State of the projects - a new years summary

STATE OF THE PROJECTS - A READER'S REQUEST

One of the loyal readers of this blog suggested that I post this to snapshot the various projects and where I am with each.

RESTORATION OF IBM 1130 FOR SYSTEM SOURCE MUSEUM

The typewriter is the last major item to restore before this system can be returned to its museum in good working order. The remaining tasks for the typewriter:

• Adjust Carrier Return for proper operation
• Fine tune character selection for printing
• Install repaired right margin lever
• Install a ribbon color tape using lacing cord
• Test out operation under motor power
• Test out interface logic in the 1130
• Install typewriter in place

I will also secure the disk arm/heads and other items necessary to keep the machine safe under transport as it is returned to its home in Maryland 

RESTORATION OF MY 1053 CONSOLE FOR MY 1130

I have a few issues with the operation of my 1053 console mostly adjustments. The ribbon color tape broke and I need to repair it as well. Then it will be tested and replaced back on the 1130 system. 

VACUUM TUBE CURVE TRACER IMPROVEMENT

I built a vacuum tube curve tracer using the utracer3+ kit from Ronald Dekker and the heater driver board designed by Stephen Lafferty. When using it to measure real tubes, I discovered two problems. 

The filament voltage sags under high current, which is a problem with where I wired the sense wires since this is a four wire supply that should compensate for resistive losses. 

The currents measured for various tubes seemed to be low compared to the specification sheets. While they matched the shape of the curves properly, I suspect I have to improve the adjustment of the current measuring function to be certain I have accurate values. 

CAPE CANAVERAL SF MUSEUM DISPLAY CONTROLLER BOARD

At the museum, various video displays that run films or other content for visitors have become balky as the contents seem to have been corrupted by various power failures and the passage of time. Too, the displays don't meet the anticipated future needs of the museum for a more powerful display method that can leverage modern monitors and content as well as implement interactive exhibits. 

I chose the PiPresents software to drive the displays, running on Raspberry Pi 3+ processors. Because these run under Linux, they will be susceptible to problems if power is abruptly removed before they have properly shut down. 

I designed a board that uses supercapacitors to give the RPi a few minutes of time to complete a shutdown. This detects power outages and triggers a signal that software will read to immediately issue a shutdown. It has a shutdown button and a start button, although I designed it power up automatically when power is applied as long as the supercapacitors are charged again. A real time clock with battery cell will hold the time and date information between power cycles. 

I am testing out the function, working outward from the MAX38889 chip and circuitry that does the charging, voltage detection, and produces the supply for the rest of the board while running off the capacitor charge. Once satisfied that it works as I intend, I will finalize the PCB and bill of materials so that we can make a controller for each display station at the museum. 

ALTAID 8800 FUN PROJECT

I bought an Altaid 8800 kit but after assembly it was not working properly. I found that the 8080 chip provided had quite a bit of corrosion on about half the leads which is the issue as far as I can tell. When I wiggle the chip into the socket after some cleaning, it works properly for a short bit but not all signals are getting on and off the chip yet. 

Isopropyl alcohol and Deoxit are not breaking through the heavy pin corrosion. I will continue to work on improving connectivity of the pins but my fallback is to buy a replacement 8080 for the kit. 

VIRTUAL 2315 DISK FOR IBM 1130 SYSTEMS

I had engineered a box that is mounted inside an 1130 system which hooks to the internal disk drive. The drive gets a small modification that blocks the disk heads from being lowered onto the surface of the disk inside the 2315 disk cartridge spinning in the drive.

The box watches the signals coming from the disk indicating the rotational speed, sector marks, state of movement of the arm, home position of the arm and others. It also watches the signals coming from the 1130 interface logic which requests arm movement, controls the erase, write and read head circuits and other control lines. 

The box will mount a virtual 2315 cartridge image from among a large set installed on an SD Card in my box. This stores the 1MB disk image into the hardware that will generate the head pulses that otherwise would be detected if the head were flying on the surface and reading the disk. It also captures the new bitstream sent by the interface when the 1130 is writing to a sector, uploading that to the SD Card when the drive is switched off.

What this permits is for the user to insert any old 2315 cartridge into the drive, switch it on, and experience all the sounds and other effects that would exist if the driver were actually reading the cartridge. The arm buzzes as it moves in and out to different cylinder positions and the whir of the motor is audible as the cartridge spins. 

The purpose of this box is to protect the 1130 and its physical cartridges from damage from head crashes, since the supply of new heads and new cartridges is almost nil; the heads are essentially unobtanium but there are a few cartridges that show up on the market from time to time. 

My box operates at the same speeds and timing as the real drive. In fact, the spinning of the inserted cartridge and the movement of the actual arm ensures the timing is faithful. I simply generate some control signals and the bitstream that would be coming from the head were it really down and reading the disk platter in the cartridge. 

I feel good about the state of all the logic but ran into a brick wall getting a Linux loader that would start up the Linux image on the ARM processor side of the board I use. A customized loader is necessary to enable the bridges between the FPGA and ARM sides that are used to load and retrieve the cartridge image. 

I will get back to this when I have some faith that, with new information or someone familiar with the Intel System on a Chip, that I can produce a loader to actually bring up Linux again on the ARM side. 

REASSEMBLY AND ADJUSTMENT OF DOCUMATION 600 - THEN SALE

I have two modern punched card readers - both by Documation - with interfaces to a PC so that I can read and archive data from card decks. My main reader operations at 1000 cards per minute, while the backup unit is a 600 cpm model. I had a failure of the magnetic sensor in the model 1000 which I fixed by replacing it with the model 600 part, then I found an automotive sensor that I believe will work to sense the pulses that reflect the exact movement of cards through the read station. 

I have a bit of reassembly to do, really minor stuff, but the main task remaining is to make all the adjustments so that the reader will feed cards reliably through the machine. Once I get this working I intend to sell or trade it since I have the model 1000 already and need to reduce shop space. 

3178 AND 3179 TERMINALS WORKING WITH P390 MAINFRAME

I have a few IBM terminals which were used to program and operate mainframes in the 1970s. Model 3178 is a green screen 24 x 80 terminal and the 3179 was the color version. These are connected to a 3174 controller that I already restored and work properly in local mode.

My goal is to have these connected to my P390 so that I can fire up the public domain mainframe operating systems that use these terminals - MVS, VM and DOS. In order to do that I have to establish a communications link between the 3174 and the P390, which involves configuring a fast serial communications card that the P390 can drive. I chose the BSC version since the alternative of using VTAM involves a much, much more complex set of mainframe software for which I have limited skills. 

A Cisco router is necessary as an intermediary, which I also own and have configured. I built the cables to connect the 3174 to the router and the router to the card I will eventually install in the P390. I have to get that serial link on the P390 working and properly configured to both OS/2 and the P390 software. This was not a high priority task thus it is sitting on the shelf waiting for when I am ready to resume the project of using the terminals with the P390. 

TELEX 9 TRACK TAPE DRIVE RESTORATION

I have a pair of full size 9 track tape drives, a Telex clone or alternative to 3420 tape drives. I have partially restored one of the two drives but can't yet get it to autoload successfully. The drives have a built in controller, a clone of a 3803, which connects the fat mainframe bus and tag channel cables to a mainframe wishing to use these drives. Until I have a bus and tag interface for the P390 I can't proceed further on this. It is low priority, but when I get spare time I can finish getting the drive to autoload and operate in local mode. 

ADD BUS AND TAG CHANNELS TO P390

I bought several bus and tag cards to add to the P390. It is somewhat complex because the card that went with my version of the P390 was an ISA bus card, however this P390 was built on a PCI based server. I thus need the newer and rarer PCI channel card, which I now own. 

The task is to get this board configured to the IBM xServer, to OS/2 and then to the P390 without killing my working P390 system. It was not a high priority but it is something I will get back to when I have more quiet time.

CDC 2741 CLONE TERMINAL RESTORATION

IBM made a Selectric typewriter based terminal called the 2741 which was used with various timesharing like systems. It was also used to provide additional terminals on an IBM 1130 as a relatively rare feature. I can put the APL typeball on this terminal and connect it through my IO expansion box to the 1130, thus having a convenient way to play with APL and its very different character set and keyboard keys. 

Not a high priority task and might end up not being important enough to me that I will restore this and then sell or trade it. 

SBC6120 PDP8 CLONE ADDITION OF IO EXPANSION BOARD

I have two replicas of a PDP/8 - the PiDP/8 and the SBC6120 which uses an actual microprocessor implementation of the PDP/8. Harris Semiconductor developed the 6120 processor for DEC and it was used in produces like their DecMate. The SBC6120 implements a replica front panel of a PDP/8 and uses that microprocessor to run the code. Both of my replicas work great.

The designer of the SBC6120 also designed a secondary board, the IOB6120, which augmented the machine with quite a few peripheral devices and optional features that were not implemented in the main SBC6120. I built the IOB6120 but it is not working properly with the SBC6120.

There is a header on the SBC6120 and a corresponding header on the IOB6120 for the two to simply plug together, the the IOB6120 setting behind everything inside the cabinet of the replica. In poking around on the internet I found several references to issues that were discovered with the two plugged together, which required some modifications to make them work. However the mods were never disclosed and the original designer does not respond to my several inquiries. 

I suspect that it it requires buffers between the two boards to redrive signals properly although there also could be timing issues that would be thornier to fix. My project would be to build a proper interface buffer after debugging the connection using my logic analyzer, such that I had a fully working SBC6120 plus IOB6120. Obviously not a very high priority but something I don't think will be very hard to do and the result is a pleasing replica in my collection. 

BUILD 2315 ARCHIVING SYSTEM WITH DIABLO DRIVE

I have a Diablo disk drive with the rare single density heads and arm, thus matching the 2315 cartridge exactly. It came from a third party expansion product that hooked to the IBM 1130 to act as an additional disk drive. IBM's product, the 2310, needed the huge three phase 1133 Multiplexer box to hook to an 1130, making it impractical to give me a second drive.

I have good heads to install in this and I am pretty comfortable aligning Diablos drives so I should be able to get this working to read actual 2315 cartridges. I own many dozen cartridges which I could love to read and archive the contents. I used an FPGA to archive the higher density version of the cartridges used on Xerox Alto system; it is pretty easy to create a version for the IBM disk format. 

This is a medium effort task but it will give me access to a ton of 1130 software that sits on those cartridges without me having to risk my 1130's precious heads to read them all. Not an immediate priority but it has the advantage that it frees up the space where I store all those cartridges. They could then mostly be sold or traded. 

ARCHIVE, SHARE AND DISPOSE OF MOST 2315 CARTRIDGES

Once the Diablo archiving system is working from the project above, I would clean and archive each cartridge. The contents can be shared with other 1130 hobbyists, used with the 1130 simulators, and installed on the SD Cards of my Virtual 2315 Cartridge facility. This would be done immediately after I finished developing the archive tool above. 

DEVELOP IO EXPANSION BOX FOR 1130 SYSTEMS THAT DO NOT HAVE SAC CONNECTOR

I had designed an expansion box that connects to the Storage Access Channel (SAC) which is an optional feature on IBM 1130 systems. It is required to hook up the 1133 Multiplexer and thus to use 2310 disks, 1403 printers and other devices that need the 1133. It also connects to the 2250 graphics terminal which was available for the 1130. 

My box intercepts all the IO commands and injects data, interrupts and does cycle stealing on behalf of virtual peripherals. It has an FPGA that communicates over USB Serial to a GUI on a PC that works with the FPGA to implement the virtual peripherals. Among the peripherals it can implement are:

• 1442 reader/punch
• 2501 reader
• 1132 printer
• 1403 printer
• 2310 disk drives
• 1627 plotter
• a shadow console keyboard and printer that captures what is typed on the 1053 and 1130 keyboard
• memory load and dump facility

I did some research and discovered that I could build a version of this that did NOT need the SAC feature. It would be installed inside the covers of the 1130 but do all the same things that my cable connected external box does. 

DISPOSE OF ITEMS I WONT WORK ON IN ORDER TO MAKE SPACE FOR MOVING

I have other items that I own which I realize I will never, ever bump high enough in priority for me to continue working on them. Thus, I will get them ready to sell, trade or dump in order to save space. Some are things that I spent a lot of time and money on, but in my heart I know I won't get back to them. Among them are:

• Hasselblad 500C and EL cameras, many lenses and lots of accessories
• My replica 1130 built as a life size copy but using a gate exact FPGA implementation inside
• Various IBM test boxes, none of which are for systems I have
• Far too many ICs and other parts for any possible future needs
• Designs to implement peripherals with my replica 1130