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EEVblog #648 - Mailbag
Posted by
EEVblog
on 03 Aug, 2014 23:19
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#1 Reply
Posted by
221-b
on 04 Aug, 2014 00:32
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Dave,
The Swiss Army Knife made me itch but the new "broadsword" was hilarious!
I am poor enough at electronics that my wife has to change all the batteries but I think I noticed a hole damaging one or two conductors of the bodged flat flex in your internet radio. It was a couple inches from the tear "repair". You have probably caught it already but just in case... Many thanks for all the shockingly good video!
Brian
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#3 Reply
Posted by
max666
on 04 Aug, 2014 00:59
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That magnetic memory is fascinating, would love to see you write and read some stuff on it, Dave.
Jeri has done a nice vid on Magnetic Logic:
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#4 Reply
Posted by
Vgkid
on 04 Aug, 2014 02:09
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This is a really neat mailbag Monday, gotta love the Magnetic Core memory.
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#5 Reply
Posted by
BravoV
on 04 Aug, 2014 02:28
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Lol ... love that knife Dave !
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#6 Reply
Posted by
robbak
on 04 Aug, 2014 03:00
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Make sure that, before you write to that core, that you do a full read! Although core memory is destructive read (you basically set the bit back to zero and measure whether you get a voltage spike that tells you it changed), it is otherwise non-volitaile, so that core will have decades-old data sitting on it.
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#7 Reply
Posted by
EEVblog
on 04 Aug, 2014 03:13
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it is otherwise non-volitaile, so that core will have decades-old data sitting on it.
all 400 words of it
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#8 Reply
Posted by
pickle9000
on 04 Aug, 2014 03:21
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If it has "Nixon sucks" or "Dickhead" on it then it will all be worth it.
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#9 Reply
Posted by
NiHaoMike
on 04 Aug, 2014 03:26
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On the radio, it looks like there's a hole in the cable a little up from the connector. Should be easily fixable if the pitch isn't too small. I'm also surprised they used an old audio amplifier design that needs a heatsink, especially on something that can be battery operated. A modern amplifier of that power level would be a little SMD chip on the board.
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#10 Reply
Posted by
Stonent
on 04 Aug, 2014 03:57
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I've wondered if 3M Z Axis tape could be used to splice flat flex cable?
I'm sure David L. "Crocodile Clip" Jones could come up with something better, though.
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Thanks for selecting my package and taking that Chinese DMM apart
My 9-year-old son REALLY liked the knife part
He thought it was hilarious! He's not into electronics but I know he likes silly stuff like that (just like any other boys his age!) so I showed this one to him and he laughed every time you used that knife to open a package! Good stuff!
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#12 Reply
Posted by
nuhamind2
on 04 Aug, 2014 05:36
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Looks like the DMM probe should be used like a chopstick
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#13 Reply
Posted by
aargee
on 04 Aug, 2014 05:40
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Dave, Victorinox owns Wenger. I do like the pocket knife much better, I hope you didn't have to buy a stuffed crocodile with that knife.
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#14 Reply
Posted by
dave_k
on 04 Aug, 2014 07:06
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#15 Reply
Posted by
JoeMuc2013
on 04 Aug, 2014 07:13
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Hi Dave,
is this the magnetic core memory production video you were talking about?
221-b and NiHaoMike are probably right, there is another hole in the ribbon flex cable just below the part number print, possibly puncturing traces #12 and/or #13. Traces #20 and #21 were not solder-fixed where the cable was ripped.
Greets,
Joe
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#16 Reply
Posted by
miguelvp
on 04 Aug, 2014 07:20
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Scope is still right side up
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About the core memory.
I watched core planes being made on a field day from school.
The loose cores were poured onto a metal plate with little
slots laid out into an array etched into the surface of the plate.
The plate was vibrated and
the cores would fall into the slots in such a way
that they would stand on edge. The extra cores
would be shaken off the plate.
Then RTV(silicon rubber) was poured over the plate
with the cores on it. Once the RTV set, it was peeled off
with the cores attached to the RTV.
Then workers would pull out fine, straightened wire from
long glass storage tubes and thread the cores sitting
upright on the RTV by hand!
Talk about tedious! There was a lot of labor involved,
and the arrays cost a lot of money to make.
This was back in the early 70's. One of the reasons
core memory was still in production was aerospace & military.
Core was much more robust against radiation & emp and mechanical failure than
other RAM type storage at the time.
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#18 Reply
Posted by
HP-ILnerd
on 04 Aug, 2014 09:41
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That knife is awesome by the way.
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#19 Reply
Posted by
rrmm
on 04 Aug, 2014 11:29
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Anyone know what Siemens computer that core module goes to? Quick count looks like the word size is around 60-64bits and some parity?
Couldn't find much on the web about Siemens' mainframe offerings from the era.
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#20 Reply
Posted by
coppice
on 04 Aug, 2014 13:48
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About the core memory.
I watched core planes being made on a field day from school.
Where was that? Almost all production of core stores went to South East Asia in the very early days, as part of the first wave of moving production to cheap labour countries. It wasn't just about hourly costs, though. This work had a bad effect of people's eyesight, and in places with poor worker protection, they just tossed out and replaced the assembly line workers every couple of years. Not a very noble part of the history of electronics.
I think at the very end they were able to automate the assembly of these things. They certainly pushed up the density a lot. Early 70s core stores were far smaller than early 60s ones. As you said, core continued for a long time in high reliability and radiation sensitive applications. Early DRAM just couldn't match the robustness of core stores, although its density and speed quickly took the lead.
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#21 Reply
Posted by
coppice
on 04 Aug, 2014 14:25
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Hi Dave,
is this the magnetic core memory production video you were talking about?
They are assembling ferrite sheet memory in that video, not core stores.
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#22 Reply
Posted by
lapm
on 04 Aug, 2014 14:54
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Dave thats not a Knife, thats damn sword...
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#23 Reply
Posted by
Dr. Frank
on 04 Aug, 2014 16:07
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Crocodile Jones, get your hair dyed blonde!
Awesome mail bag Monday!
Frank
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#24 Reply
Posted by
SeanB
on 04 Aug, 2014 16:35
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I repaired a few core memories to replace cracked cores. Simplest and easiest was simply to add the new one at the one column end, then unsolder the row and extend it to go through and back to the pad, then route the sense wire through along with inhibit. Worked as the memory core was around 16 bytes of 12 bit info. There was a replacement unit made that used 2 Dallas ram chips to emulate the memory. 2k of memory that only had a tiny amount in use.
I still have some core driver arrays, MPQ6502 transistor arrays that have 2 2N2219A dies and 2 2N2905a dies in the package.