10 May
2016
10 May
'16
3:39 p.m.
My father is a civil engineer. When I was a little
kid, he was in the US Air Force. We would frequently
go to the runway snack bar, get ice cream and watch
the B-52s do "touch-and-go" landing practice. The
plane's wings would "flap". It raised the hair on
the back of my neck. My dad explained that, if they
didn't flex, the wings would break off. After a
while, I understood, intellectually. It still "gave
me the willies". Later I had a similar experience
when I was with him in a tall building and realized
that it was "waving in the wind". Same thing, if it
didn't flex, it would fall.
That reminds me of the following joke :
There is an airline passenger. During some particularly
turbulent conditions he looks out the window and sees
the plane's wings flexing. He looks very worried.
The flight attendant comes over to him and tries to
comfort him by saying
'Our pilots are fully trained to fly in conditions like
this. It's only turbulence, it's quite normal'
He replies
'You don't undertand. I work for Boeing. I am one
of the men who designed this aircraft. The wings
are not supposed to flex like that.'
The other is
that, as I said before, any ground
connection has impedance (it's the inductance that
is troublesome normally) so that points (say IC pins)
that are shown as grounded may actually have a
voltage difference between them.
If I think about it too much, this gives me the
willies, the same way. 
10 May
10 May
4:03 p.m.
On Tue, 10 May 2016, tony duell wrote:
It's a very real problem, it's the main reason
for decoupling capacitors
which provide a local source of power with a low impedance connection
(as they are so close to the IC).
It seems like there is a lot of "fiddling" with those types issues and
getting good at doing so is part of the process of getting profecient with
component level troubleshooting. That's why working with electronics
"kits" (ie.. kit based projects) is about my speed right now. In most of
those cases, folks have worked out the kinks involving connection issues,
but I'm still just doing analog stuff. I have no idea how much it'll
matter when I go to learn a bit about digital. However, that quote about
digital circuits being made from analog physical bits seems like good
foreshadowing. So, we'll see.
I'm still playing along with projects from a kids' Elenco kit. I'm having
fun with timers and making "bleeps and bloops". I'm also using it to try
and figure out how about 5% of my borrowed ocilliscope works. I've got the
manual, it's just figuring out what everything means is a bit challenging
right now. So, it helps teach me how to calibrate the darn thing to just
sit on something that looks like a sine wave etc...
-Swift
6:09 p.m.
In order to trouble shoot, one needs to know how it is suppose
to work. This often means studying schematics, data sheets and
sometimes even app-notes.
Avoid the replacing everything, until it starts working, type trouble
shooting. As well as being a waste of time, it is more likely that
you will introduce new problems in the process.
Don't replace a part unless you can prove it to yourself that it is
the most likely source of the error. This usually means running
experiments. Since you are a coder, I find that anything with a working
processor can be used as a self debugging tool. EPROMs or
front panels are great for trouble shooting. Simple test are best.
Many fear power supplies. Linears are the easiest because they
are always some form of feedback loop. You just follow the loop
until you find two points that are opposite directions from where the
input point predicts the output point should be( goes back to knowing how
it should work).
If you can't find a schematic on the web, draw one. As a minimum, have
a block diagram.
I'm sure you have heard of the "scientific method". Trouble shooting is
just that. It is the repetitive process of making an educated guess as
to the source of the problem and then having an experiment to
prove it either true or false. Try to have experiments that are conclusive.
This is why I don't much care for the piggy back RAM test.
It may or may not tell you that there is a problem with the RAM that
you are checking.
Learn to use a two channel oscilloscope with trigger and delayed
sweep.
Dwight
________________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Swift Griggs
<swiftgriggs at gmail.com>
Sent: Tuesday, May 10, 2016 1:03:44 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: "Retro Repair" key electronics skills?
On Tue, 10 May 2016, tony duell wrote:
It's a very real problem, it's the main reason
for decoupling capacitors
which provide a local source of power with a low impedance connection
(as they are so close to the IC).
It seems like there is a lot of "fiddling" with those types issues and
getting good at doing so is part of the process of getting profecient with
component level troubleshooting. That's why working with electronics
"kits" (ie.. kit based projects) is about my speed right now. In most of
those cases, folks have worked out the kinks involving connection issues,
but I'm still just doing analog stuff. I have no idea how much it'll
matter when I go to learn a bit about digital. However, that quote about
digital circuits being made from analog physical bits seems like good
foreshadowing. So, we'll see.
I'm still playing along with projects from a kids' Elenco kit. I'm having
fun with timers and making "bleeps and bloops". I'm also using it to try
and figure out how about 5% of my borrowed ocilliscope works. I've got the
manual, it's just figuring out what everything means is a bit challenging
right now. So, it helps teach me how to calibrate the darn thing to just
sit on something that looks like a sine wave etc...
-Swift
6:43 p.m.
On Tue, 10 May 2016, dwight wrote:
In order to trouble shoot, one needs to know how it is
suppose to work.
This often means studying schematics, data sheets and sometimes even
app-notes.
Cool. I'm good on this. I love schematics when I can get them. I can't
always figure out what I'm looking at but it sure helps vs looking at a
board!
Avoid the replacing everything, until it starts
working, type trouble
shooting. As well as being a waste of time, it is more likely that you
will introduce new problems in the process. Don't replace a part unless
you can prove it to yourself that it is the most likely source of the
error.
This strikes me as very good advice. I use the same type of mentality when
I troubleshoot computer components and servers. I'm sure it's just as
sound when dealing with components.
This usually means running experiments. Since you are
a coder, I
find that anything with a working processor can be used as a self
debugging tool.
I love that phrase "Self debugging tool."
EPROMs or front panels are great for trouble shooting.
Simple test are
best.
I'm a Unix guy. Simple is almost always better. :-)
Many fear power supplies. Linears are the easiest
because they are
always some form of feedback loop. You just follow the loop until you
find two points that are opposite directions from where the input point
predicts the output point should be( goes back to knowing how it should
work).
Okay, I'm one of those with a little fear of power supplies. It's little
because I'm still ignorant (*grin*). Funny you should mention power, I'm
studying this section on DC metering to build up to learning more about
power circuits:
http://www.allaboutcircuits.com/textbook/direct-current/chpt-8/what-is-a-me…
BTW, I'm growing pretty fond of this instruction on allaboutcircuits. They
have some really great material with excellent explanations & drawings.
If you can't find a schematic on the web, draw
one. As a minimum,
have a block diagram.
I keep reading that. I'm taking it to heart, mainly because I can barely
keep up with one part of a circuit before having to move on and figure out
a different part. Writing it down is the only way I could do it anyway. :)
I'm sure you have heard of the "scientific
method". Trouble shooting is
just that. It is the repetitive process of making an educated guess as
to the source of the problem and then having an experiment to prove it
either true or false. Try to have experiments that are conclusive.
That's good advice, in general, I think. I try to do the same with any
type of troubleshooting. Even the Monte Carlo method (which I think rocks)
is usually framed as an controlled experiment.
Learn to use a two channel oscilloscope with trigger
and delayed sweep.
Great! I've been looking into that. I'm guessing that helps when you are
trying to look at a detailed edge/level and you can overlay the two wave
forms? Also do you use variable holdoff much in real life? I'm reading
about how it works, and it sounds useful in theory (and if I buy a scope,
it *sounds* good). However, at my level, I'm not sure I'd ever use it. It
just keeps coming up a lot when reading about scopes.
-Swift
5:25 p.m.
New subject: News about hpmuseum.net
The following was posted on hpmuseum.org this morning:
*RE: Jon Johnston Passes *
As an update to the sad news of Jon Johnston's death, I can advise that
the HP museum and the hpmuseum.net website he built will be continued
and maintained for the foreseeable future.
Over the last 8 months I have worked with Jon in restoring items from
his collection of equipment and, among a range of items, recently
restored an HP2116A computer to working order - one of only two Jon was
aware of in the world and the only one that's operational.
At this stage we have not been able to access the website and put any
notices or updates but that should be addressed shortly.
Jon's wife has asked me to look after the museum and website for the
foreseeable future and as much as possible, continue to develop the
museum in line with Jon's vision and objectives.
As a short background, I joined HP Australia in 1982 as a Customer
Engineer maintaining HP3000s, HP250s, all peripherals, terminals etc. I
stayed with HP for over 26 years (including 5 years in Palo Alto) in a
range of Services roles and have many fond memories of the company and
the people I worked with.
While my ability to invest time into the museum is more limited than
Jon's, I hope to honour both his memory and the legacy of the 'old HP'
by keeping the museum going as best I can, hopefully with help from the
HP interest groups across the world.
David Collins
12 May
12 May
2:50 a.m.
New subject: News about hpmuseum.net
This is great news despite the sorrow. Thank you for that, the museum is such an awesome
resource for HP collectors. I saw your video on the 2116 restoration were both Jon and you
appear. We have at least one more at the CHM, just as a static display for now. I hope I
can visit you in Melbourne one day.
Marc
Sent from my iPad
On May 10, 2016, at 2:25 PM, Paul Berger <phb.hfx
at gmail.com> wrote:
The following was posted on hpmuseum.org this morning:
*RE: Jon Johnston Passes *
As an update to the sad news of Jon Johnston's death, I can advise that the HP museum
and the hpmuseum.net website he built will be continued and maintained for the foreseeable
future.
Over the last 8 months I have worked with Jon in restoring items from his collection of
equipment and, among a range of items, recently restored an HP2116A computer to working
order - one of only two Jon was aware of in the world and the only one that's
operational.
At this stage we have not been able to access the website and put any notices or updates
but that should be addressed shortly.
Jon's wife has asked me to look after the museum and website for the foreseeable
future and as much as possible, continue to develop the museum in line with Jon's
vision and objectives.
As a short background, I joined HP Australia in 1982 as a Customer Engineer maintaining
HP3000s, HP250s, all peripherals, terminals etc. I stayed with HP for over 26 years
(including 5 years in Palo Alto) in a range of Services roles and have many fond memories
of the company and the people I worked with.
While my ability to invest time into the museum is more limited than Jon's, I hope to
honour both his memory and the legacy of the 'old HP' by keeping the museum going
as best I can, hopefully with help from the HP interest groups across the world.
David Collins
11:21 a.m.
New subject: News about hpmuseum.net
Thanks Marc, much appreciated. Happy to host you if you ever make if down
this way.
David Collins
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of
curiousmarc3 at gmail.com
Sent: Thursday, 12 May 2016 4:50 PM
To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Cc: Verdiell Marc <marc.verdiell at gmail.com>
Subject: Re: News about hpmuseum.net
This is great news despite the sorrow. Thank you for that, the museum is
such an awesome resource for HP collectors. I saw your video on the 2116
restoration were both Jon and you appear. We have at least one more at the
CHM, just as a static display for now. I hope I can visit you in Melbourne
one day.
Marc
Sent from my iPad
On May 10, 2016, at 2:25 PM, Paul Berger <phb.hfx
at gmail.com> wrote:
The following was posted on hpmuseum.org this morning:
*RE: Jon Johnston Passes *
As an update to the sad news of Jon Johnston's death, I can advise that
the HP
museum and the hpmuseum.net website he built will be continued and
maintained for the foreseeable future.
Over the last 8 months I have worked with Jon in restoring items from his
collection of equipment and, among a range of items, recently restored an
HP2116A computer to working order - one of only two Jon was aware of in the
world and the only one that's operational.
At this stage we have not been able to access the website and put any
notices or
updates but that should be addressed shortly.
Jon's wife has asked me to look after the museum and website for the
foreseeable future and as much as possible, continue to develop the museum
in line with Jon's vision and objectives.
As a short background, I joined HP Australia in 1982 as a Customer
Engineer
maintaining HP3000s, HP250s, all peripherals, terminals etc. I
stayed with HP for over 26 years (including 5 years in Palo Alto) in a range
of Services roles and have many fond memories of the company and the people
I worked with.
While my ability to invest time into the museum is more limited than
Jon's, I
hope to honour both his memory and the legacy of the 'old HP' by
keeping the museum going as best I can, hopefully with help from the HP
interest groups across the world.
David Collins
3027
days inactive
3029
days old
6 comments
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participants (6)
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