EEVblog #960 - Mystery Merry Mailbag Teardown

A mystery Mailbag teardown item!
Forum:

HDSP-2000 LED Display Application Note:

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[flymypg]

I KNOW THAT PCB TYPE!

When I was a technician in the US Navy in the late '70's we had lots of custom electronics systems implemented as assemblies of small to medium-sized wire-wrapped boards. Of course, the vibration, temperature and humidity cycles on a warship wreaked havoc with wire-wrap, even when perfectly performed.

The kind of PCB shown in the video was rolled out as upgrades for systems that were expected to remain in service for a long time, such as propulsion control systems that needed to last as long as the ship.

The key factor was to avoid the need for field modifications, which were easy to apply to wire-wrapped systems. But even the most stable systems could incur upgrades when other parts of the system changed. The extra isolated PCB pads were there to permit (and simplify) the addition of future bodge wires!

Most often, we'd first cut obsolete traces, next install a wire-wrap pin at designated locations, then run jumper wires to the desired locations, with one end at the part pin and the other at the wire-wrap pin. This permitted urgent changes to be tested and re-worked in the field (on a rocking ship at sea) minimal trauma to the PCB. It also supported easily adding generic DIP parts at intentionally vacant areas.

This retrofit technology became obsolete as the ships involved were retired, and short-run PCBs decreased in cost and improved in quality. The main improvements being (IIRC) PCB design tools running on workstations (instead of mainframes), and pick&place assembly technology.

[stephenmorrish]

As a former IBM inventory controler I can testify to the power of the IBM part number system. If it didn't have a part number it didn't exist. Everything had documentation with the in's and out's of a duck's arse. Suppliers were queuing up to be official recognised by IBM, it was a massive payday if they were willing to jump through the hoops.

I worked in a Hard Drive fab pant in Havant in the UK. I never saw one of these but the Kestrel line was just down from my desk. Kestrel was old school storage drives for mainframe computers still used by banks at the time. I started on Aladdin and 540Mb 3.5 PC drive through to 6.5Gb beasties from the mid to late 90's.

[hpb]

The displays are Hewlett-Packard HDSP-2000 series, originally designed for the HP 9825A. They came in a number of different colors and minor variations. The metal can ICs are all custom IBM hardware. The odd board construction is standard for IBM equipment from the mid-1970s into the 1980s.

[xureality]

you have to do something with the led matrix now, it's way too cool to ignore

[Peter_S_]

The "S Loop" connector is a 1970s style American telephone jack. These were fairly common before modular connectors arrived.

[tohopes]

How to get Dave to open anything: write "Test Equipment" on the outside.

[douro]

FC-CPGA- a technique developed originally at IBM for cheaply and effectively packaging high-performance chips. They were the only ones to use a crimp-on aluminium cap. This technique would continue to be used at IBM into the mid-90s.

[stonent]

IPL means Initial Program Load. The IPL command tells it where the boot up software is stored, so, tape, disks, floppy etc.

[TimoNoko]

IBM System/370 was all made of these tiny boards with regular array of pads and four connectors at the edge. Hundreds of boards and several 100 ampere powersupplies, weighing tons. This design just looked absolutely crazy in comparison with Nova and DEC computers, which had large boards, two feet wide.

[FooneTuring]

Searched that part number, found a page saying "This device was used to diagnose and repair floppy disks/drives. "
My favorite bit: Those 8" floppy go in SIDEWAYS. Wow!
And another page: "It assists with the repair and/or adjusting of IBM floppy drives. A CSE would bring this to diagnose and repair the drive. The test diskette has was written on a highly accurate writer and almost certainly has various tracks written at offsets from the normal locations to allow diagnosis, such as head position misalignment and tracks with a constant signal to permit diagnosis of the read amplifier and associated circuitry."

[johncrunk]

And you are also right that these boards were autorouted. But more than that, the circuitry was mostly constructed using very sophisticated CAD/CAM software and the board layout was just a byproduct of the software. The grid system on the boards also offered a big advantage; engineering changes could be done manually since almost every net on the board had a soldered via. Our development boards would sometimes have hundreds of bodges..

The one megabyte 8 inch floppy disk would contain a "standard" operating system. There would be additional floppies that contained the diagnostic programs for specific machines. The "S loop" and "R loop" are most likely an early version of the IBM token ring networking architecture or something similar. Again, the interfaces tried to be "universal" in design. These testers were used in place of a "front panel" on many of the IBM industrial-type computers since they were meant to be installed in unfriendly locations. In addition, one field engineer could support many machines with a single box.

As for the mechanical design, these were made to be tossed in the back of your car and survive all the punishment that a field engineer would render.

[bloodloss]

Yes this is a Maintenance Device use to troubleshoot both IBM mainframes like the 3081 and 3083 as well as connected devices like the 3380 DASD, 3274, 3705, 1174 Terminal Controllers and many other devices. The MD could also be used to duplicate microcode disks for the devices that still booted from micro code load on disks. I still have the MD that was given to me when they quit using them for onboard diagnostic terminals around the year 2000. I have repaired many an IBM machine or changed its configurations with this device over my twenty plus year career with IBM Mainframes.

[jonathan_herr]

HDSP shift-register displays.. awesome.. those are so uber cool.. you should make a project with them!

[JerrySmithKociak]

Those displays look like HP matrix led displays, namely QDSP-2289 ( I've got some from a military surplus). You can drive them using high speed serial line and transistor keys - to feed in the data (row by row, as far as I remember) to be displayed, they latch the data and patiently wait.

[CuriousMarc]

The IBM silver square packaged SLT modules with the square PCB board pattern date all the way back from 1965 with the introduction of the IBM 360 mainframe - that was totally revolutionary at the time. Then they just kept on going! This technology made it to the very first IBM 5100 "personal" computer in 1975 (just look up a YouTube video for the IBM 5100).

[ikocheratcr]

I have always loved IBM PCB like these, just simply amazing that IBM was manufacturing these in the 70. I also have a couple of ceramic packages like those, but way bigger, and each one has 9 "flip chip"s in them. Blows your mind.

Happy Merry Christmas.

[mikeselectricstuff]

IBM token ring PC network boards used this construction, so not limited to small volume products

[Anzac]

That sort of autorouting and grid layout of the board, sort of makes sense for a prototype board, as it would allow for easier bodge wires, or even adding on of components.

[llhand]

Merry Christmas, Dave. Nice of you to spend a bit of your holiday with us.

[llhand]

The S Loop connector is the old style US Bell telephone plug, so that's probably got a modem inside it. Your brand new snazzy Princess Phone would plug into a socket just like that.
IPL=Initial Program Load, i.e. Boot.

Those were very common circuit boards found in IBM equipment. Also, IBM was the (or one of the) largest manufacturers of integrated circuits at that time. And those metal cans is what all their ICs looked like. The mainframes were full of cards just like those, even my IBM 5100 has that style of printed circuit board in it. I have no idea why, no one else did boards like that I am aware of, but IBM churned them out by the thousands. Those mother board connecters were used everywhere in IBM systems too.They liked to design everything to be easy to replace in the field. Thus the very specialized test equipment!