Atari SC1224

[derkom]

By the way, these transistors are 2SD1453 compatible?

https://www.mouser.es/Semiconductors/Di ... u6Z1z0w0x4

No. If you replace that part, you need to go with the same part. That's why it's one of the shaded parts on in the service manual. You can find the right part on eBay, but really you should only be considering replacing other parts after you've solved your vertical problem, which is unrelated to this part.

[qq1975b]

Ok...so let's start with the caps. Thank you.

[Tomswork]

I would also check part tda1170 that it's not overheating because of high current draw from a bad cap or resistor
Be save crt byte

Tom

[qq1975b]

I replaced all the caps but the problem is still there. The V position is still a little lower at its high top.

[sandord]

I replaced all the caps but the problem is still there. The V position is still a little lower at its high top.

What if this was due to a slight tilt or shift of the neck coils? Does the picture look straight overall?

[qq1975b]

The image is like in the picture of the first post. It has a black area on the top of the screen that it can't be corrected using R626 because it is at its top

[sandord]

The image is like in the picture of the first post. It has a black area on the top of the screen that it can't be corrected using R626 because it is at its top

Dang, I just remembered I saw exactly this problem with the SC1224 of a friend of mine. Sounds like a structural design error. Not to say that you can't do something about it... It's just that I don't know it :P

[qq1975b]

I have replaced all the caps on another SC1224 but I have noticed something didn't go well:

One of the SCs if I put brightness and contrast to its max shows a red-brown color. So the red color is predominating in this monitor. On the other hand, the other monitor has de same issue but with the green color. So the images turn to be more green as they should be.
And I haven't touched anything besides the caps.

With two Commodore 1084S I didn't have any issue.

[sandord]

I have replaced all the caps on another SC1224 but I have noticed something didn't go well:

One of the SCs if I put brightness and contrast to its max shows a red-brown color. So the red color is predominating in this monitor. On the other hand, the other monitor has de same issue but with the green color. So the images turn to be more green as they should be.
And I haven't touched anything besides the caps.

With two Commodore 1084S I didn't have any issue.

I think this can be expected to happen. The new parts will have slightly different characteristics and the R/G/B drives needs to be adjusted accordingly. The service manual mentions them on page 6-7 (R323, R303, R343 respectively). Be careful not to increase the overall drive too much.

I'm not saying this will definitely solve your issue but it's the first thing I would check.

[qq1975b]

Thank you. Solved. I had to adjust the Red and Green Cut Off regulators. The Red and Green Drive regulator didn't correct the problem but the Cut Off regulator (next to the others), yes.

Thanks again for the help.