Rescue 1130: 2014 Pickup of an IBM 1130 System and More

MISSING PAPER TAPE READER POWER SUPPLIES CAN IMPACT A TELETYPE RESTORATION The paper tape reader on the left side of the model 33 ASR teletype has a power supply that feeds it 160VDC for the magnet that advances the tape.

SIGNAL ISSUES TO BE ADDRESSED BY THE CONDITIONER Certain signals produced by the Virtual 2315 Cartridge Facility (V2315CF) that drive logic in the IBM 1130 have significant ringing, bounce and undershoot problems due to the nature of the wiring that ordin…

PCBS AND ALL COMPONENTS CAME TODAY FOR THE CONDITIONER The boards arrived from JLCPCB today, the components that came earlier this week from Digikey.

LEARNED THAT SOMEONE RESTORING ASR-33'S LACKED THE POWER SUPPLY The Teletype ASR-33 comes with a paper tape reader attached to the left side of the body.

GLITCHES CAUSING PROBLEMS IN SOME FUNCTIONS Virtual 2315 Cartridge Facility (V2315CF) attaches to an IBM 1130 computer system, working with the internal 2310 disk drive, to allow mini versions of the disk cartridges (2315) to be used rather than having the

CAPTURE SET UP TO UNDERSTAND WHY WE ARE BUMPING ADDRESSES WEIRDLY The observed symptom was that when I did an XIO Write command with a buffer filled with 321 words whose values were essentially the same as their word number, thus easily identifiable, the…

MISSING DATA DURING A WRITE APPEARS TO BE A MEMORY ADDRESSING ISSUE When writing a sector of 321 words to the Virtual 2315 Cartridge Facility (V2315CF), the first portion of the sector is captured correctly but by the middle of the sector, I see the data…

THE ISSUE I AM INVESTIGATING As I was finishing testing of the Virtual 2315 Cartridge Facility (V2315CF), I was writing a sector of data to verify that my signal quality fixes had resolved earlier problems.

REVAMPED ALL UTILITY PROGRAMS TO USE A GRAPHICAL USER INTERFACE The programs had a mixture of Tk (John Ousterhout's graphical interface that goes with his Tcl language), direct python input and Qt toolkit interfaces.

UPDATESECTOR IS GRAPHICAL EDITOR FOR ONE SECTOR OF A VIRTUAL 2315 This Python program opens a disk file used with the Virtual 2315 Cartridge Facility (V2315CF) allowing the user to edit the contents of one of the sectors on that virtual 2315 disk cartridg…

RESOLUTION OF PREVIOUS ISSUES APPLIED During testing of writing from the IBM 1130 to the Virtual 2315 Cartridge Facility (V2315CF) I had identified two areas of concern.

RESTRUCTURED WRITE TEST PLAN SLIGHTLY In the previous tests, I read in cylinder 0, head 0, sector 0, modified just a few words manually, and then wrote it back to C0 H0 S0.

RAN WITH THE NEW LOGIC, TESTING WRITE IN VIRTUAL MODE Armed with the logic analyzer trace of the exact timing that the Virtual 2315 Cartridge Facility (V2315CF) would see of the two related signals, -Write Clock Phase B and -Write Clock and Data that are…

THE ISSUE I WAS INVESTIGATING The Virtual 2315 Cartridge Facility (V2315CF) attaches to an IBM 1130 computer and works in conjunction with the internal 2310 disk drive of that computer.

BASED ON DISCOVERY OF THE ROOT CAUSE, I CORRECTED THE DESIGN The state machine I developed to capture the data from a write command issued by the IBM 1130 to the disk drive started out of the idle condition based on a couple of conditions.

INSTALLED THE POWER COMPONENTS IN THE PROTOTYPE ENCLOSURE The enclosure has an incorrect opening size for the Virtual 2315 Cartridge Facility (V2315CF) main unit, but I used it to work out the mounting locations for the various power components that fit i…

ENCLOSURE TO MOUNT VIRTUAL 2315 CARTRIDGE FACILITY IN IBM 1130 The Virtual 2315 Cartridge Facility (V2315CF) is installed inside an IBM 1130 computer with the main enclosure, constructed of acrylic, bolted to the top of the internal 2310 disk drive of the…

WRITING DATA EARLIER IN THE CAPTURE OF EACH WORD My logic had been waiting until the last of the twenty bits had been captured - the 16 bits of the data word and then the four error checking code bits that validate the integrity of the data.

RESULTS OF TESTING A WRITE TO THE V2315CF USING MY NEW DETECTION METHOD I loaded a test 2315 cartridge into the Virtual 2315 Cartridge Facility (V2315CF) in virtual mode, so that the IBM 1130 saw the disk drive as ready for activity about 90 seconds after…

POWER FAIL PROTECTION FOR V2315CF INSTALLED At the heart of the Virtual 2315 Cartridge Facility (V2315CF) is RAM that holds the entire contents of a 2315 disk cartridge.

EVALUATING STRATEGY FOR DETERMINING BIT VALUE The IBM 1130 writes to disk alternating values on the -Write Clock and Data signal line, with a 0 always written to -Write Clock and Data during the first half which represents a self clocking pulse and then w…

WHAT I OBSERVED MONITORING THE SIGNALS INVOLVED IN -WRITE GATE In my last post I discussed the circuits that generate the -Write Gate signal from the IBM 1130 disk controller logic that is continually triggering my Virtual 2315 Cartridge Facility (V2315CF)

WRITE STEADILY COMMANDED AS VIRTUAL 2315 CARTRIDGE FACILITY BECOMES READY After I enabled my logic to begin testing the write functionality, because my FPGA logic had a temporary block on it, the WR indicator on the main box of the Virtual 2315 Cartridge…

RESEATED CARDS AND CABLE CONNECTORS IN 1130, RESUMING TESTING I pulled out some of the SLT cards to gain access to gate A compartment C1 of the 1130 where the disk controller logic is housed and where the signal cable from the V2315CF is plugged in.

ONE OF THE VERY FIRST HOME COMPUTER DESIGNS The most well known of the early home computer designs is the Altair 8800, a kit from MITS that was publicized in an article in Popular Electronics on January 1975.

HAD NARROWED THE PROBLEM DOWN IN PRIOR SESSION In the last session, I determined that the problem in the main box of the Virtual 2315 Cartridge Facility (V2315CF) was either in the Lattice FPGA chip on the board or in the path on the PCB between that chip…

SIGNALS BEING OBSERVED AND THEIR PURPOSE The cable that connects the 1130 to the 2310 can carry up to 20 signals on the 24 connector pins, although in the implementation used in the 1130 only 17 are defined, with one of them connected to two pins on the c…

RETEST UNDER VIRTUAL MODE TO BE CERTAIN IT WORKS PROPERLY I ran the same loop seeking in and out by the same number of cylinders, initially 200 then other values - to be certain that the Virtual 2315 Cartridge Facility (V2315CF) is handling seeks properly…

DEBUGGING CAPABILITIES BUILT INTO THE V2315CF The Virtual 2315 Cartridge Facility (V2315CF), built around an FPGA, a DRAM chip and a Raspberry Pi PICO, has a serial debugging output available that logs both status and error messages as the unit does its w…

TESTED LOGIC REFINEMENT FOR SEEK SHADOWING IN REAL MODE The Virtual 2315 Cartridge Facility (V2315CF) monitors the seek commands sent from the IBM 1130 system to the 2310 internal disk drive.

FPGA IN V2315CF UPDATED TO WORK WITH ELECTRONIC SWITCH VERSION The FPGA inside the main box of the Virtual 2315 Cartridge Facility (V2315CF) was loaded with the updated logic that renders the output drivers of the box inert for signals that are directly c…

REVIEWING TERMINATOR CARD FOR SIGNALS ENTERING THE V2315CF MAIN BOX The Virtual 2315 Cartridge Facility (V2315CF) sits in between the IBM 1130 disk controller logic and the internal 2310 disk drive inside the 1130, routing signals into the main box of the…

LOGIC ANALYZER SHOWS SHORT GLITCHES THAT CAN AFFECT STATE MACHINE When looking at the logic analyzer traces I collected while doing seeks with the Virtual 2315 Cartridge Facility (V2315CF), where the internal 2310 disk drive of the IBM 1130 was used in co…

ELECTRONIC SWITCH ADDED FOR IMPORTANT SIGNALS RELATED TO SEEK The Virtual 2315 Cartridge Facility (V2315CF) makes use of a PCB that sits between the signals that normally run between the IBM 1130 disk controller logic and the internal disk drive (2310).

ADJUSTING THE DISK DRIVE SEEK SETTINGS I wired up a number of disk drive signals to the oscilloscope.

CHECKING 257 TRANSISTOR FROM DONOR SLT CARD I put the transistor that I pulled off a spare card and tested it with my curve tracer.

INVESTIGATING THE REASON THE VOICE COIL IS ENERGIZED AT ALL TIMES The internal disk drive of the 1130 has a disk arm that is moved by a linear voice coil, much like an audio speaker.

RESTORED 1130 POWER RAIL LEVEL LEADING TO NEW SYMPTOMS When working on the disk drive attempting to make the adjustments for seek behavior, I checked the voltage at a pin that the Field Engineeering Maintenance Manual (FEMM) suggested be tested.

ASSEMBLED NEW VERSION OF 2310 INTERFACE BOARD The Virtual 2315 Cartridge Facility (V2315CF) has a component that is a board that interconnects the cables from the IBM 1130 disk controller logic, the internal disk drive, and the main V2315CF unit, as well…

TRYING OUT A TERMINATOR AT THE 1130 BACKPLANE TO IMPROVE SIGNAL The +Access Ready signal that is generated by the disk drive in real mode of the Virtual 2315 Cartridge Facility (V2315CF) or by the V2315CF in virtual mode.

STILL FOCUSING ON SIGNAL INTEGRITY FOR V2315CF SEEK I was not happen with the glitching and malformed signals going into the 1130 for the +Access Ready feedback signal.

NEW TERMINATOR BOARD IMPROVES BUT DOES NOT FIX V2315CF SEEK TRACKING The Virtual 2315 Cartridge Facility (V2315CF) watches the control signals between the 1130's internal disk controller and the internal disk drive (named 2310 or 13SD or RAMKIT).

ADJUSTING THE FORWARD CRASH STOP ON THE INTERNAL DISK DRIVE Crash stop when arm is not at 202 Arm against crash stop just past 202 In order to be safe, I changed the stop to a gap of .008", giving the maximum margin for acceleration while still blocking t…

FINISHED MODIFYING TERMINATOR BOARD WITH NEW RESISTOR VALUES The terminator board that fits into the Virtual 2315 Cartridge Facility (V2315CF) main unit is the same one used successfully with the unit in its original role as George Wiley's RK-05 Emulator…

TESTING NEW SHADOWING MECHANISM I loaded the FPGA and PICO of the Virtual 2315 Cartridge Facility (V2315CF) with the updated functionality and repeated the tests from before - using the disk in real mode, issuing seeks of various distances.

SITUATION BEING ADDRESSED When we have loaded a valid mini cartridge into the Virtual 2315 Cartridge Facility (V2315CF) it should remain active regardless of whether we power the disk drive down and back up.