Mac Plus--good interior, and has had C1 replaced

[Apostrophe]

Hi,

Just opened my Macintosh Plus to give it a quick check-over, to make sure that no components have blatantly malfunctioned. Generally, it looks okay on the interior:

There is a bit of oxidation on the metal chassis, as visible here. Luckily, no components seem to be affected.

And capacitor C1 (the Capacitor That Often Dies) has been replaced some time in the past:

So I won't run into problems on the C1 front for a while.

What does a C1 failure result in, anyway?

-Apostrophe

 

[4seasonphoto]

Oxidation, nothing, that's corrosion, and it looks like something got spilled on the board.

How can you tell that C1 has been replaced? Looks to me like the original factory hot glue is undisturbed. You may simply have a later revision of the analog board which incorporates improvements.

 

[Charlieman]

Should we hot glue replacement components? Capacitors vibrate but does the glue make any difference to life span?

 

[tomlee59]

Using hot glue is advised if the computer is going to experience a lot of vibration. In an ordinary home desktop environment, it's unlikely that you'll need to use glue. I have a feeling that the designers were primarily concerned with protecting the components during shipping.

As to C1: Its failure results in a lack of horizontal deflection (so that you only see a vertical line down the middle of the screen), or weak deflection. These abnormal conditions can also have the secondary effect of causing the high-voltage circuitry to misbehave. Symptoms can range from a dim display to a completely dark one. And, on occasion, banshee-like screeching noises from the HV (flyback) transformer, followed by emission of the all-important magic smoke.

 

[Osgeld]

really the main point of hot glue is to hold the larger / top heavy components in place as they scurry down a convener belt during assembly

Secondary it provides a little bit of protection against shock and vibration

 

[JDW]

That C1 is the same exact C1 cap used in some of my newer "stock condition" analog boards, all with factory hot-glue applied:

630-0102-E







661-0462




And here is an unmodified analog board that shipped with the Mac 128k, dated 1983, with an older version C1 and no hot glue (but unlike some other early Mac 128k analog boards, this C1 is non-polarized, high-frequency, and rated at 100V -- a cap selection not prone to failure like the inferior polarized 25~35V rated C1 caps):

630-0102













If you do ever wish to swap out C1, "Metallized Polypropylene" is a replacement that will probably outlive you:

http://spreadsheets.google.com/ccc?key=0AnmQLg8d1xThcE96S1Z0S3oxOUFiMkJEYy1nNzNuZEE&hl=en

With regard to caps and hot glue, my company typically applies hot glue to electrolytic caps that are more than 1.5cm in height, especially on some of our truck alarms that will be used in environments with above average vibration. And while there is no vibration in the Mac 128k or 512k or Plus, Apple clearly found it important to apply hot glue on the tall caps on latter analog boards (noting once again that the oldest analog boards did not have the hot glue). It could have been due to Apple having later conducted vibration tests at the factory to simulate the jolts products would receive during shipping/handling. The hot glue is there to keep the two leads from the cap from breaking or otherwise detaching from the cap body.

 

[Apostrophe]

Oh, okay. Guess I was wrong about the C1 being replaced. Since it didn't look like the other capacitors, I just assumed it was a replacement made by some other company...oh well.

ASAP I'll try to get some sort of corrosion/oxidation-removing chemical for the Plus's power socket and the chassis.

Thanks for the clarification JDW,

-Apostrophe