Wednesday, July 26, 2017

Restoration work on Heath C-3 and on a 1401's card reader


Most of my replacement parts arrived, including the 1626 tube, which I soldered into place. I do have two problems that will require more part orders. First, since I am reverting the design back to the 1629 magic eye tube from the 6E5, it switches the required tube socket from the six pin part I had to remove and an octal socket for the 1629.

Second, part of the first order was wrong. I remember that when I found the 22K 2W resistors on Digikey, I initially ordered 6, the quantity I needed. However, the web site popped up an alert telling me that for the same price I would get 10, because of the volume break at that number. I approved the change but didn't check closely to see that it had changed the type of resistor to a 1/4W 10K that I don't need.

When I was ordering the 22K resistors today, the same pop up was delivered but I cancelled out of it and manually ordered 10 of the desired part. It was now correct and will arrive later this week or over the weekend.

I am awaiting the new 22K resistors, the octal tube socket and the 1629 tube, after which I can wrap up this restoration and begin using the checker.


We have been fighting erratic reading on the 1402 reader that is part of our "Connecticut" system over the past couple of weeks, but today someone noticed that dust was wedged into slots in a plastic disc used with a solar cell to generate the timing pulses for the 12 card rows. With an air compressor and vacuum, the disc was cleaned and our reader is back to proper operation.

We still have a permanent error in core at one address (high in memory, fortunately). We will try varying the core unit voltage in both directions to see if we are right at the edge and failing on the weakest core, or if we have a more pernicious flaw in that core location.

If we can't get the core working, we have a spare 4K core unit that we can swap in. It is a major task, but much easier than disassembling and rethreading a core plane to replace a bad core. 

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