IRIS ATC has a hiccup and the Elliott 803 store fault returns

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Still lots of interest in the Harwell computer and a very busy weekend at the museum

IRIS has a hiccup but may be fixed again

After many months of faultless operation, the past few weeks has seen IRIS, the Air Traffic Control system, randomly rebooting to the point where the system does not stay running for more than an hour. This is certainly as a result of the hot weather over the summer period as the system was normally housed in an air conditioned room when in service. So, Peter V spent most of Saturday with the covers off trying to figure out what the problem might be. The random reboots were normally preceded by an RDI (Radar Data Interface) error message on the console so that was a big clue. Next was to identify the cards involved with the RDI interface, which turned out to be several in both the BEG and RBEG PDP 11/84s. All the cards were removed, the edge connectors cleaned, all ribbon cables checked and then all reseated in the system. All seemed fine until the RBEG was started and then failed at error code 4 on the front panel. The cards previously removed were removed again and refitted, the system powered on and the system finally started up. The system then continued to run for the following hour that was left without incident. So, hopefully the problem has been fixed

Elliott 803 blows a fuse and the store fault returns

Kevin B did the usual start-up process on the Elliott 803 on Saturday, switched on the battery and then the computer, but nothing happened. He repeated the process and still the system did not start. On further investigation one of the fuses in the power supply cabinet had blown. After finding and fitting a suitable replacement the system started up and continued to work well for the rest of the day. However, when Kevin B used the system on Sunday to play some music it started to report random parity errors which went away when the top 8K store was disabled, so something is not right. So Peter O has some more investigations to do when he is next in.

Elliott 803 ALGOL paper tapes

Over the past few weeks, Peter O has been experimenting with getting the Elliott 803 to load and run the ALGOL compiler. This can only run in the full 8K of memory so it is only recently that he has been able to do this for real - He has been loading and using ALGOL on his emulator for some time. One of the biggest problems is the size of the two paper tapes that need to be read in and the likelihood of one or both being torn due to the age of the tape reader and tape itself. Added to that is the time it takes to punch out a new copy (very long). So Peter has devised a way to split the tapes into 4 or 5 smaller tapes making punching replacements much easier and quicker. He has run the tapes in using his emulator but we will wait and see if the 'real' system can do it as well.

WITCH tape reading and archiving

As well as all the hardware, the WITCH system came with a lot programs on 5 hole paper tape. The tape itself while on the surface looks OK, in many cases has deteriorated and become very transparent. So it was very important that we try and get an electronic copy of all the tapes as soon as possible. Peter O offered to help with this as he has a 5 hole tape reader connected to a PC with software to read tapes into files. It was also important that we were able to read what the tape program was, so Peter O wrote a small problem to 'decode' the tapes and produce program listings. The first tape was read and successfully decoded, however it soon became apparent that some of the other tapes had become too transparent and the light sensors could no longer 'see' the holes clearly. Apparently, having thought about the problem, he has informed us, in the best Baldric tradition, that he has 'a cunning plan'. We will have to wait and see!

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