Invisible wrote:
> ...  although I also found ... a small bottle of white powder marked
> "KNO3"...

A little charcoal and sulfur and *you* *are* *in* *business* *!*

> Some capacitors are small brown things like little chocolate buttons. 
> (But significantly less tasty.) Then there's the "electrolytic" ones, 
> which are small blue things that look like they belong in a licorish 
> all-sorts bag. Some a really small (about 5mm diammeter). Some are a bit 
> bigger (15 mm diammeter).
> 
> When I was in my dad's loft, I found capacitors the size of friggin' 
> soda cans! o_O WTF are *those* for??
> 
> (I mean, are they that size because they have a higher capacitance or 
> something? I gather a capacitor is one of the few components where the 
> physical size of the device determines its electronic characteristics...)

A capacitor consists of a piece of electrolytic material sandwiched 
between two conducting plates.  The capacitance is proportional to the 
area of the plates, is inversely proportional to the distance between 
the plates, and is factored by the capacitance of the electrolytic 
material between the plates.  To get up to where capacitance is measures 
in farads (instead of microfarads), you need large plates, the thinnest 
possible spacing between them, and the best material to go between (as 
to which material is the best, I am not in the know).  The most reliable 
manufacturing technique is to take a thin layer of flexible electrolyte, 
  plate it with metal on both sides, insulate one of the two sides, and 
roll the plates up so that they take less room.

If they're old components, it may be that manufacturing techniques 
didn't allow the two plates of the cap to be closer together.  To make 
up for a lack of precision, you have to increase the area of the plates. 
  It all comes down to how thin the electrolyte can be and still 
physically separate the two plates (because if the plates make 
electrical contact, the cap becomes a wire).

> We also found a box containing more 14-pin DIL sockets then it is 
> humanly normal to have. And a bunch of 7400-series chips. In particular, 
> these are the original, obsolete, 7400 chips. 7400, 7408, 7402, etc. Not 
> 74LS00 or even 74S00, but vanilla 7400 TTL. They're that old.
> 
> We also found a stack of unopened boxes containing LEDs. Now when I was 
> at Maplin I bought a bag of mixed LEDs - which is great, because you get 
> a lot of LEDs for not much money, but OTOH they're all different. Now I 
> have a matching set!

Good.  Now you should be able to build a small, functioning processor. 
With pretty lights to show the data states.

Regards,
John

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>> ...  although I also found ... a small bottle of white powder marked
>> "KNO3"...
> 
> A little charcoal and sulfur and *you* *are* *in* *business* *!*

And why did you *think* my dad had this? ;-)

>> We also found a box containing more 14-pin DIL sockets then it is 
>> humanly normal to have. And a bunch of 7400-series chips. In 
>> particular, these are the original, obsolete, 7400 chips. 7400, 7408, 
>> 7402, etc. Not 74LS00 or even 74S00, but vanilla 7400 TTL. They're 
>> that old.
>>
>> We also found a stack of unopened boxes containing LEDs. Now when I 
>> was at Maplin I bought a bag of mixed LEDs - which is great, because 
>> you get a lot of LEDs for not much money, but OTOH they're all 
>> different. Now I have a matching set!
> 
> Good.  Now you should be able to build a small, functioning processor. 
> With pretty lights to show the data states.

Negative.

I tried to solder the LEDs to a board, but for reasons beyond my 
comprehension, there's a short-circuit somewhere. I've checks and 
re-checked the board. I can't see the short. But there is one.

I think I need to go buy some solder that isn't 30 years old...

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On 6/7/2010 9:11 AM, Invisible wrote:

>
> I tried to solder the LEDs to a board, but for reasons beyond my
> comprehension, there's a short-circuit somewhere. I've checks and
> re-checked the board. I can't see the short. But there is one.

You know... a $15 multimeter with a continuity tester ....

Heh. I proudly proclaimed to my dad that I just repaired my USB 
thumbdrive's connector all by myself.

His first response was "Does it still work?"

It does! Hehe.


-- 
~Mike

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>> I tried to solder the LEDs to a board, but for reasons beyond my
>> comprehension, there's a short-circuit somewhere. I've checks and
>> re-checked the board. I can't see the short. But there is one.
> 
> You know... a $15 multimeter with a continuity tester ....

I have one. That's how I know there's a short circuit. I just can't 
figure out *why*.

When I was soldering one of the components, the solder spilt onto the 
adjacent track. I've tried to fix at a dozen times now, but I'm still 
getting continuity somehow...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On 6/7/2010 1:56 PM, Orchid XP v8 wrote:

>
> When I was soldering one of the components, the solder spilt onto the
> adjacent track. I've tried to fix at a dozen times now, but I'm still
> getting continuity somehow...
>

Do you have some copper braid or a solder pump? that should clean it off.

-- 
~Mike

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>> When I was soldering one of the components, the solder spilt onto the
>> adjacent track. I've tried to fix at a dozen times now, but I'm still
>> getting continuity somehow...
>>
> 
> Do you have some copper braid or a solder pump? that should clean it off.

There was a blob of solder between the tracks. So, as per the 
instructions in my trusty old electronics book, I ran the point of the 
iron down the groove between the tracks.

In three cases, this fixed the problem. In the forth case, a short 
circuit still exists somehow.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On 07/06/2010 7:51 PM, Mike Raiford wrote:
> On 6/7/2010 9:11 AM, Invisible wrote:
>
>>
>> I tried to solder the LEDs to a board, but for reasons beyond my
>> comprehension, there's a short-circuit somewhere. I've checks and
>> re-checked the board. I can't see the short. But there is one.
>
> You know... a $15 multimeter with a continuity tester ....
>

Or eyes for solder blobs,

> Heh. I proudly proclaimed to my dad that I just repaired my USB
> thumbdrive's connector all by myself.
>
> His first response was "Does it still work?"
>
> It does! Hehe.
>
>

:-D

-- 

Best Regards,
	Stephen

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On 07/06/2010 8:02 PM, Orchid XP v8 wrote:
>>> When I was soldering one of the components, the solder spilt onto the
>>> adjacent track. I've tried to fix at a dozen times now, but I'm still
>>> getting continuity somehow...
>>>
>>
>> Do you have some copper braid or a solder pump? that should clean it off.
>
> There was a blob of solder between the tracks. So, as per the
> instructions in my trusty old electronics book, I ran the point of the
> iron down the groove between the tracks.
>
> In three cases, this fixed the problem. In the forth case, a short
> circuit still exists somehow.
>

A sharp knife or a scalpel works wonders.
You need the right tools to do the job.

-- 

Best Regards,
	Stephen

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Stephen wrote:

> You need the right tools to do the job.

Hence my suggestion that I should buy some solder that isn't 30 years 
old. (I suspect my iron also needs a new tip...)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On 07/06/2010 8:17 PM, Orchid XP v8 wrote:
> Stephen wrote:
>
>> You need the right tools to do the job.
>
> Hence my suggestion that I should buy some solder that isn't 30 years
> old. (I suspect my iron also needs a new tip...)
>

You can file it, then tin it. But new tips are a good idea.

-- 

Best Regards,
	Stephen

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