EEVblog #648 - Mailbag

[EEVblog]

Mailbag Monday
Dave opens his mail, outback Australian style...

Franky's Ebay Store
http://stores.ebay.com/99centhobbies

Ten Essential Skills for Electrical Engineers
http://amzn.to/1zJTX3B

WiFi Digital Radio teardown

1970 vintage Magnetic Core Memory!

[221-b]

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

[Homer J Simpson]

[max666]

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:

[Vgkid]

This is a really neat mailbag Monday, gotta love the Magnetic Core memory.

[BravoV]

Lol ... love that knife Dave ! 

[robbak]

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.

[EEVblog]

it is otherwise non-volitaile, so that core will have decades-old data sitting on it.

all 400 words of it 

[pickle9000]

If it has "Nixon sucks" or "Dickhead" on it then it will all be worth it.

[NiHaoMike]

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.

[Stonent]

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.

[iloveelectronics]

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!

[nuhamind2]

Looks like the DMM probe should be used like a chopstick 

[aargee]

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.

[dave_k]

Hey Dave,
What model is the HP printer card? If it's a 615N it will curl up and fail at some point!
There is a well known issue with these cards:
http://en.wikipedia.org/wiki/JetDirect#615n_series_ASIC_issue

If it's a 620N then you're OK 

[JoeMuc2013]

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

[miguelvp]

Scope is still right side up

[creepyoldenj]

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.

[HP-ILnerd]

That knife is awesome by the way.

[rrmm]

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.

[coppice]

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.

[coppice]

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.

[lapm]

Dave thats not a Knife, thats damn sword... 

[Dr. Frank]

Crocodile Jones, get your hair dyed blonde! 

Awesome mail bag Monday!

Frank

[SeanB]

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.