Twitching, Shrinking Screen
Posted in: 2600
Posted: 2016-11-30 14:20:54

QUESTION:

The internal monitor on our SE/30 has started acting strangely. At seemingly random intervals, the picture momentarily shakes and shrinks toward the center, then snaps back to normal size. Is this the beginning of the end for the monitor component on this six-year old machine (used eight hours a day during that period) and is this time to replace it, or is there likely to be some easily correctable connector problem? The Dead Mac Scrolls doesn't seem to address a problem like this.
ANSWER 1: I had essentially the same problem occur on an SE, and since the two machines are so closely related, it may be the cause in your case - bad solder joint. Solder tends to get brittle with age, probably caused to an extent by the heating and cooling that takes place. That's why you might notice the problem gets better or worse as the machine heats up.

I was lucky that the solder problem was with one of the large wires that runs from the analog board, the one that's mounted vertically on the left facing the front of the machine. About all you can do is take a soldering pistol to each of the solder joints and heat them up. Have a roll of solder handy in case what's on the connection gets stubborn and won't melt down real well.

If you don't feel comfortable using a soldering pistol, you might want to find a friend that's experienced. Also take care since there's a high amount of voltage handled through those connections to the CRT that can give you more than a bit of a jolt. Easiest way to lessen this chance is by discharging the CRT. About all that's needed for this is a medium flat blade screwdriver and a piece of decent sized wire with alligator clips on each end. Radio Shack sells them in a bundle of different colors.

ANSWER 2: Sounds as if you need to do some soldering on the video/analog board. It's probably at the plug that connects the deflection yoke to the board. Those connections can shake loose over time due to the high power and frequency of the horizontal deflection circuitry. I've seen similar problems on quite a few machines (including my own SE/30, now semi-retired). My machine had a bad plug/socket - lots of internal arcing which caused flickering before I replaced both the plug and socket. I've seen other plug/socket situations where the arcing was so bad that the plastic had melted and fused together.


QUESTION:

I have a Mac SE/30. When I start the unit up, the right side of the display shakes violently. It then quiets down only to become unstable at some random later time. Could anyone give me an idea as to why I might be having this trouble?
ANSWER: According to Larry Pina in The Dead Mac Scrolls, that symptom is often associated with a loose ground wire chassis connection. Check that the green wire with the lug on it attached to the power supply is screwed down tightly.

QUESTION:

My trusty old SE has had problems with a twitching screen image for quite some time, and just before Christmas it broke down altogether. The image is now reduced to a vertical stripe in the middle of the screen. I brought it to a local dealer, and he said: "Yeah, sure, it's a capacitor on the 'analog card'. It'll cost you 1,300 Swedish kronor (approx $180) to fix". They don't exchange single components, only entire cards. So, is there anyone out there who knows where to find components of the right type?
ANSWER 1: There's a good chance that all that's needed to repair your SE analog board is a good resoldering of the back of the J1/P1 connector. Otherwise, you can get replacement Mac parts from many suppliers

ANSWER 2: According to Larry Pina in The Dead Mac Scrolls, the most common component failure that causes your symptom is capacitor C15 on the analog board. If possible, replace with a 3.9 uF 100 Volt High-Frequency part. Also, check the yoke plug P1, it may be burned. In the US, Mouser Electronics sells a 3.3 uF 50 V HF capacitor for under a dollar in single quantities. Worked for me.

ANSWER 3: The exact capacitance isn't critical (I'm not surprised to see a 3.3 uF cap work properly in place of the original 3.9), but make sure you use a non-polar capacitor as a replacement. Most electrolytic capacitors are polar, and will die rapidly if you use them here. Other components to check: R19 - if burned, replace. Also completely de-solder and then re-solder coil L3 with fresh solder. Also, check tunable coil L2.


QUESTION:

Where is the analogue board? Sitting on the back of the yoke?
ANSWER: No, that would be the vertical board. The analog board is the large circuit board on the left side (looking at the SE from the front) that controls most of the functions of the monitor. It is called the analog board to distinguish it from the (digital) logic board, or motherboard, at the bottom of the case.