Re: Swapping CRTs

On Sep 8, 1:40pm, Rodger Boots wrote:
> Subject: Re: Swapping CRTs
> Mark Jenison wrote:
>
> > Hi all,
> >
> > Well, I was hoping that CRT pinouts were different between tubes 19VLUP22
and
> > 19VJTP22 because that would explain the problem I'm having, but apparently
they
> > are the same. Maybe there is something else I did wrong, so maybe someone
here
> > can catch my mistake...
> >
> > Anyway, last night I swapped a 19VJTP22 tube into a working G08 chassis.
> > Unfortunately, the original G08 had an internal short and went to the
garbage,
> > so I was looking for a cheap solution. Fortunately, I had a parted out
WG4600
> > chassis laying around, so I used that tube for the experiment.
>
> The only non-repairable short a CRT will normally have
> is a heater-cathode short, and these can be fixed with
> a heater isolation transformer.

I'm sorry; it wasn't a direct short, but there was internal arcing, and the
neon bulbs were lighting. I took it to a friend who had a tube rejuvinator,
and he declared it "dead".

> > Procedure:
> >
> > I unsoldered the original socket on the neck board and replaced it with the
> > WG4600 socket. There is a blue "blob" (cap? resistor?) attached via wire
> > coming out of the socket where the anode wire attaches to it, and I'm not
sure
> > where the other end of the blue blob goes to (gnd? ??), so I left it
unhooked.
> > I think at one point I attached it to ground and it did nothing.
>
> Anode wire coming out of the neck board socket???
> You mean the focus lead that goes to the focus pot?

Correct, sorry.

> > Anyway, I then swapped CRTs, but marked the original placement of the
> > convergence rings, then removed it, swapped yokes, and replaced the rings
as
> > they were. I also swapped degaussing coil and shielding and mounted the
tube
> > on the chassis.
>
> Convergence assembly should have followed the tube
> it was originally on. The magnets (rings) should line up
> with the internal pole pieces of the tube. You might have
> the rings too far forward or backward.

Yes, I simply removed the original convergence rings for a second just so I
could get the yokes swapped, and then returned it to it's original place.

> > Results:
> >
> > I fired up the monitor and got a picture. However, the guns were
overdriven,
> > as you could see all the retrace lines. Adjusting gun gains and cutoffs
was
> > unsuccessful. Adjusting brightness was unsuccessful. Adjusting High
Voltage
> > was unsuccessful. Deflection seemed to be working fine.
>
> Turning down the G2 (screen) pot near/on the flyback
> should bring the brightness down.

There is a focus knob the the HV unit, and three pots which control the HV,
among other things. I did exhaust all means of tuning the picture.

> > Also, color was very screwed up. There appeared to be three zones of
color:
> > 1/3 red on the right, 1/3 blue in the middle, and 1/3 green on the left.
 As
> > lines passed through these zones, they became the color in that zone. Very
> > strange.
>
> Needs convergence, possibly. Needs purity reset,
> definitely. Front rings set purity.

I did not mess with the rings when they were reinstalled. It sounds like you
suggest that I should.

> > So initially I'd say that this doesn't work so well. I can't explain why
it
> > didn't work, so I thought maybe the socket was off by a pin or something
else
> > was screwy. Maybe the heater voltage is incorrect or something. Any
guesses?
> >
> > Anyway, tonight I'm going to try swapping in an Ampliphone tube and see if
I
> > get better results. Maybe someone out there would be willing to swap me an
> > Ampliphone tube for a 19VLUP22?
>
> Don't give up on the tube you have now. Not yet.

Sorry, it's long gone.

While the color could be adjusted, the fact remains that the brightness/gun
drive levels are way too high, as I was unable to reduce or remove the retrace
lines. Maybe the heater voltage for this tube is supposed to be different?
 I'd really like to find a way to use this tube. Maybe I'll just swap the
Ampliphone onto my Tempest monitor and use the Tempest tube for the G08...

----------------------------------------------------------------------
Mark Jenison E-mail address: jenison@cig.mot.com
Cellular Infrastructure Group Motorola--Arlington Heights, IL
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Received on Wed Sep 8 14:38:06 1999