[Coco] CoCo2 PAL version service manual

[Gene Heskett]

On Thursday, January 08, 2015 07:16:34 AM Daniel Campos did opine
And Gene did reply:
> 2015-01-08 10:14 GMT-02:00 Cocodemus <retrocanada76 at gmail.com>:
> > Daniel, its time for you to buy a scope :P
> 
> First things first. :-P
> 
> Daniel

Daniel, having a scope probe or a hot soldering iron in one hand since I 
was 16, 64 years ago, a decent scope that reads DC voltages too, would be 
the first or second purchase if I did not already have 2 of them, one 
analog 100 MHz dual trace, and just recently bought a digital version 
thats 10x smarter than my computer boosted Hitachi, and at $400 cost 
1/3rd what the used Hitachi cost 25 years ago.

The scope is as close to a universal measuring tool that has ever been 
built. It is not a toy, nor even a nice to have, it is a prerequisite to 
being able to wander through a circuit to determine if its working right, 
or was even designed by someone who knew what he was doing.

I have been surprised at the design mistakes I have found although I 
can't say that about the coco except for its puny power supply and chip 
select decoding. Not carrying that function out to the logical equ of a 
/4, but stopping at a /$20 should have been a prosecutable crime.  One 
you've read my tirades about several times previously if you've been on 
this list since the Chestnut and Princeton days.

The temperature controlled soldering iron would be the other choice, but 
I already own a couple of those too.

The third item on the list is a decent capacitor checker that can measure 
ESR in circuit.  But I can take a function generator and the scope and 
imitate it well enough with a calculator in most cases. Simple ohms law 
for AC principles.

And if the function generators square wave output has fast enough edges, 
not often the case, the one I have now doesn't, I can use it and the 
scope as a time domain reflectometer, telling me where, in 2000 feet of 
transmission line that a burnout has occurred, so I can tell the tower 
climbers how far up the tower they go before starting to take it apart 
for rebuilding.

The 4th thing would be a analog multimeter, except whats made today are 
$15 toys from China.  Digital has taken over, but the analog toy still 
has its place as it will see, and wiggle the needle, stuff the the usual 
dual integrator digital version ignores. Pocket sized, load the circuit 
very heavily, but it tells you when to go get the much larger scope and 
find out whats actually going on. And probably just as made in China.  So 
I have a couple of those digital ones too.

But the scope is first, because without it, you are so blind that the 
soldering iron might as well be left unplugged.

Please don't take this as a rant Daniel, but as friendly advice from 
someone who really has been there and done a lot of "that". Nearly 70 
years worth of BTDT. Tested and passed for certificates (A C.E.T.) and 
licenses (FCC 1st Phone) along the way. Bought a few T-Shirts along the 
way too. ;-)

Retired for a decade and change now, I am pleased that we have some up 
and coming, curious people to keep up the good work when I am gone, as I 
will eventually do. People who are "making things happen" here on this 
list, you KNOW who you are, and I thank you for keeping the dream alive 
as the technology advances by taking advantage of that technology for 
affordable enhancements to the coco.

But I still have a rather lengthy bucket list too, not all of which 
involves our beloved coco.

Stuff like my cnc machines, woodworking and guns, that keeps me out of 
the bars don'tcha know. ATM I am doing the coding and prep work to carve, 
from Gabon Ebony, the blackest wood you can buy, at least 36 good, square 
with rounded corners, .440" hole plugs, and a dozen .500" of the same, 
for a blanket chest made in the Green & Green style from 100 years ago, 
as shown in the fall 2014 issue of Fine WoodWorking Magazine. The ebony 
is costly so I'm making test fit runs from oak, which I have lots of. I 
will have around $700 in it when I am done, but could make a second one 
for about $450.  And much much faster since the gcode to cut the joinery 
on the cnc mill has already been written. Am I doing it faster than a 
master craftsman could do it? Don't know, but it takes my milling machine 
around 15 minutes to cut out 3 of them, so once I get started, and 
allowing 5 minutes to reset the ebony in the jig to make 3 more, I'll 
have 4 hours in the 36 of the smaller size. But it was -0.4F when I got 
up this morning and still only 3F now, and my shop is not at all well 
insulated so my diabetic feet limit my "at a time" time doing this.

Cheers Daniel, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
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-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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