CRT H-size

[fabiodl]

I have this CRT tv which I'd like to use for mister (yes, I am well aware of the dangers of CRTs' high voltage. I mess around with crts since I was 12 and I am still alive ).
I RGB modded it by replacing the OSD ( this is the chip used for video selection).
I have however a problem. The image is cropped on the sides.
I could enter the service menu using this key combination but the only geometry related options are
V-POS,H-POS and  V-HET (which corresponds to the veritical size).
This seems common. this post is noticing width tuning is missing on another panasonic tv (TH-21FA8). Same in this reddit post.
First, I wonder why it is "more difficult" to adjust the horizontal width then the vertical height.

Second is there any hardware mod that could be done to change the width (I imagine adding a pot somewhere) ?
This is the closest TV I found the manual of.
Alternatively there is a submenu named "opt".  According to this article it is " for adjustment at the plant. Stay away from this item, as it means adjustment of all items." but I cannot enter it. Does anyone know how to from experience on similar tvs?

[PKTKS]

First, I wonder why it is "more difficult" to adjust the horizontal width then the vertical height.

Second is there any hardware mod that could be done to change the width (I imagine adding a pot somewhere) ?

First answer:
- Horizontal sweep is designed to be phase locked by the incoming
signal - which is **ALL** horizontal frequency based.

- Usually the vertical sweep is synch'ed by  integrating the horizontal
pulses (equalizing train inside the vertical blank..)

- That signal will also provide synch to the FLYBACK in which
the horizontal scan is the primary signal.

- Vertical is piece of cake - horizontal is not - because it is tied to the FLYBACK


Second answer mostly overlaps the first.
messing the horizontal sweep will undoubtedly mess the FLYBACK PSU
in which you need a great care to not blow anything...

OLD... circuits before these large integrated w/OSD stuff..
usually  have auxiliary coils on the collar/yoke mostly to correct
convergence but also to adjust cushion and size of screen..

new stuff is too way cheap for that..
And THAT stuff w/VCR inside is way too self oriented for that

Paul

[PKTKS]

Checked the manual provided..

YES  anyone trying to change that will have a hard time...

The mains PSU is a "modern"  switched mode standalone
one and the FLYBACK is totally separated having dedicated
integrated (digitally generated) stages..

Cheap highly consumer oriented stuff..
Not suited to be modded although possible...

Unworthy the time effort.

Paul

[fabiodl]

First answer:
- Horizontal sweep is designed to be phase locked by the incoming
signal - which is **ALL** horizontal frequency based.

Thank you very much. You state it is phase locked. Is only the phase adjusted or the frequency as well? I am thinking about editing the sync pulse generation on the FPGA to get a longer sync pulse. Would that do the trick?

Cheap highly consumer oriented stuff..
Not suited to be modded although possible...

When modding it, I definitely had this impression. The tube itself may be not that bad though.

[PKTKS]

First answer:
- Horizontal sweep is designed to be phase locked by the incoming
signal - which is **ALL** horizontal frequency based.

Thank you very much. You state it is phase locked. Is only the phase adjusted or the frequency as well? I am thinking about editing the sync pulse generation on the FPGA to get a longer sync pulse. Would that do the trick?

That changed quite a bit along the first B&W models all TUBE
based ... then to NTSC/PAL  signals all transistor... then...

this kind of highly integrated digitally processed signals..

The Horizontal sweep always had a free run local oscillator
which would be synch'ed w/the incoming broadcasted
signal .. or run free when no locking carrier...

That oscillator in the old times could be adjusted as well...
Introduction of NTSC/PAL sub carriers also introduced
XTAL oscillators - multiple of the Horizontal sweep.

Several variants exists and the digital ones do a hell
of a mess producing the "local horizontal" signal back.

This model incorporates a VCR in which the HEAD(s) signal
is  also XTAL controlled..  it would require a detail view of
how they are being generated...

It seem the FLYBACK is just "drived" by that huge video IC
processor..  hard to say if you can externally adjust the signal..

IMHO? not worthy - simple models would be easier than that.
all circuitry is more or less connected in this model...

Paul