Adjusting Atari PTC-1426 help

[Steve]

Hi all,

I'd like to adjust the vertical size of the picture for this PTC-1426, as you can see, there are significant black bars top and bottom. I can't find a service manual anywhere though! I have found one for the PTC-1424 which is similar, but not exactly the same, as it has some picture adjustments conveniently located on the rear, where as the 1426 does not.

I looked here: https://docs.dev-docs.org/htm/search.php?find=_M

I suppose I could just start playing around with some of the pots inside the monitor, but I'd rather not be guessing, otherwise I might tweak something I shouldn't!

PXL_20250328_113554142.jpg (242.36 KiB) Viewed 78 times

[rubber_jonnie]

Hi all,

I'd like to adjust the vertical size of the picture for this PTC-1426, as you can see, there are significant black bars top and bottom. I can't find a service manual anywhere though! I have found one for the PTC-1424 which is similar, but not exactly the same, as it has some picture adjustments conveniently located on the rear, where as the 1426 does not.

I looked here: https://docs.dev-docs.org/htm/search.php?find=_M

I suppose I could just start playing around with some of the pots inside the monitor, but I'd rather not be guessing, otherwise I might tweak something I shouldn't!

Edit: I am struggling to upload the image, every time it seems corrupted? Don't know why. I've saved it as jpg twice, then as png... I've uploaded it 4x times now, no dice..

PTC1426_7.png

You'll probably need to look at the vertical size, possibly a pot inside so take all necessary CRT work precautions.

[Steve]

I had a look and found Vsize 60hz adjustable pot (V402 I think)

Much better now:

PXL_20250328_170707151.jpg (350.84 KiB) Viewed 72 times