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California Computers S100 smurf grenades me

falter

falter

Veteran Member
Joined
Jan 22, 2011
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Location
Vancouver, BC
Bought this CC chassis because it was local and looked to be in immaculate, possibly even unused condition, and indeed it was near perfect.. unless a tantalum explosion.

I brought it up carefully with the variac, everything seemed okay, but once I hit full power, one of the little b---rds let go. Man, for a small device, they sure do some damage. Left its guts on the s100 slot and sprayed buckshot into the paint on the lid above. Glad I had it closed! It kind of scares me how many vintage machines I have with these little bombs sitting in there, waiting. Think I'm going to just assume they're bad now and replace them all on whichever machine I'm working with. They give you quite the start when they go off!

I'm going to assume it's just a bad cap.. none of the others went bang.

Guess I'd better get back to my power supply lessons!
 

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I appreciate the effort the layout engineer went to here in order to provide a nice cluster bomb. I've seen fireworks shows with worse coordination.
 
Yeah the blue drop tantalums are all more or less unstable now. They may be fine on one power cycle but they can and will spontaneously become a dead short.
 
NeXT said:
Yeah the blue drop tantalums are all more or less unstable now. They may be fine on one power cycle but they can and will spontaneously become a dead short.
Click to expand...
I have a Sol 20 that is full of them. I was warned about these but never thought much of it as the machine was repeatedly powered up and used without incident. But now...
 
Hugo Holden said:
All of the blue tants require replacing at this point. The others will soon follow.
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I always wonder, do the huge electrolytics make decent explosions? I had a small one blow up inches from my face... but it just made a puff of air. It was rather underwhelming.
 
seat safety switch said:
I appreciate the effort the layout engineer went to here in order to provide a nice cluster bomb. I've seen fireworks shows with worse coordination.
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I consider myself lucky they didn't start a chain reaction. I'd have a hard time explaining the crater where my desk used to be.
 
I wonder if CC sold chassis by themselves. I really don't think anything has ever been installed in this one.

I have a pile of S100 boards I'd love to use but have been fearful of blowing them up. I thought I might build a new S100 chassis but don't trust my skills. So then this came up a few miles from me and I thought perfect! But instead I just got another project.
 
falter said:
I always wonder, do the huge electrolytics make decent explosions? I had a small one blow up inches from my face... but it just made a puff of air. It was rather underwhelming.
Click to expand...
Yes, 3100uF @450V units fail quite energetically. This sample put chunks of the thick top through the suspended ceiling in the lab. Our setup had ~3000 of them in a large array. Sub assembly photo for scale.

IMG_2221.jpeg
 
I wonder, if in the cast of tant's on a backpanel/motherboard, it might be wise to mask off connectors and other parts, with Kapton tape first. Then maybe just 'shock' them with a full power right off the bat. If one, or more, are close to failure, that may get rid of the one's on the edge; whereas a slow power on, might 'cover' for them, until you have everything all put together... Then 'ka-bam'....

YouTube video of blowing up capacitors:
 
We had a large electrolytic 'go' when I was at school. I was a member of the electronics club and we were repairing an old ex war department oscilloscope at the time.

Fortunately, very large electrolytic capacitors have a vent plug that goes before the capacitor explodes. The vent plug bursts when the pressure reaches a certain level.

Of course, it still lets out the magic, smelly smoke that lingers...

After that (and another unrelated event) it was decided that repairing ex war department equipment was too dangerous - but the learning that has lasted is to have a healthy respect for electronics and to think through the potential consequences of my actions before I undertake a piece of work and mitigate against them (as far as possible)...

Dave
 
Amazing how many people don't recap machines during the restoration process.
In the vintage radio realm, all caps are replaced. Doesn't matter if it works or not.
It was explained to me by analogy:
Not replacing them is like finding a classic car in a dry barn in Kansas.
And then driving it without replacing the oil.

A 'proper' maintenance schedule takes component lifetimes into account, and replaces them when the time limit approaches - before the part actually fails.
But, alas, this is a hobby, and not a serious engineering endeavor.
...and capacitor explosions are really cool... 🤓
-J
 
I read differing advice on replacing caps. There are people who say you must replace every cap right away, and others who say it's unnecessary and can lead to other damage due to the repair process. I've fired up my Sol 20 dozens of times with blue smurf grenade pins pulled, running for hours at a time sometimes, and no issue. Machines like that, I'm really reluctant to take apart due to their fragility and the challenge of doing the repair in a way that doesn't cause more damage.

Once I have this CC chassis repaired... what would be the recommended procedure for testing it with actual S100 boards? Do I have to worry at all about compatibility? S100/Altair bus is same regardless, right?
 
>>> S100/Altair bus is same regardless, right?

Wrong...

Various manufacturers had their own ideas about the S-100 bus. Meaning that most things will work together, some things may not work as planned, and other times you will have plain trouble.

For example, Cromemco have bank switching memory to extend the memory space available to various operating systems. If you stick with 64K and CP/M you will rarely run into trouble.

The Cromemco Dazzler graphics card is VERY particular about the memory card it works with. If you are not using a Dazzler, that is not a problem.

If you want a front panel (blinking lights etc.) this is where some of the problems start.

Some of the S-100 pins have changed function over time. Not many of them, but the odd one. I seem to remember some combinations of boards requiring you to put insulating tape over one pin of a card.

You must do your homework...

But, in general, if you stick with the simple things, you should be fine.

Sticking with one manufacturer for the cards should simplify things.

Dave
 
falter said:
Once I have this CC chassis repaired... what would be the recommended procedure for testing it with actual S100 boards? Do I have to worry at all about compatibility? S100/Altair bus is same regardless, right?
Click to expand...

It's unlikely you'll run into compatibility problems with the backplane, it really is just a dumb array of wires. Compatibility glitches in between cards is a whole other kettle of fish. It's not likely you'll damage anything, but the general rule with S-100 is it wasn't ever really *completely* standardized until very late (The IEEE-696 standard was drafted in 1979 but wasn't approved until 1983) and the "standard" that finally emerged redefined major aspects of the bus compared to the original Altair version. Cards were encouraged to be backwards compatible, but being completely so is usually unrealistic.

The SOL-20 was actually one of the notable early examples of an incompatible machine because it doesn't implement a completely separate pair of mono-directional data busses, it ties them together. (The 696 standard takes this incompatibility further by following the SOL's example of moving to bidirectional data busses and repurposing the "redundant" half into a 16 bit extension.)

Again, you probably won't roast anything if you just shove random cards into a chassis, but making them all work together means RTFM-ing, and some combinations just won't work. (Compatibility with switch front panels was one of the first things to go, FWIW.)
 
Yes sorry, I should have been clearer. I did not expect random S100 cards to operate well together. I just was concerned about changes to things like power pins. I don't want to plug in a card and have it go 3 Mile Island. I will of course read extensively before even thinking about plugging one in, but as I am not an EE I don't always have 100% confidence that I have read things right.
 
Power is fairly standard. The beauty (and annoyance) of an S-100 system is that unregulated voltages are on the S-100 bus (which simplifies the main power supplies) at the expense of each S-100 card carrying their own voltage regulators.

Just make sure you install the cards the correct way round!

Dave
 
… re the power pins, there were a few system integrators (and probably some individuals) that built custom systems where they bypassed the regulators on every card and replaced the unregulated 8/18v lines with 5/12v power from a more modern switching power supply. If you have any cards in your possession that *don’t* have the giveaway big TO cans and heatsinks on them you might want to post pictures of them before you mix them into a normal S-100 system… but this is a pretty rare edge case.
 
So let's say you have a Northstar Horizon or Poly 8813 like I do that you've never powered up.. what would be the procedure you would follow to minimize the risk of kaboom? Is it simply:

1) Replace all caps (especially tantalum)
2) Bring up empty chassis on Variac slowly
3) Check cards for obvious shorts, plug in and bring up slowly?

I'd really love to get these going but am just convinced they'll light up.
 
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