Macintosh Plus CRT Problem

[SpeedM4st3r]

Hi, I recently wanted to get into this world of apple retro computers, and I have some doubts.
I have a Macintosh Plus, which I have some problems with the CRT screen.
Sometimes when starting it, it doesn't turn on, and when you want to start the computer, some lines appear on the screen.
I put some pictures for you to see.
Is there any solution for this?

 

[retr01]

Hello, @SpeedM4st3r!

Welcome to the world of Apple retro computers!

The screen flickering is a warning sign of impending hardware failure in compact Macs. I suspect the analog board (AB) and logic board (LB) need recapping, and solder joints may need resoldering if cracked. Here is an example of cracked solder joints on the bottom of a board:

Even though the capacitors (caps) may look fine, one or more will often fail sooner in a compact Mac on the LB or the AB. All compact Macs are now over 25 years old, with the older compact Macs over 30 or 35 years old. That is why recapping is highly recommended.

Unfortunately, I am not sure if there would be an easy fix. If you are comfortable with soldering, then recapping is something you can do. If not, you can reach out to some professional recappers, depending on your location.

Fear not! @JDW to the rescue! This awesome compact Mac guru clearly explains the recapping on the older compact Macs, including the Plus:

 

[SpeedM4st3r]

Thank you so much for your help!!

 

[retr01]

Thank you so much for your help!!

No problem. You're welcome, @SpeedM4st3r!

 

[Mu0n]

Hi, I recently wanted to get into this world of apple retro computers, and I have some doubts.
I have a Macintosh Plus, which I have some problems with the CRT screen.
Sometimes when starting it, it doesn't turn on, and when you want to start the computer, some lines appear on the screen.
I put some pictures for you to see.
Is there any solution for this?

The left picture is indicative of too high brightness and/or B+ (iirc) voltage sent to the CRT. I used to have old TV sets at our house while I was a kid where the brightness knob could be turned out of "normal" spec and you'd start to see these horizontal sync overscan lines. I've also seen them by direct adjustment while I was working on my Color Classic. There are many reasons that can cause over-voltage and one of those many is the capacitors being out of spec.

Most mac crts have a potentiometer you can adjust with a plastic tool only (because prodding near its vicinity with a metal tool with closeby high voltage is dangerous) but you have to resist going to that solution straight away. It's better to do the easy, basic inspection of anything suspicious looking (including, but not limited to caps) and ruling out other causes of bad voltage level first. If you adjust that important central voltage right away, you might knock things out of spec and out of control and cause more damage to some marginally working components.