 
> If the gear has an integral degaussing coil and does it automatically
> at power up (the image will wiggle right after power up if so) then you
> can probably discount this idea.
> 
> https://en.wikipedia.org/wiki/Degaussing
> 
> Chris NØJCF
> 
> On Tuesday (09/15/2015 at 02:51PM -0400), Kenneth Gartland wrote:
> > Hi all...
> >
> >
> Keith's problem of char distortion, is likely linear sweep as mentioned
> > already, but maybe as simple as a 'Deflecting
> magnet" having dropped
> > (Unglued) from the CRT area just ahead of the yoke ass'y...
> >
> > Many of the older, especailly cheaper, CRT's used as computer monitors,
> > used these stick on magnets to cure all kinds of deflection issues, especially
> > in the corner areas of the tube...
> >
> > Some magnets were held on by a silicone seal adhesive, or equiv., and some
> > were fastened with an adhesive pad...
> >
> > Best for Keith to check in the base of the CRT area to see if this is
> > the case...
> > They usually fall off and go straight down, where you can't. get at
> > them of course!!
> >
> > Almost forgot!...If the CRT has 'Centering' tabs on the CRT neck, moving the
> > tab up or down on the left side mite clr the problem...Use an orange stick or
> > some other insulated tool to carefully move the tab...Lotsa HV in
> > there so one has
> > to be carefull!
> >
> > Hope this helps a bit...
> >
> > Cheers!
> >
> > Ken VE3-HMQ
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> --
> Chris Elmquist
> 
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-- 
Chris Elmquist