Pink's photos

[madswitcher]

Ferrite core memory!

Crikey that brings back memories  .

I remember working on those core stores when I worked for Computer Automation - 16Kbytes on a single board.  - and before that the early disc drives - they were built into armour plated cases 'cos if they even came of the spindle, they could easily go through the nearest wall.

happy days

 

[Gene Pink]

I wonder if that stuff isn't even older than that or maybe experimental. I had a friend who worked for NCR and IIRC they were using huge "magnetic drum" memories, a variant pre-cursor(?) for hard drives? Some time around then.

By mid-late '70s I was using IC memory chips for my computer. 

JR

I took that giant ROM apart, the pages are inkstamped with full dates, most in june, 1970. They measure 0.006" thick, including the trace. Jpeg to follow.

> OK fixed that for you... may need to move this too,,, but keep the interesting photo's coming.

After getting a feel for the site, this thread is probably better suited in the Brewery. Fell free to move, as I have no intention of actually working on, or repairing, any of this (stuff).  It's just too cool to scrap.

Gene

 

[Gene Pink]

OK, next one. Seriously, if someone cries "uncle", I'll stop.  ;-)

This next board is somehow related to the giant ROM, as all circuit boards on both have a 6-digit number starting in 324. It has something for everybody on it, three form factors of transistors, round can and DIP chips, and HV pentodes. Googling the National Union tube number only comes up with military spare parts lists, described as "vacuum tube, pentode". The military is just so darn secretive. Does anybody have a clue what they might be? Anode cap, 7-pin miniature, 6V fil from pins  2-6, and I believe the G1 is pin 4, or maybe it is the cathode, if they are driving that from the chip.  It doesn't match anything in any of the RCA receiving, or transmitting books here. Didn't look in any of the photo-multiplier books, but you never know, as the voltage is likely about right.

The anodes go to the boards on the right, each channel has 20+ 499K resistors in a string to ground, with the last one tapped to feed the first 709 (709's predated the 741) op amp. Some sort of active regulation. the first feeds the second 709, and that feeds the G-1 on the tube. The anodes also go to that oddball DB-25 housing plug.

Date codes range from 6915 on the Fairchild 709s, to  7249 on one of the DIPs.  with that wide range, either a low-volume product, or from huge stockpiles of parts, as the military may require (and we pay for, but that's another post/rant).

Hmm, maybe this oddball thing really did run photo-multipliers for imaging, and the ROM contained missile directions to Ho Chi Minh's home address. ;-)

Just took another look, maybe it is cathode drive, there are small disc caps to pick up drive current spikes, this would work well to sense load signals, which would also include the possibility of Gieger Mueller tube loads. And six of them would be good to indicate the direction of the source.

To the CIA: Just kidding, this is really just a waffle maker. A simple waffle maker. Or a water heater. Nothing to see here.

Did this post get too verbose? I'm new here, just getting the feel of the place.
Gene

 

[gyraf]

Plasma screen driver? Laser driver?

Oscilloscope output stage?

Magnetron driver?

Electron microscope pre-driver/focus'er?

Top-cap anodes indicate very-high voltages.

We're looking from something requiring so high voltages that it wasn't possible solid-state at the time when 709 IC's were already around..



Any date codes on 709's?

Jakob E.

 

[JohnRoberts]

Any date codes on 709's?

Jakob E.

I remember 709s from late 60s... IIRC something like $70 per op amp.  I recall a tech blew one up by looking at it cross-eyed... (very easy to break).

For that price the IC maker probably signed each one.  8)

JR

 

[mushy]

To the CIA: Just kidding, this is really just a waffle maker. A simple waffle maker. Or a water heater. Nothing to see here.

Did this post get too verbose? I'm new here, just getting the feel of the place.

I'd say you are going to fit in just fine.  MORE CRAP!!!

 

[Gene Pink]

I'd say you are going to fit in just fine.  MORE CRAP!!!

You asked for it.

This one is just a placeholder for tonight, 14" disk pack, not very exciting. What I had in mind isn't ready, good thing I didn't just fire it up after 20 years without checking the aluminum can multi-stage e-lytic. It is reforming right now, one section is not taking voltage too well. After 6 hours, 80uF/350WV is now up to about 200V with a 1mA flow.  This will take overnight to do it right. Gotta love aluminum foil anodizing on the bench.

To answer other questions, 709s were dated 6915. Once I looked close, the pages in the giant ROM are labeled, the first one is "test" with a regular in-out of core pattern, the rest are 0-9, A-Z, and a few more for punctuation marks..96 bits per number or letter? The plot thickens, one of these days, I'll try to decipher it, perhaps a 12X8 matrix for something?

@ madswitcher: 16KB of core??? At 8 bits per byte, that would be over 130,000 cores. You could wear that thing for a winter sweater.

Gene

 

[PRR]

Six-bit code, 14" disk packs..... did you go to CompuServe's yard sale?

 

[gyraf]

..those discs came in beautiful wooden boxes, still have a stack of those  ;D

 

[Gene Pink]

Six-bit code, 14" disk packs..... did you go to CompuServe's yard sale?

I don't know where that disc pack came from originally, a guy named Snake gave it to me when he had to leave town fast. Actually he left the country for good, and for the record, I have absolutely no idea why.

CompuServe had 6 bit words? How did that work, CAP letters only?
_______________________

Now it is two days later, that stubborn 80uF/350V section of a four section cap is finally re-anodized, it graduated "Reform School", but barely. The ESR sucks according to my Heathkit cap bridge with magic eye tube., but it works. And to think, I could have just bought a brand new one for $2.43...........

............from the 1964 B/K replacement parts list on the other side of the schematic.

Unit is a B/K "Model 1076 television analyst". 

This jpeg is the moving dot scanner. A 5" dia. CRT that looks like it is out of an oscilloscope with really pretty blue/purple extremely fast phosphor with no persistence at all, gets scanned NTSC. A transparency is put in front of the blank raster, and the result is picked up by a 9-stage photomultiplier that is narrowly sensitive in that violet wavelength. The result is a scanned video signal of the removable transparency, this is used as a test pattern for the TV under test. There are many transparencies, dots, crosshatch, etc.

Same as a vidicon camera, except completely different. ;-)

*Note that my camera really hated that image, should just be violet and black.

Gene

 

[Gene Pink]

The photo-multiplier has the best seat in the house. It's like a little theatre in there.

 

[JohnRoberts]

You need a yard sale... 8)

JR

 

[PRR]

> CompuServe had 6 bit words?

Internally (all 7-bit ASCII out the modems).

The DEC-10 was a 36 bit machine. In the very earliest days when bits were expensive, SIXBIT code was favored for some alpha strings, notably file-names.

"space, punctuation characters, numbers, and uppercase letters, but no control characters"

Other odd (non-8-bit) CIS oddities. PPN/UID (account numbers) had digits 0-7, never 8 or 9. Hexydecimal is a latecomer.

Note also that many older data tape drives were 7-track. 6-bit would put letters on tape with parity check.

Some mag-stripe cards used sixbit w/parity.

There were variants with shift-in/out codes for another level of characters.

Of course Braille is a 6-bit code.

https://en.wikipedia.org/wiki/Six-bit_character_code

 

[Gene Pink]

Wirewound pots don't have to be linear taper.

This one sure ain't.

Gene

 

[madswitcher]

That disc pack looks remarkably like the old CDC 80Mb cartridges that I used to work on.  The disc drive itself was like a washing machine and the head assembly moved in and out on a voice coil that could take you hand off if you nudged it when setting the heads up.

Computer operators cottoned on to the fact that the top surface was not used for storage and used to write identifiers on it in felt tip pens.  Of course, when you spin the disc up to about 5600 rpm, the powder in the ink creeps, pollutes this disc chamber, gets under  a head and you can take out the complete set of heads.  Even more dramatic on the 300MB version when you had 20 heads to replace and set up. 

if you had a head crash, we used to take the centre spindle out and insert a clock movement so it acted as a discussion piece and a reminder not to write on the top surface again. 

I must dig out some of my old stuff,

Cheers

Mike

 

[Gene Pink]

That disc pack looks remarkably like the old CDC 80Mb cartridges that I used to work on.  The disc drive itself was like a washing machine and the head assembly moved in and out on a voice coil that could take you hand off if you nudged it when setting the heads up.

Mike, does this look familiar? 4" voice coil, 12" scale on the bench for comparison. One head of the original 20 in place. Gotta weigh 80+ pounds.

Gene

 

[Gus]

Scary when an emergency heads retrack happened.
Setting the head looking at tribits with a calibration diskpack what fun
Set the heads and then run a test that move the heads in a rapid way and then check if the heads moved.
Big coils on the CDCs

Worked on CDCs and DEC drives back in the 80's

 

[madswitcher]

Hi Gene,

that's one head assembly, but looks like an Ampex not a CDC.  The CDC ones had an open voice coil with a central core electromagnet IIRC - it was about 40 years ago !!!


/Nostalgia On

So, image you are sitting there with the disc drive open and the disc is spinning in front of you at 5600 rpm.  You are looking at the cat's eyes (calibration pattern) coming off a CE pack (alignment disc pack that costs about $5K in the 70's) and you are tweaking the heads in and out slightly with an Allen wrench while looking at the scope.  Hairy stuff.

These youngsters...........

/Nostalgia off 

 

[Gene Pink]

> that's one head assembly, but looks like an Ampex not a CDC.  The CDC ones had an open voice coil with a central core electromagnet IIRC - it was about 40 years ago !!!

Electromagnet inside the core? I can see how it would work, but I haven't run across that yet. Sounds ineffecienat, but then again, they were using 7400 TTL series with several hundred amp power supplies.


> So, image you are sitting there with the disc drive open and the disc is spinning in front of you at 5600 rpm.  You are looking at the cat's eyes (calibration pattern) coming off a CE pack (alignment disc pack that costs about $5K in the 70's) and you are tweaking the heads in and out slightly with an Allen wrench while looking at the scope.  Hairy stuff.

Sounds like fun. Question: did they have to be aligned in two dimensions? In and out for tracking, and position along the track for timing so the the heads were in phase with each other?

> These youngsters...........

> /Nostalgia off 

Nothing wrong with nostalgia, these youngsters really should know  their roots.

Some transistors off of a board I started to strip tonight  from the '60s, they hadn't really standardized on power transistor mounting configurations yet.

Gene

 

[madswitcher]

Hi again gene,

In terms of tracking, and I am scrapping my memory a bit here, the voice coil moved in and out towards the centre on a set of precision bearings and the electronics worked on sensing the signal when moving from track to track.  The disc had typically 512 sectors per track and each sector had a prescribed format that you laid down magnetically when you formatted the disc.  The format specified the current sector and the next logical sector so you could skip one if the magnetic domains on one were not up to scratch.

A really neat idea was the concept of a 'cylinder', so on a multi platter disc you would read a complete track on the top surface of a platter and then do a head switch to read the underside of the same platter, then the top surface of the next patter down and so on.  The head switch time was a microsecond or less, but the head track to track was milliseconds so you could get really high speed performance from them, albeit at low storage capacities.  Interestingly, the disc controllers I worked on were hard microcoded and very efficient.

Running the diagnostics was fun: there was a particular test called the 'Cresendo'.  Start at cylinder 0 (outside of the disc), seek to cylinder 255 (inside of the disc) , seek to cylinder 1, seek to cylinder 254 and so on.  these babies would do the seek in milliseconds and not falter - amazing engineering.

Cheers

Mike