Macintosh SE - CRT replacement

[Elio61]

I replaced the CRT (purchased used on eBay) of a Macintosh SE. It turns on but looks like in the photo. Can anyone help me solve? Thank you.

 

[MacTech68]

You need to follow the procedures outlined from page 111 to 123 in the linked pdf below.

If you don't have a plastic hex driver for the width adjustment, DO NOT FORCE IT and DON'T use a metal tool - you will break the component (and they are impossible to buy new).

ALWAYS be careful not to bump the circuit board on the rear of the tube. The SE & SE30 vacuum seal teat is very easy to break.

https://tim.id.au/laptops/apple/legacy/macintosh_se.pdf

 

[Elio61]

Many thanks. It appears to be useful. Just one question: how I can "discharge" the CRT?

 

[MacTech68]

Start at Chapter 6.0 on page 12 and read page 13 here:

https://cdn.hackaday.io/files/1681007191990400/classicmac2.pdf

 

[Elio61]

I followed the instructions but the problem is not solved. The lines are still present on the video

 

[MacTech68]

You need to follow the procedures outlined from page 111 to 123 in the linked pdf below.

If you don't have a plastic hex driver for the width adjustment, DO NOT FORCE IT and DON'T use a metal tool - you will break the component (and they are impossible to buy new).

ALWAYS be careful not to bump the circuit board on the rear of the tube. The SE & SE30 vacuum seal teat is very easy to break.

https://tim.id.au/laptops/apple/legacy/macintosh_se.pdf

Are you sure you followed the above ?

 

[Elio61]

I'll check again

 

[Elio61]

Do you mean this one?

 

[MacTech68]

No, the "External Contrast" and Brightness/Cut-Off.

 

[Elio61]

I have done everything indicated in the guide. the problem is not resolved. The lines still appear on the screen.

 

[MacTech68]

Are you sure the board at the rear of the tube is fitted correctly ? No bent pins ?

 

[Elio61]

I checked. It is mounted correctly

 

[MacTech68]

Also check the cable from the CRT board is snapped into it's socket on the analog board.

Check R25 (470k ohm) Check R22 whilst you're there too (also 470k ohm)

 

[Elio61]

The values of the resistors are the same as you wrote

 

[MacTech68]

What was the symptom before the CRT was replaced ?

Does and did the machine chime when turned on ?

 

[Elio61]

What was the symptom before the CRT was replaced ?
The CRT bulb broke several years ago.

Does and did the machine chime when turned on ?
Yes

 

[MacTech68]

So the lines OR background you see on the screen DON'T change in brightness when you adjust the Cut-Off (Labelled below as 'Brightness Control')?

 

[Elio61]

So the lines OR background you see on the screen DON'T change in brightness when you adjust the Cut-Off (Labelled below as 'Brightness Control')?

View attachment 1745210 View attachment 1745212

No

 

[MacTech68]

Check all resistors on the CRT Neck Board.

Also check:

R20 100K ohm
R21 1M ohm
R26 1M ohm

 

[Elio61]

Couldn't it be the flyback?

 

[MacTech68]

Couldn't it be the flyback?

It could - but a rare case if it is. High tension seems to be working - the raster looks good.

 

[hithere145]

I am having the same issue, but the flyback is fine i just wanna know how to fix the issue

 

[ivannudem]

I heard that the faults of the amplification circuits on the video board/neck board (the small board connected to the neck of the CRT), you may want to swap it with a know good one (please refer to this post from 68kmla https://68kmla.org/forums/topic/23819-typical-video-board-issue-with-all-mac-se-versions-and-se30/)
Typically failure could be the transistor or the diodes (I saw posts on imgur)