Are bad ramchips common?

[Keatah]

I recently came across 4 Apple //e consoles. All of them had bad ram chips of some sort or other. Failed diagnostics and garbage on screen. Or something like that.

Is this unusual? OR do you think that that ram chips of that era are not as durable as the other standard logic gates?

I recall, back in the day, also having to replace a ram chip in my II+ and again in my //e. And now these 4 systems.. yikes!

 

[Geo3]

Usually no, but a bad batch could have gotten out there. There was that problem with the IIgs. Cas before Ras that caused problems.

 

[Keatah]

Possibly. These //e consoles were gotten from a variety of disparate sources and don't have chronologically close serial numbers. But it seems the address lines are shorted or weak. No solid logic 0/1 operation. Very sloppy.

 

[RetroHacker_]

Bad RAM chips are much more common in II+'s, simply because the three-voltage 4116's are inherently kind of unreliable. They run hot, and over time, tend to have a fairly high failure rate. With a bit of pin-bending and soldering, you can use a 4164 to replace a 4116 if you don't have one handy. 4116's are a very common failure in video games too, and it's actually rather common (with a simple trace cut and board mod) to replace all the 4116's in a game like Defender with 4164's, because they run cooler and don't draw as much power.

IIe's use 4164's, and while they are much more reliable than the 4116's, they do still fail. I've replaced several. The worst seem to be the older gold topped RAM chips. Most 4164's are plastic, but on the occasion I've found machines with the gold ones, they usually have at least one faulty.

So, while it's highly unusual that you would have four machines in a row with bad RAM, it's not unheard of.

-Ian

 

[Keatah]

It's these 4 units and my own "personal" //e I owned since the early 1980's. And these are MT. The one thing I noted in common was all the failed chips had the Apple logo stamped on them. The other ones like from OKI, or TI, or NEC or Fairchild, and so on and so forth, never failed.

II+ rams reliable? HA, I replaced many of them back in the day. And most had the Apple Logo going as well! Now that I recall..

Well, 4164's are plentiful enough, at least in my junk box so everything is good.

Strange. But whatever. Perhaps some special radiation oozing out of the ground that targets these chips specifically or something..?