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.

> 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?

> 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.

> 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.

> 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.

> 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.

> ----------------------------------------------------------------------
> Mark Jenison E-mail address: jenison@cig.mot.com
> Cellular Infrastructure Group Motorola--Arlington Heights, IL
> ----------------------------------------------------------------------
Received on Wed Sep 8 14:10:50 1999