Monday, July 6, 2015

Holiday interruption but some progress on P390 and activity on Pertec

With the big holiday weekend here in the US, I have my daughter's family and their friends over for a belated barbecue which chewed up quite a bit of the day with prep work, shopping and cleanup, in addition to the time together. I didn't get anything done on Sunday.

I am off tomorrow on a business trip thus progress will be quite limited all week.


I was successful using the standalone version of DMKFMT to format the DOS sysres pack, after which I began trying to run the standalone restore program to get the DOS image from virtual tape to the disk.

I had to modify the JCL to run the DOS install, forcing it to skip the initialization step and go right to the restore step. It worked, except for a minor JCL error I had to correct. That is, it worked until it tried to do IO to the virtual disk drive, then it once again failed with the 'invalid drive' error.

I did receive the new CMOS Battery for the server and installed it, now that the post office finally delivered it, several days late compared to when a first class package should have arrived. For several days it was listed as late, but then when it tagged in at my home post office this morning, it was magically adjusted back to 'on time' status. The stats will look really good to top management at the USPS, if they routinely erase evidence of failed service.

Next, I booted the ICKDSF standalone utility tape provided with the P390, which should definitely be able to initialize emulated 3350 packs. This too failed. The good news, however, is that it gave me more information about what is going wrong. It is an unrecoverable error on the alternate track 022B 0000 which is cylinder 555, right where alternate tracks would be if this were a physical 3350 volume.

I researched the error and discovered that the only way to initialize virtual volumes on the P390 is to tell ICKDSF that it is a minidisk, even when it is a full sized 3350. This parameter, MIMIC, will skip the check of the alternate tracks that is causing the problems. Next time I bring up the system, I should be able to initialize the pack properly and from there I should be able to restore DOS/VS.

I got the pack initialized properly as a DOS volume with the VTOC at the end, but the standalone restore program is still crashing with the error (invalid disk drive). I ran out of time to poke at this longer.


I finished the validation that my replaced components had full connectivity - installing a few bridge wires where that was necessary - and am now ready to start testing once again.

The testbed is the raw DC power into the servo board, the two external heatsinks with power transistors, and jumpers to return the -5V, +5V and ground sense returns. This should give me a safe subset to let me bring up the power and test each part of the regulation separately.

When I first brought it up, I saw the op amp smoking and the transistor it feeds. I had thought I had isolated the power sections and was only testing the +20V raw feed, which should have only driven the +10V output. The parts that smoked, however, are on the -20V raw feed side, which produces both -10V and -5V outputs. The last of the regulated supplies, the +5V one, is fed by a +10V raw feed.

I validated that it was not supplying -20V raw, only +20V. That should not be able to energize the circuitry on the negative side - there are just a few diodes and capacitors to ground and I don't see a legitimate path for the +20V to get down to the parts that smoked. This is a good clue even if a bit opaque at first.

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