On 29 Jun, 2007, at 20:37, cctalk-request at classiccmp.org wrote: Yes that's reasonably weird. I particularly like the weirdness of drum where the data spins faster than the drum and it stores even faster rotating data on the same band. Makes my 1301's drums with one read/write head on each bit track seem boring, though the tracks are grouped in fours as it is a 4 bit parallel by 12 digit serial architecture. The 1301 has a neat trick for its day, to transfer an entire band (four tracks, 200 x 48 bit words), it did not wait for the start of the track to come round, it started at the next decade (ten word) boundary to come around, worked up to the end of the band, set its core address back to the original start address (which had to be a multiple of 200) and worked up to the start of the data already transferred. Thank you very much. The plan is to get one of my two machines into a museum one day, hopefully both when I am too old to use it/dead. Almost ten years ago the Computer Conservation Society had plans to get one into the Bletchley Park museum and one into the 'Science Museum' but both of them dropped out - I suspect its because a 1301 takes up too much floor space. Ah! Wire-AND. Would this be negative power rail germanium by any chance? If so I suspect the circuits are basically similar but the nomenclature is different. On the 1301, a logic 1 is -6.3 volts and a logic 0 is 0 volts. When fault finding we usually have one person at the console operating the machine and looking at the logic diagrams calling the circuit references to be checked and one on an oscilloscope out of sight describing the display on the 'scope. Most of us are of course familiar with silicon logic and we get confused by calling out 'high' and 'low' because it is so natural, and we find it so difficult to remember high is 0 and low is 1, so we TRY to call out logic 0 and 1 instead, but it so hard to break old habits. The 1300s had four different tape subsystem options. The 'High Speed' (90kc/s) system, called tape type 1 (because it was the first developed) was a one inch system using Ampex drives, and IIRC, they were TM2s. They had 16 tracks (8 data and 8 CRC), and ran at 150 ips. My machines TM4 system (4 data 6 CRC tracks) was tape type 3 (22.5kc/ s) and was basically the same electronics with some parts removed and the minimum changes to make it store two frames where the high speed system saved one frame. It runs at only 75 ips. It uses Thyrotrons to turn the pinch rollers on and off. It has small vacuum chambers plus swing arms to buffer and measure the amount of buffered tape, the (air damped) sensors on the swing arms being the only things which control the reel motors - too much slack and the reel motor winds some in, too little and it winds some out. Me too, though much of it is too much like my everyday job. Its like in the winter I drive my reasonably modern Jag or BMW to work but in the summer I enjoy driving my 1960s Daimler or Rover, and sometimes it feels like an achievement just to get to work, and if I stop for petrol I have to allow an extra ten minutes to chat to people who come over to admire the car. "They don't make them like that any more" or "My uncle used to have one of those". I even had someone who seemed to offer me 30k for a car insured for only 11.5k. Good. I was lucky enough to buy not just the computers but a load of spares. As yet I've not needed to do much component level repairs. Its the Ampex decks which cause most problems because they are American made, they don't use British components. For the CPU things like light bulbs, the same type were telephone exchanges and cars of the period, which are now classic and hence there is an industry still supplying them. The telephone exchange bulbs crop up on eBay, even sometimes the rarer voltages like 17 volts, and I recently bought almost a hundred 28 volt ones which produce an identical intensity plugged in in place of 24 volt ones. Its the things like the bulbs for the virtual address display (12 miniature projectors, one for each digit 1-8, and letters 'E','L' and 'U' and an underline) which are a problem. They are 6.3 volt 6 watt. I thought I'd cracked it when I picked up some 6 volt car ones rated at 6 watts, assuming that like a 12 volt car system, the charging circuit would run them up to 15 to 20% over-voltage. But they only last about 30 seconds. I've checked the supply and it is only 6.3 volts, I can only assume it must be the enclosed space require a higher operating temperature. Googling has found the GE part number listed as microscope illumination lamps, but it doesn't give the voltage or amperage ratings, and the price was horrendous, so I'm not even sure they really are the right ones, and too tight fisted to take a chance. Maybe if we have a lot of people paying admittance to see the old girl (if she's works on the day) at classic car show I hold at my home in a couple of weeks time. Still, I've bought an old 4 trace HP storage scope (via ebay) on that expected income already, and after only one day's operation it now works for 20 seconds after turning on and the goes clip-clop, clop-clip, repeatedly and so I may have to spend more money and time trying to repair it. Better go to bed now, its 1am, got carried away!